- Email: [email protected]
Nano ZrO2 nanocomposite as an adsorbent for the removal of nitrate from the aqueous solution
Accepted Manuscript Title: Chitosan/Zeolite Y/Nano ZrO2 nanocomposite as an adsorbent for the removal of nitrate from the aqueous solution Author: Abbas Teimouri Shima Ghanavati nasab Niaz Vahdatpoor Saeed Habibollahi Hossein Salavati Alireza Najafi Chermahini PII: DOI: Reference:
S0141-8130(16)30501-3 http://dx.doi.org/doi:10.1016/j.ijbiomac.2016.05.089 BIOMAC 6150
To appear in:
International Journal of Biological Macromolecules
Received date: Revised date: Accepted date:
30-11-2015 1-5-2016 25-5-2016
Please cite this article as: Abbas Teimouri, Shima Ghanavati nasab, Niaz Vahdatpoor, Saeed Habibollahi, Hossein Salavati, Alireza Najafi Chermahini, Chitosan/Zeolite Y/Nano ZrO2 nanocomposite as an adsorbent for the removal of nitrate from the aqueous solution, International Journal of Biological Macromolecules http://dx.doi.org/10.1016/j.ijbiomac.2016.05.089 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
1
Highlights
Removal of nitrate ions (NO3-) by CTS/ZY/Nano ZrO2 nanocomposite as adsorbent was
investigated.
Adsorbent was characterized by N2 sorption (BET), FTIR, SEM and XRD.
Effect of molar ratio, pH, temperature on adsorbent capacity and model of kinetics
and isotherm was investigated.
2
Chitosan/Zeolite Y/Nano ZrO2 nanocomposite as an adsorbent for the removal of nitrate from the aqueous solution Abbas Teimouria,*, Shima Ghanavati nasaba,b, Niaz Vahdatpoora, Saeed Habibollahia, Hossein Salavatia, Alireza Najafi Chermahinic a
Chemistry Department, Payame Noor University, 19395-3697, Tehran, I. R. of Iran Department of Chemistry, Shahrekord University, Shahrekord 115, I. R. of Iran c Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111, I. R. of Iran b
Abstract In the present study, a series of chitosan/Zeolite Y/Nano Zirconium oxide (CTS/ZY/Nano ZrO2) nanocomposites were made by controlling the molar ratio of chitosan (CTS) to Zeolite Y/Nano Zirconium oxide in order to remove nitrate (NO3-) ions in the aqueous solution. The nanocomposite adsorbents were characterized by XRD, FTIR, BET, SEM and TEM. The influence of different molar ratios of CTS to ZY/Nano ZrO2, the initial pH value of the nitrate solution, contact time, temperature, the initial concentration of nitrate and adsorbent dose was studied. The adsorption isotherms and kinetics were also analyzed. It was attempted to describe the sorption processes by the Langmuir equation and the theoretical adsorption capacity (Q0) was found to be 23.58 mg nitrate per g of the adsorbent. The optimal conditions for nitrate removal were found to be: molar ratio of CTS/ZY/Nano ZrO2: 5:1; pH: 3; 0.02 g of adsorbent and temperature: 35 ◦C, for 60 min. The adsorption capacities of CTS, ZY, Nano ZrO2, CTS/Nano ZrO2, CTS/ZY and CTS/ZY/Nano ZrO2 nanocomposites for nitrate removal were compared, showing that the adsorption ability of CTS/ZY/Nano ZrO2 nanocomposite was higher than the average values of those of CTS (1.95 mg/g for nitrate removal), ZY, Nano ZrO2, CTS/Nano ZrO2, and CTS/ZY. Keywords: Chitosan, Zeolite Y, Nano ZrO2, Adsorbent, Nanocomposite, Removal, Nitrate.
1. Introduction In recent years, contamination of nitrate in ground water has become a serious concern globally. Nitrates are used in agriculture because of their good solubility in water and their *
Corresponding author at: Department of Chemistry, Payame Noor University (PNU), Isfahan, P.O. Box 81395-671, Iran. Tel.: +98 31 33521804; fax: +98 31 33521802. E-mail addresses: [email protected], [email protected] (A. Teimouri).
3
nutrient value for plants [1, 2]. The nitrate contamination of water is largely due to great amounts of fertilizers, but human and animal wastes, disposal of untreated sanitary and industrial wastes in an unsafe manner, leakage from septic systems, landfill leachate, animal manure and NO x air stripping waste from air pollution control devices are also other important factors. Ground water has largely been used as a source of drinking water. A high nitrate level in water can lead to a risk for humans, e.g. blue baby syndrome for infants [3, 5]. Especially, nitrate can cause serious health problems including eutrophication and infection diseases, such as cyanosis and cancer of the alimentary canal. When nitrogen from ammonia or other sources is combined with oxygenated water, nitrate is generated [6]. Thereupon, nitrate removal from water is of considerable importance from environment and health points of view [7]. Commonly used methods for nitrate removal from water include different processes [8-10] such as biological denitrification, chemical reduction, reverse osmosis and adsorption. Most of the methods are not effective enough and many attempts have been made to find a nitrate removal method that would be both cost effective and easy to perform. For example, maintaining the biological processes at their optimum conditions is bothersome, and the problems of contamination by dead bacteria have to be solved to make such processes desirable for the safe use in water treatment [11]. Also, current available technologies for nitrate removal are expensive and incompetent, generating additional by-products. However, these traditional technologies do not solve the problem related to the additional nitrate in the environment [12, 13]. For nitrate removal, adsorption has become one of the most economic and efficient methods. The process is superior to many other methods of water reuse due to its low initial cost, low energy requirements, ease of design and the possibility of reusing the adsorbent via regeneration. So, this process has received considerable attention during recent years [14]. Various adsorbents have been tested for nitrate removal from
4
water [15-26]. Usually, nitrate removal by different adsorbents has been employed using micronsized particles, but, over the last few years, nanotechnology has become one of the attractive technologies for water treatment. The advantages of using nano-materials may be derived from their self-assembly, large surface area and enhanced reactivity [27] and so, they can be potentially used for water remediation [28, 29]. It is essential that a novel and economical adsorbent for the treatment of nitrate ions in water be developed. Biosorption has been identified as an efficient procedure because of its low cost and good biocompatibility. Chitosan, a linear copolymer of glucosamine and N-acetyl glucosamine, is easily obtained by thermo-chemical deacetylation of crustacean chitin and is regarded as a superb natural adsorbent due to its amine (–NH2) and hydroxyl (–OH) groups; it may also serve as a coordination site to form complexes with various ions [27]. Natural zeolites, which are hydrated aluminosilicate minerals of a porous structure with invaluable physicochemical features, have also been tested for the removal of water pollutants. The chitosan coated zeolite (Ch-Z) is protonated with either sulfuric or hydrochloric acid and tested for its suitability to capture NO3− from water at 20 and 4 ◦C [31]. Zirconium based adsorbents have been given more attention in recent investigations due to excellent anion adsorption capacities. Zirconia (ZrO2) is an inert inorganic metal oxide material. Its chemical inertness and physical strength can enhance the properties of chitosan when fabricating a composite of ZrO2/chitosan is the goal [32]. Various other methods have been used for removing nitrate anions from water Zr(IV) loaded cross-linked chitosan beads [33], Zr(IV)/sugar beet pulp composite [34], activated carbon and Fe2O3 nanoparticles [35], nanoscale zero valent iron supported on pillared clay [36], polypyrrole nanocomposite [37] and SiO2– FeOOH–Fe nanocomposites [38].
5
In this work, for the first time, we synthesized the CTS/ZY/Nano ZrO2 nanocomposite adsorbent for nitrate removal. We report the preparation, characterization and nitrate adsorption ability of CTS/ZY/Nano ZrO2 as well as the related adsorption isotherms and kinetics. Also, the effects of different experimental conditions, such as different molar ratios of CTS to ZY/Nano ZrO2, the initial pH value of the nitrate solution, adsorbent dose, contact time and adsorption temperature, were investigated. As shown in Scheme 1, the sorption mechanism between the adsorbent and nitrate ions occurs in some positions. Scheme 1.
2. Materials and methods 2.1. Materials Chitosan with 85% deacetylated and medium molecular weight was purchased from Sigma-Aldrich. Zeolite Y was purchased from Zeolyst International Co., Brazil. Zirconium oxide nano powder was obtained from Chinese Changsha Zhonglong Chemical (Group) Co. Ltd, in China. All other chemicals were all of the analytical grade.
2.2. Preparation of CTS/ZY/Nano ZrO2 nanocomposite The Chitosan/Zeolite Y/Nano ZrO2 nanocomposite was prepared by a procedure proposed by Wang et al [33]. 2% ( ) using CTS solution (containing CTS amounts of 0.0660, 0.132, 0.660, 3.30 and 6.60 g) and prepared by adding CTS in 1% ( ) and acetic acid solution. The CTS solution was then added to ZY/Nano ZrO2 (the amount of ZY was twice that of Nano ZrO2) mixture suspension to obtain the nanocomposites and heated at 50 ◦C for 5 h. The molar ratios of CTS to ZY/Nano ZrO2 in the samples were varied by using ratios of 1:10, 1:5, 1:1, 5:1
6
and 10:1, respectively, to obtain the series of nanocomposites. After 1 h, 25% ( ), glutaraldehyde was added to the mixture in a 1:40 volume ratio and stirred for another 1 h at 60 ◦C. The neutralization could be made by adding distilled water and the unreacted glutaraldehyde was removed. The products were then dried in the oven at 60 ◦C for 12 h; then it was powdered.
2.3. Adsorption studies For all batch adsorption experiments, a thermostated shaker was applied. The sample was simulated from nitrate-contaminated water (Nitrate: 20 mg/L, Chloride: 7 mg/L, Sulphate: 13.92 mg/L, Nitrite: 0.16 mg/L, Phosphate: 0.34 mg/L, Ammonium: 0.19 mg/L, Calcium: 50.1 mg/L, Magnesium: 6.08 mg/L, Sodium: 2.3 mg/L, Potassium: 0.39 mg/L) of Langan Fountain, Freydan city, Isfahan, Iran. The effect of the molar ratios of CTS to ZY/Nano ZrO2 on nitrate removal was examined by soaking 0.02 g of the adsorbent in 25 mL of nitrate solutions (20 mg/L, the initial pH of 7) at 35 ◦C for 60 min, respectively. The effect of pH on nitrate removal was calculated by immersing 0.02 g of the adsorbent in 25 mL of 20 mg/L nitrate solutions at 30 ◦C for 60 min in various pH values (2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 and 9.0). The influence of temperature on nitrate removal was studied by immersing 0.02 g of the adsorbent in 25 mL of solutions (20 mg/L, pH 3.0) at different temptatures (10-60 ◦C). The effect of the adsorbent dose on nitrate removal was also studied in 25 mL of solution (20 mg/L, pH 3.0) at 35 ◦C for 60 min, in adsorbent doses (0.005, 0.01, 0.02, 0.03, 0.04). The kinetics of nitrate adsorption onto the synthesized nanocomposite was completed by adding 0.02 g of the adsorbent to 25 mL of nitrate solutions (20 mg/L, pH 3.0) at 35 ◦C. Also, for reviewing the isotherm, 20 mg/L nitrate of solution (25 mL, pH 3.0) was shaken with 0.02 g of the adsorbent at 35 ◦C for 60 min.
7
The capacity of the adsorbed nitrate (mg/g) was calculated as stated in the following equation (1): (
)
(1)
, where Co and Ce are the initial and equilibrium concentrations of the adsorbate (mg/L), respectively. Also, m is the mass of the adsorbent (g) and V is the volume of the solution (L). The concentration of nitrate solutions was measured by a UV-Vis spectrophotometer (HACH DR5000, USA), using the standard methods provided by HACH.
2.4. Characterizations The samples were evaluated by X-ray diffraction (XRD) using a Philips X'PERT MPD X-ray diffractometer (XRD) with Cu Kα (1.5405 Aº). Data sets were arranged over the range of 5º– 90º, with a step size of 0.02º, and a count rate of 3.0º/min. The morphology of the samples was evaluated using a SEM (JSM-6300, Tokyo, Japan) and (Seron Technology AIS 2100, South Korea) Transmission electron microscopy (TEM) images were achieved using a Philips-EM2085 transmission electron microscope with an accelerating voltage of 120.0 kV. IR spectra were recorded on JASCO FT/IR-680 PLUS spectrometer. The BET specific surface areas and BJH pore size distribution of the nanocomposites were evaluated using a Series BEL SORP 18.
2.5. Statistical analysis The collected data representing the percentages of the nitrate removal were analyzed through one-way analysis of variance (ANOVA) using SPSS software. Significant differences between treatments were evaluated using the Tukey HSD test. The level of significance was determined based on a probability of p < 0.05.
8
3. Results and discussion 3.1. FT-IR analysis FT-IR spectra of ZY, CTS, and five nanocomposites with various molar ratios of CTS to ZY are shown in Fig. 1. In the spectrum of pure ZY, as shown in Fig. 1g, the band at 1018 cm -1 was attributed to the stretching vibrations of the Y zeolite structure framework and the band at 3448 cm-1 corresponded to the Si–OH group on the surface of zeolite framework. Also, the band at 1620.88 cm-1 was assigned to the bending vibration of H-O-H bond. The FT-IR spectra of the CTS, as shown in Fig. 1a, illustrated the typical band at 3385 cm-1, which was attributed to the stretching vibrations of the OH and N-H bonds. Also, the band at 1654 cm−1 corresponded to the N-H bond of the acetyl group while the band at 1081 cm−1 - was attributed to C-O-C bond. As can be seen in Fig. 1, the intensity of the bands attached to the CTS (amide I (1654 cm−1) and C-O-C bond (1081 cm−1) in the spectra of the nanocomposites was increased with the corresponding increase in the molar ratio of CTS to ZY/Nano ZrO2. In addition, the band at 2924.53 cm−1, 1620.88 cm-1, and 1018.23 cm-1 became stronger with increasing the molar ratios of ZY. Also, the IR spectra of ZrO2 had a significant band at 542 cm−1 which corresponded to the vibration of the Zr-O bond. This band, which could be seen in the FT-IR spectra of the nanocomposites, was increased with the corresponding increase in the molar ratio of ZY/Nano ZrO2 to CTS [32]. In Fig. 2, the FT-IR spectrum of CTS/ZY/ZrO2 nanocomposite before and after adsorption NO3- has been provided. The band at 1376 cm−1 corresponding to the N–O is related to nitrate adsorption. ●Position for Figure 1.
9
●Position for Figure 2.
3.2. XRD analysis X-ray diffraction (XRD) patterns of the adsorbents were evaluated using Cu Kα radiation (λ=1.5405 Aº). The crystallite size of the crystalline phase was determined by using Scherrer formula [39], with a shape factor (K) of 0.9. It could be defined as: Crystallite size=K.λ/W.cosθ, where W=Wb−Ws, while Wb was the broadened profile width of the experimental sample and Ws was the standard profile width of the reference silicon sample [40]. As shown in Fig 3A, pure ZY typically displayed diffraction peaks at 6.40, 10.20, 23.70, 26.50 and 29.50º, whereas, for CTS, the maximum was seen at 19º. In the XRD of ZrO2, the sharp lines at 30.40, 51.00 and 60.2º were attributed to its tetragonal phase. However, in Fig 3B, a pattern could be detected from the bottom to the top, showing a gradual increase of the ZY peak at 23.70 and 26.50 º as the amount used was increased. It could be, therefore, inferred that the formation of the flocculated structure in nanocomposites was due to the hydroxylated edge– edge interaction of the silicate layers. Also, the reduction in the intensity of the peak with increasing the molar ratios of CTS to ZY/ZrO2 confirmed the formation of an intercalated– exfoliated structure in CTS/ZY/ZrO2 nanocomposites. Accordingly, when CTS was intercalated into ZY interlayer, it ruined the crystalline structure of ZY [46]. Also, as shown in Fig 4, XRD patterns of nanocomposites before and after the adsorption of nitrate were compared. It seemed that the nanocomposite had an amorphous structure before adsorption, but, after the adsorption of nitrate, the presence of sharp peaks indicated the formation of a large crystalline material with a more regular structure.
10
● Position for Figure 3. ● Position for Figure 4.
3.3. SEM analysis Fig. 5 illustrates the SEM images of CTS (a), ZY (b), Nano ZrO2 (c), and CTS/ZY/Nano ZrO2 nanocomposite before (d) and after adsorption (e). Chitosan, due to its wide surface, acted as a bed/support for ZY and Nano ZrO2. From fig. 3d, it could be seen that ZY and Nano ZrO2 were scattered on the surface of CTS. The SEM images indicated that the synthesis of the adsorbent was prospering, confirming both the FT-IR and XRD analysis results. Fig. 5 also shows the SEM images of the sample before and after nitrate adsorption. Compared with the nanocomposite before sorption (Fig. 5d), the nitrate-sorbed nanocomposite (Fig. 5e) had a less porous structure and grooves. ● Position for Figure 5.
3.4. TEM Analysis The morphology of the prepared CTS/ZY/Nano ZrO2 nanocomposite was obtained using TEM images (Fig. 6a and b). It was clear that the nanocomposite exhibited agglomerative morphologies with an irregular shape. Despite partial agglomeration, the size of the agglomerated particles was less than 100 nm. ● Position for Figure 6.
3.5. BET Analysis
11
The nitrogen adsorption/desorption isotherm and the pore size distribution (inset) are shown in Fig. 7. Also, table 1 displays the BET surface area values of the CTS, ZY/Nano ZrO2 and CTS/ZY/Nano ZrO2 nanocomposite. The BET surface area, the average pore diameter, and pore volume were 54.619 m2g-1, 0.949 nm and 0.61 cm3 g−1, respectively. The surface area of the sample was greater than that of CTS, most likely due to the fact that the particles of ZY and Nano ZrO2, which had high surface area, were scattered on the CTS bed, enlarging its surface. Consequently, since the average pore diameter of the nanocomposite was larger than that of nitrate ions, which was 0.396 nm, the anions were able to enter the pores easily. The nanocomposite was also mesoporous with N2 adsorption–desorption isotherms of type IV and an H3 hysteresis loop, according to IUPAC classification. The Type H3 loop, which does not show any limiting adsorption at high p/p°, is usually seen with the aggregates of plate-like particles, giving rise to slit-shaped pores [42]. ● Position for Table 1. ● Position for Figure 7. 3.6. Analysis of nitrate in water Concentration of nitrate in all samples was determined by UV–Visible spectrophotometer (HACH DR5000, USA). NitraVer 3 and NitriVer 6 Hach reagents were added to the solution samples. In the presence of nitrate, the solution formed a pink colour which was measured at the wavelength λ=507 nm. For the determination of the nitrate concentration in solution, a calibration curve was prepared with nitrate solutions of known concentrations.
3.6.1.The effect of molar ratios of CTS to ZY/Nano ZrO2 of nanocomposites on adsorption Fig. 8 illustrates the influence of the molar ratios of CTS to ZY/Nano ZrO2 on the nitrate adsorption capacity of the nanocomposites. As can be seen, the nitrate adsorption capacities were
12
rapidly increased with increasing the molar ratio of CTS to ZY/Nano ZrO2 from 1:10 to 5:1; after that, it was reduced again at 10:1. Also, the adsorption capacity of CTS/ZY/Nano ZrO2 nanocomposite (5:1) was seen to be higher than that of CTS/ZY, CTS/Nano ZrO2, ZY, Nano ZrO2 and CTS. So, the optimum molar ratio was 5:1. It was also observed that the composite adsorbent showed some enhanced removal for the nitrate ions as compared to other components. The affinity of adsorbents for the nitrate ions followed the trend: CTS/ZY/Nano ZrO2>CTS/ZrO2>CTS/ZY>ZrO2>CTS>ZY, indicating that the combination of the components provided a great synergistic effect that led to the enhanced removal of the nitrate ions from aqueous solutions. As can be seen in Scheme 1, the composition of chitosan, zeolite and zirconium oxide eliminated nitrate ions througth hydrogen bond formation and electrostatic interactions from aqueous solutions. Chitosan also plays an important role in the removal of nitrate. The adsorption by chitosan could be attributed mainly to their surface, which contained functional groups such as hydroxyl and amino groups. Such chemical groups are the main factor responsible for adsorption anions (by electrostatic attraction). This shows that at acidic pH, the surface of the chitosan was predominated by positive charges (NH2 to NH3+); thus, the surface had a high positive charge density; uptake of negatively charged nitrate ions would be high. On the other hand, zeolite Y with a Faujasite structure could not have a suitable adsorbent for anions, but, with the adsorption of organic materials, it would become a better adsorbent. The link between nitrate ions and OH2+ zeolite can be expected. It is notable that chitosan zirconium oxide composite can adsorb nitrate anions; however, since zeolite can react with nitrate ion and therefore, the rate of nitrate elimination is increased with the addition of zeolite to composite.
13
● Position for Figure 8.
3.6.2. The effect of pH value on adsorption Another considerable factor affecting the adsorption capacity is the pH of the analyte solutions. The influence of the pH value of the sample solution on the nitrate adsorption capacity is shown in Fig. 9. It can be obviously seen that when the pH value of the nitrate solution was increased from 2 to 3, the removal percent was also increased from 37.00 to 42.50%. After that, from 3 to 9, the removal percentage was decreased to around 10% for CTS/ZY/Nano ZrO2 nanocomposite. One possible method for the adsorption of nitarte may be the electrostatic interaction between the NH3+ groups of CTS and the nitrate anion (they formed the ion pair). So, an acidic pH value is needed to provide –NH3+ groups in the CTS structure, thereby helping the enhancement of nitrate adsorption. At a pH value above 7, the hydroxyl ions may compete with the nitrate anions, resulting in a gradual decrease in nitrate uptake, as shown above. On the other side, the pHzpc of adsorbent was determined at 4. As expected, at pH above 4, the adsorbent surface becomes negatively charged, reducing the attraction of the nitrate anions and electrostatic interaction on the negative surface of the adsorbent. At a pH below 4, the adsorbent surface becomes positively charged, intensifying the electrostatic interaction. ● Position for Figure 9.
3.6.3. The effect of temperature on adsorption The relation between the temperature and the percentage removal of the adsorbent is shown in Fig. 10. The percentage removal of the adsorbent was increased from 35 to 40 with
14
increasing the temperature from 10 to 35 ◦C; after that, it was reduced strongly from 40 to 50 ◦C. So, 35 ◦C was selected as the optimum temperature. ● Position for Figure 10.
3.6.4. The effect of the adsorbent dose on adsorption The influence of the adsorbent dose on nitrate removal at the nitrate concentration of 20 mg/L, pH of 3 and the temperature of 35 ◦C is illustrated in Fig. 11. It was shown that the removal percentage of nitrate was increased from 22.5% to 40% with the increase in the adsorbent dose from 0.005 to 0.02 g/25 mL, respectively. It was also seen that after a dose of 0.02 g, there was a sharp decline in the percentage removal. In fact, with increasing the amount of the adsorbent, accumulation of adsorbent particles on each other could reduce the rate of removal. Therefore, the optimum dose was chosen to be 0.02 g/25.00 mL. ● Position for Figure 11.
3.6.5. Adsorption kinetics The effect of contact time on the removal percentage of nitrate by the CTS/ZY/Nano ZrO2 nanocomposite was investigated. It turned out that the adsorption equilibrium of nitrate on the nanocomposite was accomplished in 60 min. So, for the test, an adsorption time of 60 min was chosen for the adsorption isotherms to ensure that the adsorption equilibrium was achieved. Two simplified kinetic models, including pseudo-first-order and pseudo-second-order equations, were checked out. The rate constant of adsorption can be defined using the pseudo-first-order equation given by Langergren [43]: (
)
(2)
15
,where k1 is the pseudo-first-order rate constant (min−1), and qe and qt are the amounts of nitrate adsorbed (mg/g) at equilibrium and at time t (min). The pseudo-second-order equation, based on equilibrium adsorption, can be defined as [44]: (3) ,where k2 (g mg−1 min−1) is the rate constant of the pseudo-second-order adsorption. In Fig. 12, the linear plots of log (qe−qt) versus t and (t/qt) versus t are shown for pseudo-first-order and pseudo-second-order models, respectively. The rate constants k1 and k2 could be calculated from the plot of the experimental data. The correlation coefficients R2 of the pseudo first-order model was 0.9385 and for the pseudo-second-order model, it was 0.9950 (see Table 2). This showed that the adsorption of nitrate on adsorbent could be better defined by the pseudo-secondorder, rather than the pseudo-first-order. This also revealed that the adsorption of nitrate onto the nanocomposite was controlled by chemical adsorption. In chemical adsorption, It is supposed that the adsorption capacity is proportional to the number of active sites occupied on the nanocomposite surface [45]. ● Position for Figure 12. ● Position for Table 2.
3.6.6. Adsorption isotherms The adsorption capacity of nitrate by adsorbent was investigated at different nitrate concentrations and at 35 ◦C for samples. The results illustrated a strong rise in adsorption capacity as the nitrate concentration was increased from 5 to 200 mg/L for the nanocomposite. It was found that the nitrate adsorption capacity of the adsorbent was increased by enhancing the
16
nitrate concentration. But, increasing the initial concentration of nitrate beyond 80 mg/L led to a gradual growth in the adsorption capacity of the adsorbent. The adsorption process is commonly explained by two isotherm equations, namely, the Langmuir and the Freundlich equations [40], which are brought below, respectively: (4) ⁄
(5)
,where qm (mg/g) and b (L/mg) are Langmuir isotherm coefficients and qm indicates the maximum adsorption capacity. Kf (mg/g) and n are also the Freundlich constants representing adsorption capacity and adsorption intensity, respectively. The Langmuir and Freundlich adsorption isotherm for CTS/ZY/ZrO2 nanocomposite is shown in Fig. 13. The Langmuir isotherm accounted for the monolayer cover of the nitrate on the surface of nanocomposite and the values of R2 and qm for the nanocomposite were 0.993 and 23.58, respectively. On the other hand, the value of R2 in Freundlich model for the nanocomposite was 0.8347. Therefore, the adsorption of nitrate on nanocomposite did not fit the Freundlich isotherm (see Table 3). In addition, a comparison of adsorption capacity (mg/g) and other experimental conditions of some different sorbents for nitrate removal is shown in Table 4. One of the substantial preferences of adsorbents in operation is the possibility of reuse, without any notable loss in the sorption ability. The adsorbents were used in 4 runs and after each run, they were separated by filtration and washed twice with 5 ml NaOH (NaOH was used as the desorption agent because it helped the release of nitrate ions bonded to the amino groups on CTS chains, thereby allowing them to return to the initial state. It was washed with deionised water severally and dried in an oven at 80 ºC for about 5 h. The recovered adsorbent could then be reused in the next run. A comparison of the removal percentage in four sequential runs
17
(31.9%, 25.8%, 24.7% and 17.7%) showed that the adsorbent could be reused several times without any considerable loss of its sorption ability.
● Position for Figure 13. ● Position for Table 3. ● Position for Table 4.
4. Conclusions In this research, a novel low-cost biosorbent, chitosan/Zeolite Y/Nano ZrO2 nanocomposite material, was prepared using environmentally friendly and cheap chitosan, zeolite and zirconium oxide. The results showed that it could effectively eliminate nitrate under acidic conditions via the chelation between No3− and the amine group of complex. It was also found that the nitrate adsorption process was dependent on the molar ratios of CTS to ZY/Nano ZrO2, the initial pH value of the nitrate solution and temperature. By controlling these parameters, optimal conditions for nitrate adsorption were obtained. The adsorption kinetics were seen to obey the pseudo-second-order model, and the isotherm followed the Langmuir monolayer model. Compared with CTS, ZY, Nano ZrO2, CTS/Nano ZrO2 and CTS/ZY, the CTS/ZY/Nano
ZrO2 nanocomposite
had
higher
adsorption
capacity.
Therefore,
nanocomposite could be efficiently used as an adsorbent for the elimination of nitrate.
Acknowledgements
the
18
We gratefully acknowledge the financial assistance provided by the Payame Noor University in Isfahan Research council (Grant # 62370). We also appreciate Isfahan University of Technology. The authors would like to thank Dr. H. Jalali for correcting language problems.
References [1] J.F. Power, J.S. Schepers, Agric. Ecosyst. Environ. 26 (1989) 165–187. [2] E.V.S.P. Rao and K. Puttanna, Curr. Sci. 79 (2000) 1163-1168. [3] M. Islam and R. Patel, Desalination 256 (2012) 120-128. [4] L. Knobeloch, B. Salna, A. Hogan, J. Postle, H. Anderson, Environ. Health Perspect. 108 (2000) 675–678. [5] D.S. Powlson, T.M. Addiscott, N. Benjamin, K.G. Cassman, T.M. de Kok, H. van Grinsven, J. L. L Hirondel, A.A. Avery, C. van Kessel, J. Environ. Qual. 37 (2008) 291–295. [6] I.D. Patil, M. Husain, V.R.Rahane, Int. J. Mod. Eng. Res. 3 (2013) 346-349. [7] A. Elmidaoui , F. Elhannouni, M.A. Menkouchi Sahli, L.Chay, E. Elabbassi, M. Hafsi, D. Largeteau, Desalination 136 (2001) 325–332. [8] J.B.K. Park and R.J. Craggs, Bioresour. Technol. 100 (2009) 3175-3179. [9] J.F. Li, Y.M. Li, and Q.L. Meng, J. Hazard. Mater. 174 (2010) 188-193. [10] J.J. Schoeman and A. Steyn, Desalination 155 (2003) 15-26. [11] M. Chabani, A. Amraneb, A. Bensmaili, Chem. Eng. J. 125 (2006) 111–117. [12] M.I.M. Soares, Water Air Soil Pollut. 123 (2000) 183–193. [13] C.D. Rocca, V. Belgiorno, S. Meric., Desalination 204 (2007) 46–62. [14] C. Namasivayam, K. Kadirvelu, Biores Tech 21 (2001) 381-387. [15] Y. Cengeloglu, A. Tor, M. Ersoz, G. Arslan, Sep. Purif. Technol. 51 (2006) 374–378.
19
[16] A. Bhatnagar, M. Ji, Y.-H. Choi, W. Jung, S.-H. Lee, S.-J. Kim, G. Lee, H. Suk, H.-S. Kim, B. Min, S.-H. Kim, B.-H. Jeon, J.W. Kang, Sep. Sci. Technol. 43 (2008) 886–907. [17] K. Mizuta, T. Matsumoto, Y. Hatate, K. Nishihara, T. Nakanishi, Bioresour. Technol. 95 (2004) 255–257. [18] N. Öztürk, T.E. Bektas, J. Hazard. Mater. B112 (2004) 155–162. [19] Y. Xi, M. Mallavarapu, R. Naidu, Appl. Clay Sci. 48 (2010) 92–96. [20] K. Hosni, E. Srasra, Inorg. Mater. 44 (2008) 742–749. [21] M.M. Socías-Viciana, M.D. Urena-Amate, E. González-Pradas, M.J. García- Cortés, C. López-Teruel, Clay Clay Miner. 56 (2008) 2–9. [22] M. Islam, R. Patel, J. Hazard. Mater. 169 (2009) 524–531. [23] M. Islam, P.C. Mishra, R. Patel, J. Environ. Manage. 91 (2010) 1883–1891. [24] Zh. Feng, W. Wei, L. Wang, R. Hong, RSC Adv. 5 (2015) 96911-96917. [25] Ying Li, Xiaoyan Lin, Xiurong Zhuo, Xueguang Luo, J. Appl. Polym. Sci. 128 (2013) 2746–2752. [26] A. Sowmya, S. Meenakshi, Int. J. Biol. Macro- mol. 64 (2014) 224-232. [27] K. Hristovski, A. Baumgardner, P. Westerhoff, J. Hazard. Mater., 147 (2007) 265–274. [28] X. Zhao, J. Wang, F. Wu, T.Wang, Y. Cai, Y. Shi, G. Jiang, J. Hazard. Mater., 173 (2010) 102–109. [29] A. Bhatnagar, E. Kumar, M. Sillanpää, Chem. Eng. J. 163 (2010) 317–323. [30] A. Teimouri, Sh. Ghanavati Nasab, S. Habibollahi, M. Fazel-Najafabadi and A. Najafi Chermahini, RSC Adv. 5 (2015) 6771- 6781. [31] M. Arora, N.K. Eddy, K.A. Mumford, Y. Baba, J.M. Perera, G.W. Stevens, Cold Regions Sci. Technol. 62 (2010) 92–97.
20
[32] H. Jiang, P. Chen, Sh. Luo, Xinman Tu, Q. Cao, M. Shu, J. Appl. Polym. Sci. 284 (2013) 942–949. [33] A. Sowmya, S. Meenakshi, Int. J. Biol. Macro- mol. 69 (2014) 336-343. [34] M. L. Hassan, N. F. Kassem, A. H. Abd El-Kader, J. Appl. Polym. Sci. 117 (2010) 2205– 2212. [35] N. Mehrabi, M. Soleimani, M. Madadi Yeganeh, H. Sharififard, RSC Adv.5 (2015) 5147051482. [36] Y. Zhang, Y. Li, J. Li, L. Hu, X. Zheng, Chem. Eng. J. 171 (2011) 526– 531. [37] H. Pahlavanzadeh, R. Katal, H. Mohammadi, J. Ind. Eng. Chem.18 (2012) 948–956 [38] E. Bekhradinassab, S. Sabbaghi, Desalination 347 (2014) 1–9. [39] S. L. Sun and A. Q. Wang, J. Hazard. Mater. 131 (2006) 103–111. [40] K. Periasamy and C. Namasivayam, Waste Manage. 15 (1995) 63–68. [41] H. L. Liu, X. F. Sun, C. Q. Yin and C. Hu, J. Hazard. Mater. 151 (2008) 616–622. [42] K. S. W. Sing, D. H. Everett, R. A. W. Haul, L. Moscou, R. A. Pierott, J. Rouquerol, T. Siemieniewska, Pure & Appl. Chem. 57 (1985) 603-619. [43] S. Lagergren. Kungliga Svenska Vetenskapsakademiens Handlingar 24 (1898) 1–39. [44] Y.S. Ho, G. McKay. Process Biochem. 34 (1999) 451–465. [45] A. Özer, G. Dursun, J. Hazard. Mater. 146 (2007) 262–269. [46] Q. Hu, N. Chen, Ch. Feng, W. Hu, Appl. Surf. Sci. 347 (2015) 1–9. [47] Y. Xi, M. Mallavarapu, R. Naidu, Appl. Clay Sci. 48 (2010) 92–96. [48] A. Bhatnagar, M. Ji, Y.-H. Choi, W. Jung, S.-H. Lee, S.-J. Kim, G. Lee, H. Suk, H.-S. Kim, B. Min, S.-H. Kim, B.-H. Jeon, J.-W. Kang, Sep. Sci. Technol. 43 (2008) 886–907.
21
[49] K. Mizuta, T. Matsumoto, Y. Hatate, K. Nishihara, T. Nakanishi, Bioresour. Technol. 95 (2004) 255–257. [50] P.C. Mishra, R.K. Patel, J. Environ. Manag. 90 (2009) 519–522. [51] A. Rezaee, H. Godini, S. Dehestani, A. Khavanin, Iran. J. Environ. Health Sci. Eng. 5 (2008) 125–130. [52] M.F.A. Taleb, G.A. Mahmoud, S.M. Elsigeny, E.S.A Hegazy, J. Hazard. Mater. 159 (2008) 372–379. [53] S. Chatterjee, S.H. Woo, J. Hazard. Mater. 164 (2009) 1012–1018. [54] M.L. Hassan, N.F. Kassem, A.H.A. El-Kader, J. Appl. Polym. Sci. 117 (2010) 2205–2212. [55] H. Demiral, G. Gündüzog˘lu, Bioresour. Technol. 101 (2010) 1675–1680. [56] A. Bhatnagara, E. Kumarb, M. Sillanpääc, Chem. Eng. J. 163 (2010) 317–323. [57] S. Chatterjee, D. S. Lee, M. W. Lee, S. H.Woo, J. Hazard. Mater. 166 (2009) 508–513. [58] R. Saad, Kh. Belkacemi, S. Hamoudi, J. Coll. Int. Sci. 311 (2007) 375–381. [59] R. Saad, S. Hamoudi, Kh. Belkacemi, J Porous Mater. (2008) 15 315–323.
22
Scheme 1. Proposed sorption mechanism between the adsorbent and nitrate ions. Fig. 1. FTIR spectra of a) CTS; the nanocomposites with the molar ratios CTS to ZY/Nano ZrO 2; b) 10:1; c) 5:1; d) 1:1; e) 1:5; f) 1:10; and g) ZY. Fig. 2. FTIR spectra of a) CTS/ZY/Nano ZrO2 nanocomposite before adsorption and b) after nitrate adsorption. Fig. 3. (A)- XRD patterns of a) Nano ZrO2; b) ZY; and c) CTS. (B)- XRD patterns of CTS/ZY/Nano ZrO2 nanocomposite with different molar ratios: a) 10:1; b) 5:1; c) 1:1; d) 1:5; and e) 1:10. Fig. 4. XRD patterns of a) CTS/ZY/Nano ZrO2 nanocomposite before adsorption and b) after nitrate adsorption with the molar ratio of 5:1. Fig. 5. SEM images of a) CTS; b) ZY; c) Nano ZrO2; d) nanocomposite before adsorption and e) after nitrate adsorption. Fig. 6. TEM images of the CTS/ZY/Nano ZrO2 scaffolds. Fig. 7. N2 adsorption–desorption isotherm of CTS/ZY/Nano ZrO2. Inset: Pore size distribution using BJH method. Fig. 8. The effect of the molar ratios of CTS to ZY/ZrO2 on the adsorption capacity of the nanocomposites for nitrate. Concentration: 20 mg/L; sample range: 0.02 g/25.00 mL; natural pH; temperature: 30 ◦C; and equilibrium time: 60 min. Fig. 9. The effect of the pH values on the adsorption capacity of CTS/ZY/ZrO 2 nanocomposite for nitrate: nitrate concentration: 20 mg/L; sample range: 0.02 g/25.00 mL; pH range: 2–9; temperature: 30 ◦C; and equilibrium time: 60 min. Fig. 10. The effect of the temperature on the adsorption capacity of the CTS/ZY/Nano ZrO 2 nanocomposite for nitrate. Nitrate concentration: 20 mg/L; sample range: 0.02 g/25.00 mL; pH: 3; temperature: 10–60 ◦C; and equilibrium time: 60 min. Fig. 11. The effect of the adsorbent dose on the percentage removal of nitrate anions at nitrate concentration: 20 mg/L; pH: 3; temperature: 35 ◦C; and equilibrium time: 60 min. Fig. 12. a) Pseudo-first order kinetic and b) Pseudo second order kinetic for nitrate adsorption by CTS/ZY/ZrO 2 nanocomposite (80 mg.L-1 nitrate solution). Fig. 13. a) Langmuir adsorption isotherm and b) Freundlich adsorption isotherm for CTS/ZY/ZrO2 nanocomposite.
23
Table 1 BET surface area values of CTS/ZY/Nano ZrO2. BET surface Pore volume Catalyst area (m2g-1) (cm3 g−1) Chitosan 4 0.10 ZY/Nano ZrO2 CTS/ZY/Nano ZrO2
Average pore diameter (nm) 3.5
92
0.23
4
54.619
0.61
0.949
24
Table 2 Kinetic parameter for the sorption of NO3− anion on to a CTS/ZY/ZrO2 nanocomposite. No3− qe (exp) Pseudo-first-order Pseudo-second-order C0 (mg/g) qe (cal) (mg/g) K1 (1/min) R2 qe (cal) (mg/g) K2 (g/mg min) (mg/L) 80 120 160 200
22.50 25 27 30
34.70 38.12 41.15 47.78
0.000143 0.000148 0.000141 0.000154
0.9385 0.8689 0.8478 0.8248
23.10 28.12 31.15 35.78
0.011833 0.01177 0.01183 0.01180
R2
0.9950 0.9884 0.9950 0.9935
25
Table 3 Values of different isotherm parameters. No3− sorption Langmuir isotherm qm (mg/g) b (L/mg) R2
23.58 0.1557 0.9930
Freundlich isotherm Kf 1/n R2
4.8745 0.3141 0.8347
26
Table 4 A comparative evaluation of adsorption capacity (mg/g) and other experimental conditions of some different adsorbent for nitrate removal. Experimental conditions Amount References Adsorbent adsorbed Zn/Al chloride layered double pH: 6.0 85.4% 3 hydroxide Concentration range: 10 mg/L Temperature: 25 ◦C hydroxyapatite pH: 6.0 21 mg/g 23 Concentration range: 100 mg/L Temperature: 50 ◦C Granular chitosan-Fe3+ complex pH: 5.0 8.35 mg/g 46 Concentration: 50 mg/L Temperature: 25 ◦C Halloysite pH: 5.4 0.54 mg/g 47 Concentration: 100 mg/L Room Temperature ZnCl2 treated coconut granular pH: 5.5 10.2 mg/g 48 activated carbon Concentration range: 5–200 mg/L Temperature: 25 ◦C Untreated coconut granular activated pH: 5.5 1.7 mg/g 48 carbon Concentration range: 5–200 mg/L Temperature: 25 ◦C Bamboo powder charcoal pH: n.a 1.25 mg/g 49 Concentration range: 0-10 mg/L Temperature: 10 ◦C Commercial activated carbon pH: n.a 1.22 mg/g 50 Concentration range: 0-25 mg/L Temperature: 15 ◦C Mustard straw charcoal pH: n.a 1.30 mg/g 50 Concentration range: 0-25 mg/L Temperature: 15 ◦C Impregnated almond shell activated pH: 6.2 16-17 mg/g 51 carbon Concentration range: 10-50 mg/L Temperature: 20 ◦C Polypropylene-g-N,N-dimethylamino pH: n.a 12.5 mg/g 52 ethylemthacrylate) graft copolymer Concentration range: 25–100 mg/L Temperature: 25 ◦C Chitosan hydrogel beads pH: 5.0 90.7 mg/g 53 Concentration range: 25–1000 mg/L Temperature: 30 ◦C Zr(IV)-loaded sugar beet pulp
activated carbon prepared from sugar beet bagasse
nano-alumina
pH: 6.0 Concentration: n.a Temperature: 25 ◦C pH: 3.0 Concentration range: 10–200 mg/L Temperature: 45 ◦C pH: 4.4 Concentration range: 1–100 mg/L Temperature: 25 ◦C
63 mg/g
54
27.55 mg/g
55
4.0 mg/g
56
27
cross-linked chitosan beads conditioned with sodium bisulfate
pH: 5.0 Concentration: 500 mg/L Temperature: 30 ◦C
104.0 mg/g
57
ammonium-functionalized MCM-48
pH < 8, Concentration: 300 mg/L Temperature: 25 ◦C
27.6 mg/g
58
ammonium-functionnalized mesoporous silicas
pH = n.a, Concentration: 130 mg/L Temperature: 25 ◦C
46.5 mg/g
59
CTS/ZY/Nano ZrO2 nanocomposite
pH: 3.0 Concentration: 20 mg/L Temperature: 35 ◦C
23.58 mg/g
Present study
28
Scheme 1. Proposed sorption mechanism between the adsorbent and nitrate ions
Fig. 1. FTIR spectra of a) CTS; the nanocomposites with the molar ratios CTS to ZY/Nano ZrO 2; b) 10:1; c) 5:1; d) 1:1; e) 1:5; f) 1:10; and g) ZY.
29
Fig. 2. FTIR spectra of a) CTS/ZY/Nano ZrO2 nanocomposite before adsorption and b) after nitrate adsorption.
Fig. 3. (A)- XRD patterns of a) Nano ZrO2; b) ZY; and c) CTS. (B)- XRD patterns of CTS/ZY/Nano ZrO2 nanocomposite with different molar ratios: a) 10:1; b) 5:1; c) 1:1; d) 1:5; and e) 1:10.
Fig. 4. XRD patterns of a) CTS/ZY/Nano ZrO2 nanocomposite before adsorption and b) after nitrate adsorption with the molar ratio of 5:1.
30
a
b
c
d
e
Fig. 5. SEM images of a) CTS; b) ZY; c) Nano ZrO2; d) nanocomposite before adsorption and e) after nitrate adsorption.
31
a
b
Fig. 6. TEM images of the CTS/ZY/Nano ZrO2 nano-adsorbent.
Fig. 7. N2 adsorption–desorption isotherm of CTS/ZY/Nano ZrO2. Inset: Pore size distribution using BJH method.
Fig. 8. The effect of the molar ratios of CTS to ZY/ZrO2 on the adsorption capacity of the nanocomposites for nitrate. Concentration: 20 mg/L; sample range: 0.02 g/25.00 mL; natural pH; temperature: 30 ◦C; and equilibrium time: 60 min.
32
Fig. 9. The effect of the pH values on the adsorption capacity of CTS/ZY/ZrO 2 nanocomposite for nitrate: nitrate concentration: 20 mg/L; sample range: 0.02 g/25.00 mL; pH range: 2–9; temperature: 30 ◦C; and equilibrium time: 60 min.
Fig. 10. The effect of the temperature on the adsorption capacity of the CTS/ZY/ZrO 2 nanocomposite for nitrate. Nitrate concentration: 20 mg/L; sample range: 0.02 g/25.00 mL; pH: 3; temperature: 10–60 ◦C; and equilibrium time: 60 min.
Fig. 11. The effect of the adsorbent dose on the percentage removal of nitrate anions at nitrate concentration: 20 mg/L; pH: 3; temperature: 35 ◦C; and equilibrium time: 60 min.
33
a
b Fig. 12. a) Pseudo-first order kinetic and b) Pseudo second order kinetic for nitrate adsorption by CTS/ZY/ZrO 2 nanocomposite (80 mg.L-1 nitrate solution).
34
a
b Fig. 13. a) Langmuir adsorption isotherm and b) Freundlich adsorption isotherm for CTS/ZY/ZrO2 nanocomposite.
S0141-8130(16)30501-3 http://dx.doi.org/doi:10.1016/j.ijbiomac.2016.05.089 BIOMAC 6150
To appear in:
International Journal of Biological Macromolecules
Received date: Revised date: Accepted date:
30-11-2015 1-5-2016 25-5-2016
Please cite this article as: Abbas Teimouri, Shima Ghanavati nasab, Niaz Vahdatpoor, Saeed Habibollahi, Hossein Salavati, Alireza Najafi Chermahini, Chitosan/Zeolite Y/Nano ZrO2 nanocomposite as an adsorbent for the removal of nitrate from the aqueous solution, International Journal of Biological Macromolecules http://dx.doi.org/10.1016/j.ijbiomac.2016.05.089 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
1
Highlights
Removal of nitrate ions (NO3-) by CTS/ZY/Nano ZrO2 nanocomposite as adsorbent was
investigated.
Adsorbent was characterized by N2 sorption (BET), FTIR, SEM and XRD.
Effect of molar ratio, pH, temperature on adsorbent capacity and model of kinetics
and isotherm was investigated.
2
Chitosan/Zeolite Y/Nano ZrO2 nanocomposite as an adsorbent for the removal of nitrate from the aqueous solution Abbas Teimouria,*, Shima Ghanavati nasaba,b, Niaz Vahdatpoora, Saeed Habibollahia, Hossein Salavatia, Alireza Najafi Chermahinic a
Chemistry Department, Payame Noor University, 19395-3697, Tehran, I. R. of Iran Department of Chemistry, Shahrekord University, Shahrekord 115, I. R. of Iran c Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111, I. R. of Iran b
Abstract In the present study, a series of chitosan/Zeolite Y/Nano Zirconium oxide (CTS/ZY/Nano ZrO2) nanocomposites were made by controlling the molar ratio of chitosan (CTS) to Zeolite Y/Nano Zirconium oxide in order to remove nitrate (NO3-) ions in the aqueous solution. The nanocomposite adsorbents were characterized by XRD, FTIR, BET, SEM and TEM. The influence of different molar ratios of CTS to ZY/Nano ZrO2, the initial pH value of the nitrate solution, contact time, temperature, the initial concentration of nitrate and adsorbent dose was studied. The adsorption isotherms and kinetics were also analyzed. It was attempted to describe the sorption processes by the Langmuir equation and the theoretical adsorption capacity (Q0) was found to be 23.58 mg nitrate per g of the adsorbent. The optimal conditions for nitrate removal were found to be: molar ratio of CTS/ZY/Nano ZrO2: 5:1; pH: 3; 0.02 g of adsorbent and temperature: 35 ◦C, for 60 min. The adsorption capacities of CTS, ZY, Nano ZrO2, CTS/Nano ZrO2, CTS/ZY and CTS/ZY/Nano ZrO2 nanocomposites for nitrate removal were compared, showing that the adsorption ability of CTS/ZY/Nano ZrO2 nanocomposite was higher than the average values of those of CTS (1.95 mg/g for nitrate removal), ZY, Nano ZrO2, CTS/Nano ZrO2, and CTS/ZY. Keywords: Chitosan, Zeolite Y, Nano ZrO2, Adsorbent, Nanocomposite, Removal, Nitrate.
1. Introduction In recent years, contamination of nitrate in ground water has become a serious concern globally. Nitrates are used in agriculture because of their good solubility in water and their *
Corresponding author at: Department of Chemistry, Payame Noor University (PNU), Isfahan, P.O. Box 81395-671, Iran. Tel.: +98 31 33521804; fax: +98 31 33521802. E-mail addresses: [email protected], [email protected] (A. Teimouri).
3
nutrient value for plants [1, 2]. The nitrate contamination of water is largely due to great amounts of fertilizers, but human and animal wastes, disposal of untreated sanitary and industrial wastes in an unsafe manner, leakage from septic systems, landfill leachate, animal manure and NO x air stripping waste from air pollution control devices are also other important factors. Ground water has largely been used as a source of drinking water. A high nitrate level in water can lead to a risk for humans, e.g. blue baby syndrome for infants [3, 5]. Especially, nitrate can cause serious health problems including eutrophication and infection diseases, such as cyanosis and cancer of the alimentary canal. When nitrogen from ammonia or other sources is combined with oxygenated water, nitrate is generated [6]. Thereupon, nitrate removal from water is of considerable importance from environment and health points of view [7]. Commonly used methods for nitrate removal from water include different processes [8-10] such as biological denitrification, chemical reduction, reverse osmosis and adsorption. Most of the methods are not effective enough and many attempts have been made to find a nitrate removal method that would be both cost effective and easy to perform. For example, maintaining the biological processes at their optimum conditions is bothersome, and the problems of contamination by dead bacteria have to be solved to make such processes desirable for the safe use in water treatment [11]. Also, current available technologies for nitrate removal are expensive and incompetent, generating additional by-products. However, these traditional technologies do not solve the problem related to the additional nitrate in the environment [12, 13]. For nitrate removal, adsorption has become one of the most economic and efficient methods. The process is superior to many other methods of water reuse due to its low initial cost, low energy requirements, ease of design and the possibility of reusing the adsorbent via regeneration. So, this process has received considerable attention during recent years [14]. Various adsorbents have been tested for nitrate removal from
4
water [15-26]. Usually, nitrate removal by different adsorbents has been employed using micronsized particles, but, over the last few years, nanotechnology has become one of the attractive technologies for water treatment. The advantages of using nano-materials may be derived from their self-assembly, large surface area and enhanced reactivity [27] and so, they can be potentially used for water remediation [28, 29]. It is essential that a novel and economical adsorbent for the treatment of nitrate ions in water be developed. Biosorption has been identified as an efficient procedure because of its low cost and good biocompatibility. Chitosan, a linear copolymer of glucosamine and N-acetyl glucosamine, is easily obtained by thermo-chemical deacetylation of crustacean chitin and is regarded as a superb natural adsorbent due to its amine (–NH2) and hydroxyl (–OH) groups; it may also serve as a coordination site to form complexes with various ions [27]. Natural zeolites, which are hydrated aluminosilicate minerals of a porous structure with invaluable physicochemical features, have also been tested for the removal of water pollutants. The chitosan coated zeolite (Ch-Z) is protonated with either sulfuric or hydrochloric acid and tested for its suitability to capture NO3− from water at 20 and 4 ◦C [31]. Zirconium based adsorbents have been given more attention in recent investigations due to excellent anion adsorption capacities. Zirconia (ZrO2) is an inert inorganic metal oxide material. Its chemical inertness and physical strength can enhance the properties of chitosan when fabricating a composite of ZrO2/chitosan is the goal [32]. Various other methods have been used for removing nitrate anions from water Zr(IV) loaded cross-linked chitosan beads [33], Zr(IV)/sugar beet pulp composite [34], activated carbon and Fe2O3 nanoparticles [35], nanoscale zero valent iron supported on pillared clay [36], polypyrrole nanocomposite [37] and SiO2– FeOOH–Fe nanocomposites [38].
5
In this work, for the first time, we synthesized the CTS/ZY/Nano ZrO2 nanocomposite adsorbent for nitrate removal. We report the preparation, characterization and nitrate adsorption ability of CTS/ZY/Nano ZrO2 as well as the related adsorption isotherms and kinetics. Also, the effects of different experimental conditions, such as different molar ratios of CTS to ZY/Nano ZrO2, the initial pH value of the nitrate solution, adsorbent dose, contact time and adsorption temperature, were investigated. As shown in Scheme 1, the sorption mechanism between the adsorbent and nitrate ions occurs in some positions. Scheme 1.
2. Materials and methods 2.1. Materials Chitosan with 85% deacetylated and medium molecular weight was purchased from Sigma-Aldrich. Zeolite Y was purchased from Zeolyst International Co., Brazil. Zirconium oxide nano powder was obtained from Chinese Changsha Zhonglong Chemical (Group) Co. Ltd, in China. All other chemicals were all of the analytical grade.
2.2. Preparation of CTS/ZY/Nano ZrO2 nanocomposite The Chitosan/Zeolite Y/Nano ZrO2 nanocomposite was prepared by a procedure proposed by Wang et al [33]. 2% ( ) using CTS solution (containing CTS amounts of 0.0660, 0.132, 0.660, 3.30 and 6.60 g) and prepared by adding CTS in 1% ( ) and acetic acid solution. The CTS solution was then added to ZY/Nano ZrO2 (the amount of ZY was twice that of Nano ZrO2) mixture suspension to obtain the nanocomposites and heated at 50 ◦C for 5 h. The molar ratios of CTS to ZY/Nano ZrO2 in the samples were varied by using ratios of 1:10, 1:5, 1:1, 5:1
6
and 10:1, respectively, to obtain the series of nanocomposites. After 1 h, 25% ( ), glutaraldehyde was added to the mixture in a 1:40 volume ratio and stirred for another 1 h at 60 ◦C. The neutralization could be made by adding distilled water and the unreacted glutaraldehyde was removed. The products were then dried in the oven at 60 ◦C for 12 h; then it was powdered.
2.3. Adsorption studies For all batch adsorption experiments, a thermostated shaker was applied. The sample was simulated from nitrate-contaminated water (Nitrate: 20 mg/L, Chloride: 7 mg/L, Sulphate: 13.92 mg/L, Nitrite: 0.16 mg/L, Phosphate: 0.34 mg/L, Ammonium: 0.19 mg/L, Calcium: 50.1 mg/L, Magnesium: 6.08 mg/L, Sodium: 2.3 mg/L, Potassium: 0.39 mg/L) of Langan Fountain, Freydan city, Isfahan, Iran. The effect of the molar ratios of CTS to ZY/Nano ZrO2 on nitrate removal was examined by soaking 0.02 g of the adsorbent in 25 mL of nitrate solutions (20 mg/L, the initial pH of 7) at 35 ◦C for 60 min, respectively. The effect of pH on nitrate removal was calculated by immersing 0.02 g of the adsorbent in 25 mL of 20 mg/L nitrate solutions at 30 ◦C for 60 min in various pH values (2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 and 9.0). The influence of temperature on nitrate removal was studied by immersing 0.02 g of the adsorbent in 25 mL of solutions (20 mg/L, pH 3.0) at different temptatures (10-60 ◦C). The effect of the adsorbent dose on nitrate removal was also studied in 25 mL of solution (20 mg/L, pH 3.0) at 35 ◦C for 60 min, in adsorbent doses (0.005, 0.01, 0.02, 0.03, 0.04). The kinetics of nitrate adsorption onto the synthesized nanocomposite was completed by adding 0.02 g of the adsorbent to 25 mL of nitrate solutions (20 mg/L, pH 3.0) at 35 ◦C. Also, for reviewing the isotherm, 20 mg/L nitrate of solution (25 mL, pH 3.0) was shaken with 0.02 g of the adsorbent at 35 ◦C for 60 min.
7
The capacity of the adsorbed nitrate (mg/g) was calculated as stated in the following equation (1): (
)
(1)
, where Co and Ce are the initial and equilibrium concentrations of the adsorbate (mg/L), respectively. Also, m is the mass of the adsorbent (g) and V is the volume of the solution (L). The concentration of nitrate solutions was measured by a UV-Vis spectrophotometer (HACH DR5000, USA), using the standard methods provided by HACH.
2.4. Characterizations The samples were evaluated by X-ray diffraction (XRD) using a Philips X'PERT MPD X-ray diffractometer (XRD) with Cu Kα (1.5405 Aº). Data sets were arranged over the range of 5º– 90º, with a step size of 0.02º, and a count rate of 3.0º/min. The morphology of the samples was evaluated using a SEM (JSM-6300, Tokyo, Japan) and (Seron Technology AIS 2100, South Korea) Transmission electron microscopy (TEM) images were achieved using a Philips-EM2085 transmission electron microscope with an accelerating voltage of 120.0 kV. IR spectra were recorded on JASCO FT/IR-680 PLUS spectrometer. The BET specific surface areas and BJH pore size distribution of the nanocomposites were evaluated using a Series BEL SORP 18.
2.5. Statistical analysis The collected data representing the percentages of the nitrate removal were analyzed through one-way analysis of variance (ANOVA) using SPSS software. Significant differences between treatments were evaluated using the Tukey HSD test. The level of significance was determined based on a probability of p < 0.05.
8
3. Results and discussion 3.1. FT-IR analysis FT-IR spectra of ZY, CTS, and five nanocomposites with various molar ratios of CTS to ZY are shown in Fig. 1. In the spectrum of pure ZY, as shown in Fig. 1g, the band at 1018 cm -1 was attributed to the stretching vibrations of the Y zeolite structure framework and the band at 3448 cm-1 corresponded to the Si–OH group on the surface of zeolite framework. Also, the band at 1620.88 cm-1 was assigned to the bending vibration of H-O-H bond. The FT-IR spectra of the CTS, as shown in Fig. 1a, illustrated the typical band at 3385 cm-1, which was attributed to the stretching vibrations of the OH and N-H bonds. Also, the band at 1654 cm−1 corresponded to the N-H bond of the acetyl group while the band at 1081 cm−1 - was attributed to C-O-C bond. As can be seen in Fig. 1, the intensity of the bands attached to the CTS (amide I (1654 cm−1) and C-O-C bond (1081 cm−1) in the spectra of the nanocomposites was increased with the corresponding increase in the molar ratio of CTS to ZY/Nano ZrO2. In addition, the band at 2924.53 cm−1, 1620.88 cm-1, and 1018.23 cm-1 became stronger with increasing the molar ratios of ZY. Also, the IR spectra of ZrO2 had a significant band at 542 cm−1 which corresponded to the vibration of the Zr-O bond. This band, which could be seen in the FT-IR spectra of the nanocomposites, was increased with the corresponding increase in the molar ratio of ZY/Nano ZrO2 to CTS [32]. In Fig. 2, the FT-IR spectrum of CTS/ZY/ZrO2 nanocomposite before and after adsorption NO3- has been provided. The band at 1376 cm−1 corresponding to the N–O is related to nitrate adsorption. ●Position for Figure 1.
9
●Position for Figure 2.
3.2. XRD analysis X-ray diffraction (XRD) patterns of the adsorbents were evaluated using Cu Kα radiation (λ=1.5405 Aº). The crystallite size of the crystalline phase was determined by using Scherrer formula [39], with a shape factor (K) of 0.9. It could be defined as: Crystallite size=K.λ/W.cosθ, where W=Wb−Ws, while Wb was the broadened profile width of the experimental sample and Ws was the standard profile width of the reference silicon sample [40]. As shown in Fig 3A, pure ZY typically displayed diffraction peaks at 6.40, 10.20, 23.70, 26.50 and 29.50º, whereas, for CTS, the maximum was seen at 19º. In the XRD of ZrO2, the sharp lines at 30.40, 51.00 and 60.2º were attributed to its tetragonal phase. However, in Fig 3B, a pattern could be detected from the bottom to the top, showing a gradual increase of the ZY peak at 23.70 and 26.50 º as the amount used was increased. It could be, therefore, inferred that the formation of the flocculated structure in nanocomposites was due to the hydroxylated edge– edge interaction of the silicate layers. Also, the reduction in the intensity of the peak with increasing the molar ratios of CTS to ZY/ZrO2 confirmed the formation of an intercalated– exfoliated structure in CTS/ZY/ZrO2 nanocomposites. Accordingly, when CTS was intercalated into ZY interlayer, it ruined the crystalline structure of ZY [46]. Also, as shown in Fig 4, XRD patterns of nanocomposites before and after the adsorption of nitrate were compared. It seemed that the nanocomposite had an amorphous structure before adsorption, but, after the adsorption of nitrate, the presence of sharp peaks indicated the formation of a large crystalline material with a more regular structure.
10
● Position for Figure 3. ● Position for Figure 4.
3.3. SEM analysis Fig. 5 illustrates the SEM images of CTS (a), ZY (b), Nano ZrO2 (c), and CTS/ZY/Nano ZrO2 nanocomposite before (d) and after adsorption (e). Chitosan, due to its wide surface, acted as a bed/support for ZY and Nano ZrO2. From fig. 3d, it could be seen that ZY and Nano ZrO2 were scattered on the surface of CTS. The SEM images indicated that the synthesis of the adsorbent was prospering, confirming both the FT-IR and XRD analysis results. Fig. 5 also shows the SEM images of the sample before and after nitrate adsorption. Compared with the nanocomposite before sorption (Fig. 5d), the nitrate-sorbed nanocomposite (Fig. 5e) had a less porous structure and grooves. ● Position for Figure 5.
3.4. TEM Analysis The morphology of the prepared CTS/ZY/Nano ZrO2 nanocomposite was obtained using TEM images (Fig. 6a and b). It was clear that the nanocomposite exhibited agglomerative morphologies with an irregular shape. Despite partial agglomeration, the size of the agglomerated particles was less than 100 nm. ● Position for Figure 6.
3.5. BET Analysis
11
The nitrogen adsorption/desorption isotherm and the pore size distribution (inset) are shown in Fig. 7. Also, table 1 displays the BET surface area values of the CTS, ZY/Nano ZrO2 and CTS/ZY/Nano ZrO2 nanocomposite. The BET surface area, the average pore diameter, and pore volume were 54.619 m2g-1, 0.949 nm and 0.61 cm3 g−1, respectively. The surface area of the sample was greater than that of CTS, most likely due to the fact that the particles of ZY and Nano ZrO2, which had high surface area, were scattered on the CTS bed, enlarging its surface. Consequently, since the average pore diameter of the nanocomposite was larger than that of nitrate ions, which was 0.396 nm, the anions were able to enter the pores easily. The nanocomposite was also mesoporous with N2 adsorption–desorption isotherms of type IV and an H3 hysteresis loop, according to IUPAC classification. The Type H3 loop, which does not show any limiting adsorption at high p/p°, is usually seen with the aggregates of plate-like particles, giving rise to slit-shaped pores [42]. ● Position for Table 1. ● Position for Figure 7. 3.6. Analysis of nitrate in water Concentration of nitrate in all samples was determined by UV–Visible spectrophotometer (HACH DR5000, USA). NitraVer 3 and NitriVer 6 Hach reagents were added to the solution samples. In the presence of nitrate, the solution formed a pink colour which was measured at the wavelength λ=507 nm. For the determination of the nitrate concentration in solution, a calibration curve was prepared with nitrate solutions of known concentrations.
3.6.1.The effect of molar ratios of CTS to ZY/Nano ZrO2 of nanocomposites on adsorption Fig. 8 illustrates the influence of the molar ratios of CTS to ZY/Nano ZrO2 on the nitrate adsorption capacity of the nanocomposites. As can be seen, the nitrate adsorption capacities were
12
rapidly increased with increasing the molar ratio of CTS to ZY/Nano ZrO2 from 1:10 to 5:1; after that, it was reduced again at 10:1. Also, the adsorption capacity of CTS/ZY/Nano ZrO2 nanocomposite (5:1) was seen to be higher than that of CTS/ZY, CTS/Nano ZrO2, ZY, Nano ZrO2 and CTS. So, the optimum molar ratio was 5:1. It was also observed that the composite adsorbent showed some enhanced removal for the nitrate ions as compared to other components. The affinity of adsorbents for the nitrate ions followed the trend: CTS/ZY/Nano ZrO2>CTS/ZrO2>CTS/ZY>ZrO2>CTS>ZY, indicating that the combination of the components provided a great synergistic effect that led to the enhanced removal of the nitrate ions from aqueous solutions. As can be seen in Scheme 1, the composition of chitosan, zeolite and zirconium oxide eliminated nitrate ions througth hydrogen bond formation and electrostatic interactions from aqueous solutions. Chitosan also plays an important role in the removal of nitrate. The adsorption by chitosan could be attributed mainly to their surface, which contained functional groups such as hydroxyl and amino groups. Such chemical groups are the main factor responsible for adsorption anions (by electrostatic attraction). This shows that at acidic pH, the surface of the chitosan was predominated by positive charges (NH2 to NH3+); thus, the surface had a high positive charge density; uptake of negatively charged nitrate ions would be high. On the other hand, zeolite Y with a Faujasite structure could not have a suitable adsorbent for anions, but, with the adsorption of organic materials, it would become a better adsorbent. The link between nitrate ions and OH2+ zeolite can be expected. It is notable that chitosan zirconium oxide composite can adsorb nitrate anions; however, since zeolite can react with nitrate ion and therefore, the rate of nitrate elimination is increased with the addition of zeolite to composite.
13
● Position for Figure 8.
3.6.2. The effect of pH value on adsorption Another considerable factor affecting the adsorption capacity is the pH of the analyte solutions. The influence of the pH value of the sample solution on the nitrate adsorption capacity is shown in Fig. 9. It can be obviously seen that when the pH value of the nitrate solution was increased from 2 to 3, the removal percent was also increased from 37.00 to 42.50%. After that, from 3 to 9, the removal percentage was decreased to around 10% for CTS/ZY/Nano ZrO2 nanocomposite. One possible method for the adsorption of nitarte may be the electrostatic interaction between the NH3+ groups of CTS and the nitrate anion (they formed the ion pair). So, an acidic pH value is needed to provide –NH3+ groups in the CTS structure, thereby helping the enhancement of nitrate adsorption. At a pH value above 7, the hydroxyl ions may compete with the nitrate anions, resulting in a gradual decrease in nitrate uptake, as shown above. On the other side, the pHzpc of adsorbent was determined at 4. As expected, at pH above 4, the adsorbent surface becomes negatively charged, reducing the attraction of the nitrate anions and electrostatic interaction on the negative surface of the adsorbent. At a pH below 4, the adsorbent surface becomes positively charged, intensifying the electrostatic interaction. ● Position for Figure 9.
3.6.3. The effect of temperature on adsorption The relation between the temperature and the percentage removal of the adsorbent is shown in Fig. 10. The percentage removal of the adsorbent was increased from 35 to 40 with
14
increasing the temperature from 10 to 35 ◦C; after that, it was reduced strongly from 40 to 50 ◦C. So, 35 ◦C was selected as the optimum temperature. ● Position for Figure 10.
3.6.4. The effect of the adsorbent dose on adsorption The influence of the adsorbent dose on nitrate removal at the nitrate concentration of 20 mg/L, pH of 3 and the temperature of 35 ◦C is illustrated in Fig. 11. It was shown that the removal percentage of nitrate was increased from 22.5% to 40% with the increase in the adsorbent dose from 0.005 to 0.02 g/25 mL, respectively. It was also seen that after a dose of 0.02 g, there was a sharp decline in the percentage removal. In fact, with increasing the amount of the adsorbent, accumulation of adsorbent particles on each other could reduce the rate of removal. Therefore, the optimum dose was chosen to be 0.02 g/25.00 mL. ● Position for Figure 11.
3.6.5. Adsorption kinetics The effect of contact time on the removal percentage of nitrate by the CTS/ZY/Nano ZrO2 nanocomposite was investigated. It turned out that the adsorption equilibrium of nitrate on the nanocomposite was accomplished in 60 min. So, for the test, an adsorption time of 60 min was chosen for the adsorption isotherms to ensure that the adsorption equilibrium was achieved. Two simplified kinetic models, including pseudo-first-order and pseudo-second-order equations, were checked out. The rate constant of adsorption can be defined using the pseudo-first-order equation given by Langergren [43]: (
)
(2)
15
,where k1 is the pseudo-first-order rate constant (min−1), and qe and qt are the amounts of nitrate adsorbed (mg/g) at equilibrium and at time t (min). The pseudo-second-order equation, based on equilibrium adsorption, can be defined as [44]: (3) ,where k2 (g mg−1 min−1) is the rate constant of the pseudo-second-order adsorption. In Fig. 12, the linear plots of log (qe−qt) versus t and (t/qt) versus t are shown for pseudo-first-order and pseudo-second-order models, respectively. The rate constants k1 and k2 could be calculated from the plot of the experimental data. The correlation coefficients R2 of the pseudo first-order model was 0.9385 and for the pseudo-second-order model, it was 0.9950 (see Table 2). This showed that the adsorption of nitrate on adsorbent could be better defined by the pseudo-secondorder, rather than the pseudo-first-order. This also revealed that the adsorption of nitrate onto the nanocomposite was controlled by chemical adsorption. In chemical adsorption, It is supposed that the adsorption capacity is proportional to the number of active sites occupied on the nanocomposite surface [45]. ● Position for Figure 12. ● Position for Table 2.
3.6.6. Adsorption isotherms The adsorption capacity of nitrate by adsorbent was investigated at different nitrate concentrations and at 35 ◦C for samples. The results illustrated a strong rise in adsorption capacity as the nitrate concentration was increased from 5 to 200 mg/L for the nanocomposite. It was found that the nitrate adsorption capacity of the adsorbent was increased by enhancing the
16
nitrate concentration. But, increasing the initial concentration of nitrate beyond 80 mg/L led to a gradual growth in the adsorption capacity of the adsorbent. The adsorption process is commonly explained by two isotherm equations, namely, the Langmuir and the Freundlich equations [40], which are brought below, respectively: (4) ⁄
(5)
,where qm (mg/g) and b (L/mg) are Langmuir isotherm coefficients and qm indicates the maximum adsorption capacity. Kf (mg/g) and n are also the Freundlich constants representing adsorption capacity and adsorption intensity, respectively. The Langmuir and Freundlich adsorption isotherm for CTS/ZY/ZrO2 nanocomposite is shown in Fig. 13. The Langmuir isotherm accounted for the monolayer cover of the nitrate on the surface of nanocomposite and the values of R2 and qm for the nanocomposite were 0.993 and 23.58, respectively. On the other hand, the value of R2 in Freundlich model for the nanocomposite was 0.8347. Therefore, the adsorption of nitrate on nanocomposite did not fit the Freundlich isotherm (see Table 3). In addition, a comparison of adsorption capacity (mg/g) and other experimental conditions of some different sorbents for nitrate removal is shown in Table 4. One of the substantial preferences of adsorbents in operation is the possibility of reuse, without any notable loss in the sorption ability. The adsorbents were used in 4 runs and after each run, they were separated by filtration and washed twice with 5 ml NaOH (NaOH was used as the desorption agent because it helped the release of nitrate ions bonded to the amino groups on CTS chains, thereby allowing them to return to the initial state. It was washed with deionised water severally and dried in an oven at 80 ºC for about 5 h. The recovered adsorbent could then be reused in the next run. A comparison of the removal percentage in four sequential runs
17
(31.9%, 25.8%, 24.7% and 17.7%) showed that the adsorbent could be reused several times without any considerable loss of its sorption ability.
● Position for Figure 13. ● Position for Table 3. ● Position for Table 4.
4. Conclusions In this research, a novel low-cost biosorbent, chitosan/Zeolite Y/Nano ZrO2 nanocomposite material, was prepared using environmentally friendly and cheap chitosan, zeolite and zirconium oxide. The results showed that it could effectively eliminate nitrate under acidic conditions via the chelation between No3− and the amine group of complex. It was also found that the nitrate adsorption process was dependent on the molar ratios of CTS to ZY/Nano ZrO2, the initial pH value of the nitrate solution and temperature. By controlling these parameters, optimal conditions for nitrate adsorption were obtained. The adsorption kinetics were seen to obey the pseudo-second-order model, and the isotherm followed the Langmuir monolayer model. Compared with CTS, ZY, Nano ZrO2, CTS/Nano ZrO2 and CTS/ZY, the CTS/ZY/Nano
ZrO2 nanocomposite
had
higher
adsorption
capacity.
Therefore,
nanocomposite could be efficiently used as an adsorbent for the elimination of nitrate.
Acknowledgements
the
18
We gratefully acknowledge the financial assistance provided by the Payame Noor University in Isfahan Research council (Grant # 62370). We also appreciate Isfahan University of Technology. The authors would like to thank Dr. H. Jalali for correcting language problems.
References [1] J.F. Power, J.S. Schepers, Agric. Ecosyst. Environ. 26 (1989) 165–187. [2] E.V.S.P. Rao and K. Puttanna, Curr. Sci. 79 (2000) 1163-1168. [3] M. Islam and R. Patel, Desalination 256 (2012) 120-128. [4] L. Knobeloch, B. Salna, A. Hogan, J. Postle, H. Anderson, Environ. Health Perspect. 108 (2000) 675–678. [5] D.S. Powlson, T.M. Addiscott, N. Benjamin, K.G. Cassman, T.M. de Kok, H. van Grinsven, J. L. L Hirondel, A.A. Avery, C. van Kessel, J. Environ. Qual. 37 (2008) 291–295. [6] I.D. Patil, M. Husain, V.R.Rahane, Int. J. Mod. Eng. Res. 3 (2013) 346-349. [7] A. Elmidaoui , F. Elhannouni, M.A. Menkouchi Sahli, L.Chay, E. Elabbassi, M. Hafsi, D. Largeteau, Desalination 136 (2001) 325–332. [8] J.B.K. Park and R.J. Craggs, Bioresour. Technol. 100 (2009) 3175-3179. [9] J.F. Li, Y.M. Li, and Q.L. Meng, J. Hazard. Mater. 174 (2010) 188-193. [10] J.J. Schoeman and A. Steyn, Desalination 155 (2003) 15-26. [11] M. Chabani, A. Amraneb, A. Bensmaili, Chem. Eng. J. 125 (2006) 111–117. [12] M.I.M. Soares, Water Air Soil Pollut. 123 (2000) 183–193. [13] C.D. Rocca, V. Belgiorno, S. Meric., Desalination 204 (2007) 46–62. [14] C. Namasivayam, K. Kadirvelu, Biores Tech 21 (2001) 381-387. [15] Y. Cengeloglu, A. Tor, M. Ersoz, G. Arslan, Sep. Purif. Technol. 51 (2006) 374–378.
19
[16] A. Bhatnagar, M. Ji, Y.-H. Choi, W. Jung, S.-H. Lee, S.-J. Kim, G. Lee, H. Suk, H.-S. Kim, B. Min, S.-H. Kim, B.-H. Jeon, J.W. Kang, Sep. Sci. Technol. 43 (2008) 886–907. [17] K. Mizuta, T. Matsumoto, Y. Hatate, K. Nishihara, T. Nakanishi, Bioresour. Technol. 95 (2004) 255–257. [18] N. Öztürk, T.E. Bektas, J. Hazard. Mater. B112 (2004) 155–162. [19] Y. Xi, M. Mallavarapu, R. Naidu, Appl. Clay Sci. 48 (2010) 92–96. [20] K. Hosni, E. Srasra, Inorg. Mater. 44 (2008) 742–749. [21] M.M. Socías-Viciana, M.D. Urena-Amate, E. González-Pradas, M.J. García- Cortés, C. López-Teruel, Clay Clay Miner. 56 (2008) 2–9. [22] M. Islam, R. Patel, J. Hazard. Mater. 169 (2009) 524–531. [23] M. Islam, P.C. Mishra, R. Patel, J. Environ. Manage. 91 (2010) 1883–1891. [24] Zh. Feng, W. Wei, L. Wang, R. Hong, RSC Adv. 5 (2015) 96911-96917. [25] Ying Li, Xiaoyan Lin, Xiurong Zhuo, Xueguang Luo, J. Appl. Polym. Sci. 128 (2013) 2746–2752. [26] A. Sowmya, S. Meenakshi, Int. J. Biol. Macro- mol. 64 (2014) 224-232. [27] K. Hristovski, A. Baumgardner, P. Westerhoff, J. Hazard. Mater., 147 (2007) 265–274. [28] X. Zhao, J. Wang, F. Wu, T.Wang, Y. Cai, Y. Shi, G. Jiang, J. Hazard. Mater., 173 (2010) 102–109. [29] A. Bhatnagar, E. Kumar, M. Sillanpää, Chem. Eng. J. 163 (2010) 317–323. [30] A. Teimouri, Sh. Ghanavati Nasab, S. Habibollahi, M. Fazel-Najafabadi and A. Najafi Chermahini, RSC Adv. 5 (2015) 6771- 6781. [31] M. Arora, N.K. Eddy, K.A. Mumford, Y. Baba, J.M. Perera, G.W. Stevens, Cold Regions Sci. Technol. 62 (2010) 92–97.
20
[32] H. Jiang, P. Chen, Sh. Luo, Xinman Tu, Q. Cao, M. Shu, J. Appl. Polym. Sci. 284 (2013) 942–949. [33] A. Sowmya, S. Meenakshi, Int. J. Biol. Macro- mol. 69 (2014) 336-343. [34] M. L. Hassan, N. F. Kassem, A. H. Abd El-Kader, J. Appl. Polym. Sci. 117 (2010) 2205– 2212. [35] N. Mehrabi, M. Soleimani, M. Madadi Yeganeh, H. Sharififard, RSC Adv.5 (2015) 5147051482. [36] Y. Zhang, Y. Li, J. Li, L. Hu, X. Zheng, Chem. Eng. J. 171 (2011) 526– 531. [37] H. Pahlavanzadeh, R. Katal, H. Mohammadi, J. Ind. Eng. Chem.18 (2012) 948–956 [38] E. Bekhradinassab, S. Sabbaghi, Desalination 347 (2014) 1–9. [39] S. L. Sun and A. Q. Wang, J. Hazard. Mater. 131 (2006) 103–111. [40] K. Periasamy and C. Namasivayam, Waste Manage. 15 (1995) 63–68. [41] H. L. Liu, X. F. Sun, C. Q. Yin and C. Hu, J. Hazard. Mater. 151 (2008) 616–622. [42] K. S. W. Sing, D. H. Everett, R. A. W. Haul, L. Moscou, R. A. Pierott, J. Rouquerol, T. Siemieniewska, Pure & Appl. Chem. 57 (1985) 603-619. [43] S. Lagergren. Kungliga Svenska Vetenskapsakademiens Handlingar 24 (1898) 1–39. [44] Y.S. Ho, G. McKay. Process Biochem. 34 (1999) 451–465. [45] A. Özer, G. Dursun, J. Hazard. Mater. 146 (2007) 262–269. [46] Q. Hu, N. Chen, Ch. Feng, W. Hu, Appl. Surf. Sci. 347 (2015) 1–9. [47] Y. Xi, M. Mallavarapu, R. Naidu, Appl. Clay Sci. 48 (2010) 92–96. [48] A. Bhatnagar, M. Ji, Y.-H. Choi, W. Jung, S.-H. Lee, S.-J. Kim, G. Lee, H. Suk, H.-S. Kim, B. Min, S.-H. Kim, B.-H. Jeon, J.-W. Kang, Sep. Sci. Technol. 43 (2008) 886–907.
21
[49] K. Mizuta, T. Matsumoto, Y. Hatate, K. Nishihara, T. Nakanishi, Bioresour. Technol. 95 (2004) 255–257. [50] P.C. Mishra, R.K. Patel, J. Environ. Manag. 90 (2009) 519–522. [51] A. Rezaee, H. Godini, S. Dehestani, A. Khavanin, Iran. J. Environ. Health Sci. Eng. 5 (2008) 125–130. [52] M.F.A. Taleb, G.A. Mahmoud, S.M. Elsigeny, E.S.A Hegazy, J. Hazard. Mater. 159 (2008) 372–379. [53] S. Chatterjee, S.H. Woo, J. Hazard. Mater. 164 (2009) 1012–1018. [54] M.L. Hassan, N.F. Kassem, A.H.A. El-Kader, J. Appl. Polym. Sci. 117 (2010) 2205–2212. [55] H. Demiral, G. Gündüzog˘lu, Bioresour. Technol. 101 (2010) 1675–1680. [56] A. Bhatnagara, E. Kumarb, M. Sillanpääc, Chem. Eng. J. 163 (2010) 317–323. [57] S. Chatterjee, D. S. Lee, M. W. Lee, S. H.Woo, J. Hazard. Mater. 166 (2009) 508–513. [58] R. Saad, Kh. Belkacemi, S. Hamoudi, J. Coll. Int. Sci. 311 (2007) 375–381. [59] R. Saad, S. Hamoudi, Kh. Belkacemi, J Porous Mater. (2008) 15 315–323.
22
Scheme 1. Proposed sorption mechanism between the adsorbent and nitrate ions. Fig. 1. FTIR spectra of a) CTS; the nanocomposites with the molar ratios CTS to ZY/Nano ZrO 2; b) 10:1; c) 5:1; d) 1:1; e) 1:5; f) 1:10; and g) ZY. Fig. 2. FTIR spectra of a) CTS/ZY/Nano ZrO2 nanocomposite before adsorption and b) after nitrate adsorption. Fig. 3. (A)- XRD patterns of a) Nano ZrO2; b) ZY; and c) CTS. (B)- XRD patterns of CTS/ZY/Nano ZrO2 nanocomposite with different molar ratios: a) 10:1; b) 5:1; c) 1:1; d) 1:5; and e) 1:10. Fig. 4. XRD patterns of a) CTS/ZY/Nano ZrO2 nanocomposite before adsorption and b) after nitrate adsorption with the molar ratio of 5:1. Fig. 5. SEM images of a) CTS; b) ZY; c) Nano ZrO2; d) nanocomposite before adsorption and e) after nitrate adsorption. Fig. 6. TEM images of the CTS/ZY/Nano ZrO2 scaffolds. Fig. 7. N2 adsorption–desorption isotherm of CTS/ZY/Nano ZrO2. Inset: Pore size distribution using BJH method. Fig. 8. The effect of the molar ratios of CTS to ZY/ZrO2 on the adsorption capacity of the nanocomposites for nitrate. Concentration: 20 mg/L; sample range: 0.02 g/25.00 mL; natural pH; temperature: 30 ◦C; and equilibrium time: 60 min. Fig. 9. The effect of the pH values on the adsorption capacity of CTS/ZY/ZrO 2 nanocomposite for nitrate: nitrate concentration: 20 mg/L; sample range: 0.02 g/25.00 mL; pH range: 2–9; temperature: 30 ◦C; and equilibrium time: 60 min. Fig. 10. The effect of the temperature on the adsorption capacity of the CTS/ZY/Nano ZrO 2 nanocomposite for nitrate. Nitrate concentration: 20 mg/L; sample range: 0.02 g/25.00 mL; pH: 3; temperature: 10–60 ◦C; and equilibrium time: 60 min. Fig. 11. The effect of the adsorbent dose on the percentage removal of nitrate anions at nitrate concentration: 20 mg/L; pH: 3; temperature: 35 ◦C; and equilibrium time: 60 min. Fig. 12. a) Pseudo-first order kinetic and b) Pseudo second order kinetic for nitrate adsorption by CTS/ZY/ZrO 2 nanocomposite (80 mg.L-1 nitrate solution). Fig. 13. a) Langmuir adsorption isotherm and b) Freundlich adsorption isotherm for CTS/ZY/ZrO2 nanocomposite.
23
Table 1 BET surface area values of CTS/ZY/Nano ZrO2. BET surface Pore volume Catalyst area (m2g-1) (cm3 g−1) Chitosan 4 0.10 ZY/Nano ZrO2 CTS/ZY/Nano ZrO2
Average pore diameter (nm) 3.5
92
0.23
4
54.619
0.61
0.949
24
Table 2 Kinetic parameter for the sorption of NO3− anion on to a CTS/ZY/ZrO2 nanocomposite. No3− qe (exp) Pseudo-first-order Pseudo-second-order C0 (mg/g) qe (cal) (mg/g) K1 (1/min) R2 qe (cal) (mg/g) K2 (g/mg min) (mg/L) 80 120 160 200
22.50 25 27 30
34.70 38.12 41.15 47.78
0.000143 0.000148 0.000141 0.000154
0.9385 0.8689 0.8478 0.8248
23.10 28.12 31.15 35.78
0.011833 0.01177 0.01183 0.01180
R2
0.9950 0.9884 0.9950 0.9935
25
Table 3 Values of different isotherm parameters. No3− sorption Langmuir isotherm qm (mg/g) b (L/mg) R2
23.58 0.1557 0.9930
Freundlich isotherm Kf 1/n R2
4.8745 0.3141 0.8347
26
Table 4 A comparative evaluation of adsorption capacity (mg/g) and other experimental conditions of some different adsorbent for nitrate removal. Experimental conditions Amount References Adsorbent adsorbed Zn/Al chloride layered double pH: 6.0 85.4% 3 hydroxide Concentration range: 10 mg/L Temperature: 25 ◦C hydroxyapatite pH: 6.0 21 mg/g 23 Concentration range: 100 mg/L Temperature: 50 ◦C Granular chitosan-Fe3+ complex pH: 5.0 8.35 mg/g 46 Concentration: 50 mg/L Temperature: 25 ◦C Halloysite pH: 5.4 0.54 mg/g 47 Concentration: 100 mg/L Room Temperature ZnCl2 treated coconut granular pH: 5.5 10.2 mg/g 48 activated carbon Concentration range: 5–200 mg/L Temperature: 25 ◦C Untreated coconut granular activated pH: 5.5 1.7 mg/g 48 carbon Concentration range: 5–200 mg/L Temperature: 25 ◦C Bamboo powder charcoal pH: n.a 1.25 mg/g 49 Concentration range: 0-10 mg/L Temperature: 10 ◦C Commercial activated carbon pH: n.a 1.22 mg/g 50 Concentration range: 0-25 mg/L Temperature: 15 ◦C Mustard straw charcoal pH: n.a 1.30 mg/g 50 Concentration range: 0-25 mg/L Temperature: 15 ◦C Impregnated almond shell activated pH: 6.2 16-17 mg/g 51 carbon Concentration range: 10-50 mg/L Temperature: 20 ◦C Polypropylene-g-N,N-dimethylamino pH: n.a 12.5 mg/g 52 ethylemthacrylate) graft copolymer Concentration range: 25–100 mg/L Temperature: 25 ◦C Chitosan hydrogel beads pH: 5.0 90.7 mg/g 53 Concentration range: 25–1000 mg/L Temperature: 30 ◦C Zr(IV)-loaded sugar beet pulp
activated carbon prepared from sugar beet bagasse
nano-alumina
pH: 6.0 Concentration: n.a Temperature: 25 ◦C pH: 3.0 Concentration range: 10–200 mg/L Temperature: 45 ◦C pH: 4.4 Concentration range: 1–100 mg/L Temperature: 25 ◦C
63 mg/g
54
27.55 mg/g
55
4.0 mg/g
56
27
cross-linked chitosan beads conditioned with sodium bisulfate
pH: 5.0 Concentration: 500 mg/L Temperature: 30 ◦C
104.0 mg/g
57
ammonium-functionalized MCM-48
pH < 8, Concentration: 300 mg/L Temperature: 25 ◦C
27.6 mg/g
58
ammonium-functionnalized mesoporous silicas
pH = n.a, Concentration: 130 mg/L Temperature: 25 ◦C
46.5 mg/g
59
CTS/ZY/Nano ZrO2 nanocomposite
pH: 3.0 Concentration: 20 mg/L Temperature: 35 ◦C
23.58 mg/g
Present study
28
Scheme 1. Proposed sorption mechanism between the adsorbent and nitrate ions
Fig. 1. FTIR spectra of a) CTS; the nanocomposites with the molar ratios CTS to ZY/Nano ZrO 2; b) 10:1; c) 5:1; d) 1:1; e) 1:5; f) 1:10; and g) ZY.
29
Fig. 2. FTIR spectra of a) CTS/ZY/Nano ZrO2 nanocomposite before adsorption and b) after nitrate adsorption.
Fig. 3. (A)- XRD patterns of a) Nano ZrO2; b) ZY; and c) CTS. (B)- XRD patterns of CTS/ZY/Nano ZrO2 nanocomposite with different molar ratios: a) 10:1; b) 5:1; c) 1:1; d) 1:5; and e) 1:10.
Fig. 4. XRD patterns of a) CTS/ZY/Nano ZrO2 nanocomposite before adsorption and b) after nitrate adsorption with the molar ratio of 5:1.
30
a
b
c
d
e
Fig. 5. SEM images of a) CTS; b) ZY; c) Nano ZrO2; d) nanocomposite before adsorption and e) after nitrate adsorption.
31
a
b
Fig. 6. TEM images of the CTS/ZY/Nano ZrO2 nano-adsorbent.
Fig. 7. N2 adsorption–desorption isotherm of CTS/ZY/Nano ZrO2. Inset: Pore size distribution using BJH method.
Fig. 8. The effect of the molar ratios of CTS to ZY/ZrO2 on the adsorption capacity of the nanocomposites for nitrate. Concentration: 20 mg/L; sample range: 0.02 g/25.00 mL; natural pH; temperature: 30 ◦C; and equilibrium time: 60 min.
32
Fig. 9. The effect of the pH values on the adsorption capacity of CTS/ZY/ZrO 2 nanocomposite for nitrate: nitrate concentration: 20 mg/L; sample range: 0.02 g/25.00 mL; pH range: 2–9; temperature: 30 ◦C; and equilibrium time: 60 min.
Fig. 10. The effect of the temperature on the adsorption capacity of the CTS/ZY/ZrO 2 nanocomposite for nitrate. Nitrate concentration: 20 mg/L; sample range: 0.02 g/25.00 mL; pH: 3; temperature: 10–60 ◦C; and equilibrium time: 60 min.
Fig. 11. The effect of the adsorbent dose on the percentage removal of nitrate anions at nitrate concentration: 20 mg/L; pH: 3; temperature: 35 ◦C; and equilibrium time: 60 min.
33
a
b Fig. 12. a) Pseudo-first order kinetic and b) Pseudo second order kinetic for nitrate adsorption by CTS/ZY/ZrO 2 nanocomposite (80 mg.L-1 nitrate solution).
34
a
b Fig. 13. a) Langmuir adsorption isotherm and b) Freundlich adsorption isotherm for CTS/ZY/ZrO2 nanocomposite.