Comparison of the efficiency of activated carbon and neutral polymeric adsorbent in removal of chromium complex dye from aqueous solutions

Journal of Hazardous Materials 179 (2010) 933–939

Contents lists available at ScienceDirect

Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat

Comparison of the efficiency of activated carbon and neutral polymeric adsorbent in removal of chromium complex dye from aqueous solutions ˙ D. Kauˇspedien e˙ a,∗ , E. Kazlauskiene˙ a , A. Gefeniene˙ a,b , R. Binkiene˙ a a b

Institute of Chemistry, A. Goˇstauto 9, 01108 Vilnius, Lithuania Vilnius Pedagogical University, Studentu˛ 39, 01108 Vilnius, Lithuania

a r t i c l e

i n f o

Article history: Received 19 November 2009 Received in revised form 22 March 2010 Accepted 23 March 2010 Available online 30 March 2010 Keywords: Chromium complex dye Removal Basic activated carbon Hyper-cross-linked polystyrene Kinetic

a b s t r a c t The removal efficiency of chromium complex dye Lanasyn Navy M-DNL from aqueous solution using the activated carbon (AC) and the neutral polymeric adsorbent Macronet MN 200 (MN 200) has been investigated under various experimental conditions: initial dye concentration, pH and temperature. The effectiveness of MN 200 for the dye removal was found relatively higher than that of AC in both acidic and neutral solutions. Two theoretical models (pseudo-second-order-reaction and intraparticle diffusion) were used to describe the sorption kinetics, and to determine the constants of sorption rate (k2 ), intraparticle (ki ) and film diffusion (ks ). The both sorption systems dye-AC and dye-MN 200 follow the pseudo-second-order model with a higher k2 value for dye-MN 200 in acidic media at 20 ◦ C when compared with that of the dye-AC. With increase in the solution temperature from 20 to 40 ◦ C the k2 value for dye-AC indicate an increase in acidic media and decrease in alkaline media; whereas k2 values for dye-MN 200 decrease in both acidic and neutral media. The rate of dye adsorption on both adsorbents is dependent on intraparticle and film diffusion proceeding simultaneously. The boundary layer effect is more pronounced in acidic solutions and with increase in temperature. © 2010 Elsevier B.V. All rights reserved.

1. Introduction The textile finishing industry, as a major user and potential polluter of water is under particular pressure to reduce water consumption on both environmental and economic grounds. Wastewater from textile industries is highly colored, complex and variable in nature [1–5]. One problematic group of substances, present in mixed wastewater from textile industry that must be removed, is metal complex dyes [6]. Metal complexes can be found in textile finishing wastewater when using acid, direct, and reactive dyes, as well as pigments. Metals used in dyes include mainly chromium, cobalt and copper. Environmental concerns arise from the carcinogenic properties of these metals and from amines formed by reductive cleavage of azo groups [7,8]. Therefore, the removal of metal complex dyes has been targeted as one of the most important issues in textile wastewater treatment. Process water recycling requires a total decolorization and an extensive elimination of all organic and inorganic contents. This can only be realized in multistage technique combinations. For example, adsorption onto activated carbon follows the conventional biological and physico-chemical processes. Water resources man-

∗ Corresponding author at: Institute of chemistry, Ecological chemistry, A. Gostauto 9, Vilnius, Lithuania. Tel.: +370 5 2648843; fax: +370 5 2649774. ˙ ˙ E-mail address: [email protected] (D. Kauˇspedien e). 0304-3894/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2010.03.095

agement has become an important operational and environmental issue in Lithuania. The rising costs of dependable water supplies and wastewater disposal have increased the economic incentive for implementing technologies that are more environmental friendly, and can ensure efficient use of natural resources. Residual color has to be limited for process water recycling, i.e., reuse of reclaimed rinsing water or dye bath [9]. The general regulations in Lithuania do not include a regulation for the presence of color. For discharge of textile wastewater in sewerage, the permitted value of the ratio between the chemical oxygen demand (COD) and the biochemical oxygen demand (BOD7 ) is <3, whereas a maximal COD is of 125 mg/L O2 . The permitted concentration of chromium is 0.4 mg/L [10]. The requirements for reuse of wastewater as process water are less obvious. In the textile industry, the required water quality is generally not determined. A few basic conditions are related to water turbidity, which should be comparable to that of the groundwater, which is used as freshwater. The water hardness should be in the normal range for relatively soft groundwater (not higher than 40 mg/L Ca). Of course, all colors should be removed before reuse. Furthermore, no concentration of other components such as heavy metals can be allowed in the water cycle. The adsorption onto a wide range of natural, organic, synthetic materials, including activated carbon is an effective method for removing dyes from wastewater not only to permitted concentrations of chemical oxygen demand (COD) and color but also for preventing the contamination of envi-

934

D. Kauˇspedien e˙ et al. / Journal of Hazardous Materials 179 (2010) 933–939 ˙

ronment by carcinogenic metals ions and azo compounds [5,11–17]. Adsorption on activated carbon of cationic and anionic dyes, acid and reactive dyes as well as heavy metals ions has been investigated by a number of researchers [12–16]. It is possible to tailor the chemical properties of activated carbons by appropriate thermal and chemical treatments, to enhance their effectiveness. The thermal treatment produces activated carbons with a strong basic character (high basicity and high pHpzc ). In addition to the Brønsted basicity that results from some remaining oxygen-containing surface groups, also the oxygen-free Lewis basic sites on the graphene layers must be considered [17]. Various oxidation agents can introduce a variety of acid functional groups upon oxidizing the surface of carbon. The adsorption capacity of chemically oxidized carbons for heavy metals ions is much higher compared to that of untreated ones [12]. However the presence of acid oxygenated groups on the activated carbon surface is detrimental to the adsorption of acid dyes, not only because of the repulsive forces developed but also because those are electron-withdrawing groups. The adsorption of acid dyes on basic activated carbons is favored, because the positively charged adsorbent surface enhances the adsorption of the anionic dye via electrostatic interactions [13]. In order to be an effective adsorbent for anionic dyes the carbon should have a high pHpzc (>7.0) and be of the H-carbon type [5]. However some disadvantages using activated carbon was observed, e.g., high regeneration costs and production of fines due to the brittle nature [18]. For this reason, many researchers have investigated on the one hand low-cost, locally available substitutes for activated carbon made from natural sources such as clays, zeolite, montmorillonite, smectite, bentonite, sepiolite to remove dyes from wastewater [19]. On the other hand, because their adsorption capacities, mechanical strength, and other properties need further improvement for wider application, the polymeric sorbents are still under development as a potential alternative to activated carbons. Numerous studies are focused on the removal of acid and reactive dyes using different functionalized polymeric adsorbents (strongly and weakly basic anion exchangers) with gel or macroporous structures of styrene–divinylbenzene or acrylic matrices [20–25]. Anion exchange resins Lewatit MP-62 and Lewatit S6328A were used for the removal of textile dyes such as Reactive Red 120, Reactive Red 198, Reactive Black 5 as well as for Reactive Blue 15 (copper complex) [20]; Amberlite IRA-67, Amberlite IRA-402 and Amberlite IRA-958 anion exchangers were applied for the removal of Brilliant Yellow [21]. Purolite A 850 was tested for Acid Blue 29 retention [22], whereas Lewatit MonoPlus M-600—for food dyes such as Allura Red, Tartrazine, Sunset Yellow and Indigo Carmine [23]. Tartrazine was also successfully removed by Amberlite IRA 900 and Amberlite IRA 910 [24]. Amberlyst A-21 and Amberlyst A-29 are capable to adsorb SPADNS [25]. In addition, Amberlite IRA67, saturated with Brilliant Yellow, as a prototype of a chelating ion exchanger, could be applied for Cu(II), Ni(II) and Co(II) ions recovery from wastewater and their trace analysis [21]. Among widely used polymeric adsorbents is a class of neutralto-weakly-polar-macroporous polystyrene resins that are superb adsorbents for organic compounds. Because of their higher physicochemical stabilities and better regeneration properties they have been commercialized as alternatives to activated carbon [26,27]. The macroporous neutral resins such as OC1064, OC1066 (Bayer AG, FR Germany) showed moderate maximum loadings of reactive dyes (100–400 ␮mol/g or 100–400 mg/g), but low affinity and were not suitable for large dyes (>1000 g/mol) [20]. Hyper-cross-linked polymeric adsorbents, including Macronets (Purolite International Ltd.), have both macropores and micropores, the latter providing the high surface area and the former providing rapid access to the internal surfaces. In addition, conventional ion exchange functional groups can be attached to their matrix. The use of Macronets non-

functionalized MN 200 and weak basic MN 300 for the dye (Acid red 14) removal from synthetic solution has been studied [28,29]. Treatment of textile dye house waste streams using Macronets is a new industrial technology in development by Technocom through 5 operating plants in Italy [30]. Because there exists a large variety of dyes and their removal is based on dye–adsorbent interaction that dependent on the number and type of functional groups or the chemical and physical structures of matrix and on the structure of dye, the related performance of adsorbent should be intensively evaluated in the particular case [20,31]. There is very little information in the literature about the removal of metal complex dyes using hyper-cross-linked polystyrene resins. As the total capacity for non-functionalized polymeric adsorbent cannot be readily determined, it is necessary to carry out experimental study under the determined conditions. Therefore in this paper we aimed at investigating the efficiency of hyper-cross-linked neutral polymer Macronet MN 200 in comparison with that of commercial activated carbon for removal of chromium complex dye from aqueous solutions in batch systems. Adsorption and kinetic characteristics for the chromium complex dye–adsorbent system at different temperatures and solution pH were studied. Special attention was given to the variation in removal of hazardous components such as chromium and organic substances (COD).

2. Materials and methods 2.1. Materials Extruded activated carbon Norit RB 0.8 CC (AC) with a total surface area of 1150 m2 , particle size 0.6 mm, supernatant pH 9.42, was supplied by Norit Company (AC Amersfoort, Netherlands). FTIR spectrum of original sample was recorded using Bomem B 100 spectrometer (Hartman & Braun, Canada) within the wave number range of 500–4000 cm−1 . Purolite International Ltd., supplied a Macronet MN 200 sample. It is neutral, hyper-cross-linked polystyrene with a pore volume of 1.1 mL/g, specific gravity of 1.04 g/mL, and total surface area of 1000 m2 /g (obtained from manufacturer). Only a wet fraction of the narrow size range was used (0.5–0.7 mm). The adsorbents were washed with deionized water and then dried at 60 ◦ C for 12 h. The tested chromium complex dye was the commercial textile dye anionic Lanasyn Navy M-DNL obtained from Clariant (Schweiz). Chemically, it is a 1:2 chromium monoazo complex dye (trisodium bis [3-hydroxy-4 [(2-hydroxy-1-naphthyl) azo] naphthalene-1sulfonato (3-)] chromate (3-)) with the molar mass of 834 g/mol. Chemical structure of the dye is presented in Fig. 1.

Fig. 1. Chemical structure of dye Lanasyn Navy M-DNL [8].

D. Kauˇspedien e˙ et al. / Journal of Hazardous Materials 179 (2010) 933–939 ˙

935

Table 1 Effectiveness of AC Norit RB 08.CC and Macronet MN 200 in the removal of color, chromium, COD from aqueous dye solutions. Conditions: adsorbent mass 0.5 g; volume of solution 25 mL; contact time 1 h. Dye solution before treatment C0 (␮mol/L)

Cr (mg/L)

Dye solution treated using AC Norit RB 08.CC COD (mgO2 /L)

4

0.62

73.5

8

1.23

147

20

3.08

367.5

40

6.16

735

80

12.32

1102.5

Dye solution treated using Macronet MN 200

pH

Res (%)

pH

Cr (mg/L)

COD (mgO2 /L)

Res (%)

pH

Cr (mg/L)

COD (mgO2 /L)

2.0 7.0 2.0 7.0 2.0 7.0 2.0 7.0 2.0 7.0

10 40 18 50 28 70 40 80 60 88

1.8 9.7 1.6 10.3 1.5 10.3 1.45 10.3 1.4 10.3

0 0 0 0 0 1.50 1.50 3.58 4.05 7.90

40 70 55 120 77 128 99 135 172 440

2.2 30 2.4 40 3.5 44 3.8 50 4.4 64

1.9 6.9 1.9 6.8 1.9 6.9 1.9 6.9 1.9 6.9

0 0 0 0 0 0.43 0 1.25 1.81 3.60

10 21 40 88 52 94 57 63 75 84

An accurately weighted quantity of the dye (0.1 mmol/L) was dissolved in deionized water to prepare the stock solution. Experimental solutions of the desired concentrations were obtained by successive dilutions.

where Ct (␮mol/L) is the dye concentration at time t (min), V is the volume of the solution (L), and m is the mass of adsorbent (g).

2.2. Adsorption experiments

3.1. Effect of initial solution concentration and pH on the dye removal

As the adsorption on activated carbon usually is performed in no flow systems, batch equilibrium experiments were carried out by shaking continuously the mixture of 0.5 g adsorbent AC or MN 200 with 25 mL of a given initial concentration of aqueous dye solution. Concentration of dye solution in the series ranged from 4 to 100 ␮mol/L. The pH values of initial solutions were measured and adjusted with 1 M HCl. After sorption they were rechecked and the change (decrease or increase) in solution pH was estimated. After attainment of adsorption equilibrium, the samples were centrifuged and the residual concentration of dye ascertained by an UV-Vis Spectrometer Cintra 101 (GBS Scientific Equipment (USA) LLS) at the respective max value, which is 616 nm for this dye. Dye concentration was calculated from the calibration curve. Residual color, Res (%), was calculated by comparing the absorption (A) of the treated sample with reference treated identically, but without adsorbent: Res (%) =

A (sample) × 100%, A (reference)

(1)

This was necessary because the molar extinction coefficient of the dyes changes with pH. Residual concentration of dye, C (␮mol/L), was calculated by multiplying the residual color by the original concentration: C = Res · C0 ,

(2)

where C0 (␮mol/L) is the initial concentration. The chemical oxygen demand (COD) values of the dye solutions were determined using a Spectroquant TR 320—Spectroquant Picco analyser (Merck KgaA, Germany). The concentration of chromium was determined using atomic absorption spectrometry (Perkin Elmer 603, USA) at the respective max = 358.2 nm. Kinetic values of batch adsorption were determined by analyzing the adsorptive uptake of the dye used from 100 ␮mol/L dye solution concentration at different time intervals at 20 and 40 ◦ C temperatures. This temperature interval was chosen considering a regulation for textile wastewater discharge in sewerage (<45 ◦ C) [9]. The amount of dye, qt (␮mol/g), adsorbed at time t was calculated: qt =

(C0 − Ct )V , m

(3)

3. Results and discussion

The effect of solution concentration and pH on dye removal from solution was studied under identical conditions for both activated carbon and Macronet MN 200. The values of the dye initial solution concentration ranged from 4 to 100 ␮mol/L at pH 2 and pH 7. The dye removal efficiency was characterized by the values of the residual color, Res (%), which depended on initial concentration of the dye (Table 1). The removal efficiency of the dye increased at lower concentrations, whereas it decreased at high concentrations. At lower initial dye concentration sufficient adsorption sites with the maximum adsorption potential are available for the sorption of dye molecules. However, at higher concentrations the ratio of number of dye molecules to the available adsorption sites is high and consequently the removal efficiency of dye decreases. The distribution of adsorption surface sites and their accessibility is determined by the surface chemistry and structural characteristics of the sorbents. With the view of the commercial dye used, the characteristics of treated dye solutions using activated carbon were compared with those of solutions treated using Macronet MN 200. The variations in removal of hazardous components such as chromium and organic substances, including azo compounds (chemical oxygen demand (COD)) at various pH and the initial dye solution concentration using activated carbon and Macronet MN 200 are shown in Table 1. It is evident that a higher removal of hazardous components was reached from acidic solutions. Activated carbon removed chromium below the residual concentration of 0.4 mg/L when the initial concentration of dye was lower than 30 ␮mol/L, while the removal of organics below values of chemical oxygen demand lower than 125 mgO2 /L was reached when the initial concentration of dye was below 50 ␮mol/L. The maximum removal of chromium ions using Macronet MN 200 was obtained when the initial concentration of chromium complex dye ranged from 4 to 50 ␮mol/L, while maximum removal of organics when the initial concentration was lower than 100 ␮mol/L. The removal of the chromium complex dye from an aqueous solution is dependent on pH of the solution, which affects the surface charge of the adsorbent. The removal of dye is more effective in acidic media (pH ≤ 2) as compared to that at pH ≥ 7 for both activated carbon and Macronet MN 200 (Table 1). Whereas under identical conditions dye removal using Macronet MN 200 is more effective than that using activated carbon (e.g., for Macronet MN 200 the residual color at pH ≤ 2 and initial concentration increasing from 4 to 100 ␮mol/L was below 10%, however for activated

936

D. Kauˇspedien e˙ et al. / Journal of Hazardous Materials 179 (2010) 933–939 ˙

carbon the residual color increased from 10% to 60% with increase in the initial concentration). In aqueous solutions, the dye molecule (the salt consisting from a medium strong acid and a strong base) (Fig. 1) was dissolved and the medium strong sulfonate groups of the chromium complex dye were dissociated and converted to anionic dye ions [28,32]: R  (SO3 )2 Na2 → R  (SO3 )2 2− + 2Na+

(4)

Depending on solution pH, protonation/deprotonation of surface functional groups create an electrical charge and hence a potential on the surfaces of adsorbents [33,34], which may further facilitate or complicate the adsorption of dye. The AC and Macronet MN 200 total surface charges measured as points of zero charge (pHpzc ) were determined comprehensively by all the functional groups, previously [35]. In reference to activated basic carbon with a pHpzc 9.95, neutral Macronet MN 200 showed a lower pHpzc by about 6.35 pH units (pHpzc 3.60). These results are in agreement with the data of Boehm titration. It was apparently due to a much higher phenolic hydroxyl group concentration of the Macronet MN 200 as compared to the AC: AC displayed a low acidity of 0.03 mmol/g but a high basicity of 0.5 mmol/g, while neutral Macronet MN 200 showed a total acidity above 6 times that of activated carbon, contributed from phenolic groups [35]. The pHpzc values of both adsorbents AC and MN 200 are higher than the equilibrium solution pH, indicating the occurrence of a positive charge in the whole net of both adsorbents in the acidic solution favorable for dye anion adsorption. Whereas, during the dye adsorption on activated carbon from the neutral solution, pH value increases from 7 to about 10 (Table 1) and the surface of activated carbon becomes increasingly negatively charged, consequently electrostatic repulsive interactions become more important. It could be the reason for lower dye adsorption by activated carbon from the neutral solution when compared to MN 200. At pH lower than pHpzc the presence of significant positive zeta potential on the MN 200 surface was attributed only to the presence of oxygen in the framework of this adsorbent [18,36]. Oxygencontaining groups (carbonyl, esters and alcohols) on the surface of polymer beads might originate from grafted or entangled chains of the surfactants employed in suspension polymerization. The anion adsorption properties (electrostatic interaction) were attributed to the following possibilities: +

+

C = OH ↔C–OH ↔ delocalized charge in the polymer framework. In addition, the presence of these groups results in a partially hydrophilic character of the polymer structure that could be also favoring the sorption of present in the solution anionic species. The basic character of AC arises primarily due to the delocalized ␲-electrons on the condensed polyaromatic sheets [37]. The FTIR spectrum of activated carbon (Fig. 2) shows a strong band at 1600 cm−1 due to C C skeletal stretching vibrations in aromatic rings. The presence of C O peak around 1650 cm−1 can be assigned to quinone, ketone and pyrone structures. The peak at 2300 cm−1 may be attributable to physisorbed carbon dioxide and ketone surface groups. The peak appeared at 1240 cm−1 may be assigned to ether, epi-oxide and phenolic structures in various chemical environments. In the recorded spectrum in the 3200–3600 cm−1 range a band of O–H stretching vibrations, due to the existence of surface hydroxylic groups and chemisorbed water was also observed [38]. The dye sorption on the activated basic carbons surface proceeds by two parallel mechanisms, one involving dispersive interactions and a second one involving electrostatic interactions [39]. The activated basic carbons are characterized by a high content of electron rich sites on the surface and a low concentration of electronwithdrawing groups. The interaction of the molecules of dyes and activated carbon surface is expected to occur between the delocal-

Fig. 2. FTIR spectrum of activated carbon.

ized ␲ electrons of the oxygen-free Lewis basic sites and the free electrons of the dye molecule present in the aromatic rings and multiple bonds. The oxygen-free carbon sites can adsorb protons from the solution, offering a positively charged surface to the carbon. Thus, it is possible that negatively charged ions of dye interact with these sites. 3.2. Kinetics of adsorption The time-dependent behavior of the dye adsorption was examined by varying the contact time between the adsorbent and the dye solution in the range of 5–60 min. The amount of dye qt (␮mol/g) plotted as a function of contact time t (Fig. 3(a) and (b)) showed that the dye adsorption approached equilibrium within shaking 10–15 min at the initial pH 2 and within 15–30 min at pH 7. In the first 30 min, 98% of the dye adsorption by MN 200 occurred at pH 2 and temperature of 20 ◦ C, whereas 88% of the adsorption did at pH 7 and the same temperature. When the temperature was 40 ◦ C and the solution pH ≤ 2, the dye adsorption of 95% by activated carbon was achieved in the first 30 min. However only 80% of dye adsorption occurred at pH values ≥7 and the same temperature of 40 ◦ C. In acidic solutions the electrostatic attractive interactions can increase the dye adsorption rate. A fast sorption process of Acid red 14 dye by MN 200 in acidic media was also reported [28]. A number of the sorption rate control mechanisms for dyeactivated carbon systems are suggested [40]. External or internal diffusion can be controlling depending on the way in which adsorbent is contacted with the dye solution. External diffusion is most effective within column adsorption processes, while intraparticle diffusion is dominant in batch (no flow) systems where a longer contact time is available. Uptake includes several ways of interaction such as chemisorption, physisorption, ion exchange, or complexation [41]. All the design tools developed have been based on simple models, using chemical interpretation of the adsorptive process; design equations are based on reaction rate constants [42]. Analyses of the respective batch rate with two theoretical models (pseudo-second-order and intraparticle diffusion) were used to describe the chromium complex dye sorption kinetics, and, simultaneously, to determine the sorption rate constants as well as

D. Kauˇspedien e˙ et al. / Journal of Hazardous Materials 179 (2010) 933–939 ˙

937

Fig. 3. Kinetic curves for the adsorption of chromium complex dye on activated carbon Norit RB 0.8 CC (AC) and Macronet MN 200 at different initial pH values and temperatures: experimental (a and b); tests of the pseudo-second-order-reaction model equation (c and d) and the intraparticle diffusion model equation (e and f). Conditions: mass of sorbent 0.5 g; initial chromium complex dye solution concentration 100 ␮mol/L.

elucidate the controlling step of dye diffusion by graphical analysis of the experimental data. The pseudo-second-order sorption model was selected because it is no need to know the equilibrium capacity from the experiments, as it can be calculated from the model [43,44]. In addition, the initial sorption rate can also be obtained from the model. The adsorption of chromium complex dye on activated carbon and MN 200 follows the pseudo-second-order kinetic model, which is expressed as [43,44]: dqt = k2 (qe − qt )2 dt

(5)

where k2 (g/(␮mol min)) is the pseudo-second-order rate constant; qt (␮mol/g) and qe (␮mol/g) the amount of dye adsorbed at time t and at equilibrium, respectively. Integration of Eq. (5) and application of the conditions qt = 0 at t = 0 and qt = qt at t = t, give 1 1 = + k2 t qe − qt qe

(6)

The following equation can be obtained on rearranging Eq. (6) into a linear form: 1 1 t = + t qt qe k2 q2e

(7)

k2 and qe can be obtained from the intercept and slope. The plot of t/qt vs. t shows a linear relationship for activated carbon and MN 200 (Fig. 3(c) and (d)). qe and k2 values were determined from the slope and intercept of plot, respectively and are given in Table 2. The correlation coefficients (R2 ) are high, in the range of 0.9730–0.9998, confirming a good agreement with the experimental data. The pseudo-second-order rate constant k2 for chromium complex dye sorption on AC with an increase in solution temperature from 20 to 40 ◦ C indicates an increase from 0.56 to 0.97 g/(␮mol min) at the pH ≤2 and decrease from 10.49 to 1.76 g/(␮mol min) at pH ≥7, whereas the equilibrium adsorption capacity qe increases with increase in temperature (Table 2). However, k2 values for dye adsorption onto Macronet MN 200 with an increase in temperature decrease from 1.64 to 1.37 g/(␮mol min) at pH ≤2 and from 1.11 to 0.79 g/(␮mol min) at pH 7 whereas the

938

D. Kauˇspedien e˙ et al. / Journal of Hazardous Materials 179 (2010) 933–939 ˙

Table 2 The parameters of pseudo-second-order kinetic, correlation coefficients obtained for the adsorption of chromium complex dye at different temperatures and pH. Conditions: adsorbent mass 0.5 g; volume of solution 25 mL; C0 = 100 ␮mol/L. T (◦ C)

20 40 20 40

pH

≤2 ≥7

AC Norit RB 08.CC

Macronet MN 200

k2 (g/␮mol min)

qe (␮mol/g)

R2

k2 (g/␮mol min)

qe (␮mol/g)

R2

0.56 0.97 10.49 1.76

0.73 0.99 0.06 0.10

0.9964 0.9730 0.9927 0.9757

1.64 1.37 1.11 0.79

1.16 1.20 0.32 0.34

0.9998 0.9996 0.9929 0.9914

Table 3 Intraparticle diffusion parameters, correlation coefficients obtained for the adsorption of dye at different temperatures and pH values. Conditions: adsorbent mass 0.5 g; volume of solution 25 mL; C0 = 100 ␮mol/L. T (◦ C)

pH

Activated carbon Norit RB 08.CC 0.5

ki (␮mol/g min 20 40

≤2 ≥7 ≤2 ≥7

0.049 0.007 0.031 0.009

)

Macronet MN 200 2

A (␮mol/g)

R

ki (␮mol/g min0.5 )

A (␮mol/g)

R2

0.363 0.014 0.756 0.031

0.8014 0.9219 0.9889 0.7514

0.025 0.022 0.023 0.026

0.983 0.156 1.025 0.141

0.7910 0.8888 0.8548 0.9692

equilibrium adsorption capacity increases. Consequently it may be concluded that the chromium complex dye adsorption mechanism onto both adsorbents does not follow exclusively a physisorption mechanism, when generally increase in temperature increases the rate of attainment of equilibrium, and decreases the equilibrium adsorption, but other processes also occur [45]. Endothermic nature of the adsorption process might be due to the chemical interaction between the dye molecules and the chemical functional groups on the surface of adsorbents. The adsorption of metal complex dye by activated carbon was favored at higher temperature and lower solution pH. This is partly due to the strong forces of attractions at higher temperature. The mechanism of the metal complex dye–adsorbent interaction is likely to be complicated involving physisorption and chemisorption. Additionally, the influence of the diffusion process on dye removal was also considered. The pseudo-second-order kinetic model cannot identify the diffusion mechanism and the kinetic results were then analyzed by using the intraparticle diffusion model. According to this model, the initial rate of intraparticle diffusion is given by the equation [46]: qt = ki t 0.5 + A

(8)

where qt (␮mol/g) is the amount of dye on the surface of the adsorbent at time t, ki (␮mol/g min0.5 ) is the intraparticle diffusion rate constant, t (min) is the time and A (␮mol/g) is the intercept. According to this model, the plot of qt vs. the square root of time (t0.5 ) for dye sorption on activated carbon and on Macronet MN 200 (Fig. 3(e) and (f)) would be linear if intraparticle diffusion were involved in the adsorption process and if these lines passed through the origin, intraparticle diffusion would be the rate determining step [47]. When the plots obtained for the dye sorption on activated carbon and MN 200 do not pass through the origin, this is indicative of some degree of boundary layer control and this further shows that the intraparticle diffusion is not the only ratelimiting step, but also other kinetic models may also control the rate of adsorption with all of them operating simultaneously. The slope of intraparticle diffusion plots can be used to derive values for the rate parameter ki , for the intraparticle diffusion, given in Table 3. The correlation coefficients (R2 ) for the intraparticle diffusion model are between 0.7514–0.9889 for activated carbon and 0.7910–0.9692 for Macronet MN 200. This indicates that chromium complex dye adsorption on AC, as well as on Macronet MN 200 may be followed by the intraparticle diffusion model up to 60 min. The values of intercept A may be used for indirect characterization of the boundary layer thickness that means that the larger the intercept

the greater the boundary layer effect is [48]. The boundary layer effect on chromium complex sorption is more pronounced in acidic solutions (Table 3) and it increases with increase in temperature, especially in the case of AC at pH ≤2. 4. Conclusions The neutral hyper-cross-linked polymeric adsorbent Macronet MN 200 was shown to be more effective in removing anionic dye Lanasyn Navy M-DNL (chromium complex dye) than activated carbon Norit RB 08.CC. The extent of removal depends on the chromium complex dye concentration, solution pH and temperature. The removal efficiency of color as well as hazardous components such as chromium and organic substances, including azo compounds, increases at low concentrations, whereas it decreases at high concentrations. The pH of the solution affects the surface charge of the adsorbent: in acidic media the surface of both MN 200 and AC develops a positive net charge (pHpzc > pH 2;) favorable for dye anion adsorption. The kinetic data obtained showed faster dye removal for both adsorbents in acidic media. The correlation coefficients (R2 ) in the range of 0.9730–0.9998 confirmed that the secondorder kinetic model described properly the experimental sorption data. The rate of dye adsorption on both adsorbents depends on diffusion, with a higher boundary layer effect on diffusion at the initial solution pH ≤2 especially on MN 200. Acknowledgements The authors wish to thank the Clariant (Schweiz) for the dye. Thanks belong to Purolite International Ltd. (UK) for providing the polymeric adsorbent and to Norit Company (Netherlands) for activated carbon. References [1] W. Delee, C. O’Neil, F.R. Hawkes, H.M. Pinheiro, Anaerobic treatment of textile effluents: a review, J. Chem. Technol. Biotechnol. 73 (1998) 323–335. [2] I.G. Laing, The impact of effluent regulation on the dye industry, Rev. Prog. Color 21 (1996) 56–71. [3] V.M. Correia, T. Stephenson, S.J. Judd, Characterisation of textile wastewaters—a review, Environ. Technol. 15 (1994) 917–926. [4] J.M. Chern, S.N. Huang, Study of non-linear wave propagation theory. 1. Dye adsorption by activated carbon, Ind. Eng. Chem. Res. 37 (1) (1998) 253–257.

D. Kauˇspedien e˙ et al. / Journal of Hazardous Materials 179 (2010) 933–939 ˙ [5] Y. Al-Degs, M.A.M. Khraisheh, S.G. Allen, M.N. Ahmad, Effect of carbon surface chemistry on the removal of reactive dyes from textile effluent, Water Res. 34 (3) (2000) 927–935. [6] K. Hunger (Ed.), Industrial Dyes. Chemistry, Properties, Application, Wiley-VCH, Weinheim, 2003. [7] T. Poiger, S.D. Richardson, G.L. Baughman, Analysis of anionic metallized azo and formazan dyes by capillary electrophoresis–mass spectrometry, J. Chromatogr. A 886 (2000) 259–270. [8] C.Y. Kim, H.M. Choi, H.T. Cho, Effect of deacetylation on sorption of dyes and chromium on chitin, J. Appl. Polym. Sci. 63 (6) (1998) 725–736. [9] Environmental Agency, Guidance for Textile sector, Integrated Pollution Prevention and Control (IPPC), IPPC S6.05, 2002. [10] Ministry of Environment of the Republic of Lithuania, Regulations of Waste Water Effluents, October 2007. [11] S. Mondal, Methods of dye removal from dye house effluent—an overview, Environ. Eng. Sci. 25 (3) (2008) 383–396. [12] Ch.Y. Yin, M.K. Aroua, W.M.A.W. Daud, Review of modifications of activated carbon for enhancing contaminant uptakes from aqueous solutions, Sep. Purif. Technol. 52 (2007) 403–415. [13] P. Faria, J. Orfao, M. Pereira, Adsorption of anionic and cationic dyes on activated carbons with different surface chemistries, Water Res. 38 (2004) 2043–2052. [14] V. Gomez, M.S. Larrechi, M.P. Calao, Kinetics and adsorption study of acid dye removal using activated carbon, Chemosphere 69 (2007) 1151–1158. [15] Y.S. Al-Degs, M.I. El-Barghouthi, A.H. El-Sheikh, G.M. Walker, Effect of solution pH, ionic strength, and temperature on adsorption behavior of reactive dyes on activated carbon, Dyes Pigments 77 (2008) 16–23. [16] X Yang, B. Al-Duri, Kinetic modeling of reactive dyes on activated carbon, J. Colloid Interface Sci. 287 (2005) 25–34. [17] C.A. Leon y Leon, J.M. Solar, V. Calemma, L.R. Radovic, Evidence for the protonation of basal plane sites on carbon, Carbon 30 (1992) 797–811. [18] M. Streat, L.A. Sweetland, Physical and adsorptive properties of HypersolMacronetTM polymers, React. Func. Polym. 35 (1997) 99–109. [19] A. Özcan, E.M. Öncü, A.S. Özcan, Kinetics, isotherm and thermodynamic studies of adsorption of Acid Blue 193 from aqueous solutions onto natural sepiolite, Colloids Surf. A: Physicochem. Eng. Aspect 277 (2006) 90–97. [20] S. Kärcher, A. Kornmüller, M. Jekel, Screening of commercial sorbents for the removal of reactive dyes, Dyes Pigments 51 (2001) 111–125. [21] M. Leszczynska, Z. Hubicki, Application of weakly and strongly basic anion exchangers for the removal of Brilliant Yellow from aqueous solutions, Desalination Water Treat. 2 (2009) 156–161. [22] M. Wawrzkiewicz, Z. Hubicki, Equilibrium and kinetic studies on the adsorption of acidic dye by the gel anion exchanger, J. Hazard. Mater. 172 (2009) 868–874. [23] M. Wawrzkiewicz, Z. Hubicki, Kinetic studies of dyes sorption from aqueous solutions onto the strongly basic anion-exchanger Lewatit MonoPlus M-600, Chem. Eng. J. 150 (2009) 509–515. [24] M. Wawrzkiewicz, Z. Hubicki, Removal or tartrazine from aqueous solutions by strongly basic polystyrene anion exchange resins, J. Hazard. Mater. 164 (2009) 502–509. [25] M. Greluk, Z. Hubicki, Sorption of SPADNS azo dye on polystyrene anion exchangers: equilibrium and kinetic studies, J. Hazard. Mater. 172 (2009) 280–297. [26] Z.Y. Hu, Q.X. Zhang, H.P. Fang, Applications of porous resin sorbents in industrial wastewater treatment and resource recovery, Crit. Rev. Environ. Sci. Technol. 33 (2003) 363–389. [27] Y. Yu, Y.Y. Zhang, Z.H. Wang, M.Q. Qui, Adsorption of water-soluble dyes onto modified resin, Chemosphere 54 (2004) 425–430.

939

[28] C. Valderrama, J.L. Cortina, A. Farran, F. Gamisans, F.X. de las Heras, Evaluation of hyper-cross-linked polymeric sorbents (Macronet MN200 and MN300) on dye (Acid red 14) removal process, React. Funct. Polym. 68 (2008) 679–691. [29] C. Valderrama, J.L. Cortina, A. Farran, X. Gamisans, F.X. de las Heras, Kinetic study of acid red “dye” removal by activated carbon and hyper-cross-linked polymeric sorbents Macronet Hypersol MN200 and MN300, React. Funct. Polym. 68 (2008) 718–731. [30] E. Belston, D. Naden, The Technocom process, in: Proceedings of the International Conference on Water and Textiles, University of Huddersfield, 1999. [31] S. Dragan, M. Cristea, A. Airinei, I. Poinescu, C. Luca, Sorption of aromatic compounds on macroporous anion exchangers based on polyacryloamide: relation between structure and sorption behavior, J. Appl. Polym. Sci. 55 (1995) 421–430. [32] N. Sakkayawong, P. Thiravetyan, W. Nakbanpote, Adsorption mechanism of synthetic reactive dye wastewater by chitosan, J. Colloid Interface Sci. 286 (2005) 36–42. [33] J.S. Mattson Jr., H.B. Mark, Activated Carbon: Surface Chemistry and Adsorption from Solution, Marcel Dekker, New York, 1971. [34] Y. Qui, F. Ling, Role of surface functionality in the adsorption of anionic dyes on modified polymeric sorbents, Chemosphere 64 (2006) 963–971. ˙ D. Kauˇspedien ˙ ˙ A. Gefeniene, ˙ A. Selskiene, ˙ R. Binkiene, ˙ Sorp[35] E. Kazlauskiene, e, tion of chromium complex dye on activated carbon and neutral polymeric adsorbent, Chemija 20 (2) (2009) 69–77. [36] N.A. Penner, P.N. Nesterenko, Anion-exchange ability of neutral hydrophobic hypercrosslinked polystyrene, Anal. Commun. 36 (1999) 199–201. [37] R.U. Detlef, Knappe, Effects of Activated Carbon Characteristics on Organic Contaminant Removal, Awwa Research Foundation, Denver, CO, 2003. ´ atkowski, ˛ [38] M. Pakuła, M. Walczyk, A. Biniak, A. Swi Electrochemical and FTIR studies of the mutual influence of lead(II) or iron(III) and phenol on their adsorption from aqueous acid solution by modified activated carbons, Chemosphere 69 (2007) 209–219. [39] I.I. Salame, T.J. Bandosz, Experimental study of water adsorption on activated carbons, Langmuir 15 (1999) 587–593. [40] M.A.M. Kharaisheh, Y.S. Al-Degs, S.J. Allen, M.N. Ahmad, Elucidation on controlling steps of reactive dye adsorption on activated carbon, Ind. Eng. Chem. Res. 41 (2002) 1651–1657. [41] W.J. Weber, F.A. DiGiano, Process Dynamics in Environmental Systems, Wiley & Sons, New York, 1996. [42] A.R. Gavaskar, Design and construction techniques for permeable reactive barriers, J. Hazard. Mater. 68 (1999) 41–71. [43] Y.S. Ho, Review of second-order models for adsorption systems, J. Hazard. Mater. B136 (2006) 681–689. [44] Y.S. Ho, G. McKay, Pseudo-second order model for sorption processes, Process. Biochem. 34 (1999) 451–465. [45] F. Güzel, H. Yakut, G. Topal, Determination of kinetic and equilibrium parameters of the batch adsorption of Mn(II), Co(II), Ni(II) and Cu(II) from aqueous solution by black carrot (Daucus carota L.) residues, J. Hazard. Mater. 153 (2008) 1275–1287. [46] W.J. Weber, J.C. Morris, Kinetics of adsorption on carbon materials, J. Sanitary Eng. Div. Am. Soc. Civ. Eng. 89 (1963) 31–56. [47] N. Kannan, M.M. Sundaram, Kinetics and mechanism of removal of methylene blue by adsorption on various carbons—a comparative study, Dyes Pigments 51 (1) (2001) 25–40. [48] A. Özcan, M. Öncü, A.S. Özcan, Adsorption of Acid Blue 193 from aqueous solutions onto DEDMA-sepiolite, J. Hazard. Mater. B129 (2006) 244–252.