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Synthesis of zeolite from sugarcane bagasse fly ash and its application as a low-cost adsorbent to remove heavy metals
Journal of Cleaner Production 229 (2019) 956e963
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Synthesis of zeolite from sugarcane bagasse fly ash and its application as a low-cost adsorbent to remove heavy metals ssica A. Oliveira, Felipe A. Cunha, Luís A.M. Ruotolo* Je ~o Carlos, Rod. Washington Luiz km 235, 13565-905, Sa ~o Carlos, SP, Brazil Department of Chemical Engineering, Federal University of Sa
a r t i c l e i n f o
a b s t r a c t
Article history: Received 8 January 2019 Received in revised form 17 April 2019 Accepted 7 May 2019 Available online 7 May 2019
A new clean and sustainable procedure to synthesize low-cost zeolites from sugarcane bagasse fly ash (BFA), an industrial waste, is presented. BFA is used as source of Al and Si to obtain aluminosilicates with distinguished ion exchange capacity, confirmed by copper uptake. After the fly ash has been calcined and submitted to hydrothermal treatment employing NaOH as mineralizing agent, the XRD patterns of the as-synthesized samples revealed the formation of zeolite Na-A. Temperature and calcination time are key parameters affecting the ion-exchange capacity (q) of the zeolitic materials. Calcination at 600 C for 8 h, under oxygen atmosphere, ensures that all carbon from fly ash has been removed and optimizes the ionexchange properties. As a strategy to further improve q, Al isopropoxide was added to the synthesis medium, reducing the Si/Al ratio in the zeolite and generating more ion exchange sites. The hydrothermal treatment and addition of Al modify the structure and morphology of the zeolitic material, leading to a maximized adsorption capacity (142 mg Cu2þ g-1) at 1.71 Si/Al, which is much higher than the observed for a commercial polymeric resin (46.6 mg g-1). © 2019 Elsevier Ltd. All rights reserved.
Keywords: Na-A Sugarcane bagasse fly ash Adsorbent Ion-exchange Heavy metal
1. Introduction The synthesis of zeolites using biowaste as source of Al and Si has been investigated by many authors in the last few years (Belviso, 2018; Ma et al., 2015). Among the numerous applications of zeolites, their use as cation exchangers for effluent treatment or metal removal is well known. Zeolites are crystalline aluminosilicates with three-dimensional structures formed by tetrahedrons composed by Si and Al bounded by oxygen atoms. The presence of Al3þ in the zeolite framework results in a negative net charge neutralized by compensation cations, which are responsible by the ion exchange property of these materials. Additionally, the microporous structure with well-defined size cavities, besides the high surface area, also provides selectivity, adsorption, and catalytic properties (Nibou et al., 2010). In the last few decades, the use of inorganic (Asl et al., 2019; Rashidi and Yusup, 2016) and biomass wastes (Kim et al., 2018) have been reported as precursors for the synthesis of zeolitic materials (Belviso, 2018). A typical example is the use of coal fly ash from coal-fired thermal power plants to synthesize zeolite A
* Corresponding author. E-mail address: [email protected] (L.A.M. Ruotolo). https://doi.org/10.1016/j.jclepro.2019.05.069 0959-6526/© 2019 Elsevier Ltd. All rights reserved.
(Goscianska et al., 2018), X, faujasite-type (Chang and Shih, 2000; Volli and Purkait, 2015), beta (Assawasangrat et al., 2016), Y (Rayalu et al., 2000), erionite ZSM-18, linde (Koukouzas et al., 2009), F linde, kalsilite, philipsite-KM (Querol et al., 1997), analcite, hydroxy sodalite (Lin and Hsi, 1995), and P (Fungaro and Bruno, 2009; Murayama et al., 2002). Among the biomass precursors, fast kinetics and high removal capacity have been reported for zeolites synthesized using rice husk as source of Al and Si (Dalai et al., 1985; Saceda et al., 2011). Despite this plethora, reports on zeolites synthesis from bagasse fly ash are still scarce in literature. The sugarcane bagasse fly ash (BFA) is produced in large amounts in sugar and ethanol plants after burning biomass to generate power and steam and results from the incomplete burn of the bagasse. Hence, finding a cleaner process to add value and give a final destination to this solid waste is of great interest from the environmental and economic point of view. Since BFA is mainly composed by unburned carbon, SiO2 and Al2O3 (Gupta and Sharma, 2003), here we studied the conversion of this waste into aluminosilicates to obtain a low-cost ion exchange materials. According to Shah et al., zeolite P and analcime are the main zeolitic material obtained after the hydrothermal treatment of the as-received BFA; their uptake capacity was confirmed towards 2chlorophenol (Shah et al., 2011a), phenol (Shah et al., 2011b, 2012a), dye (Shah et al., 2011c, 2011d), and p-nitrophenol (Shah
J.A. Oliveira et al. / Journal of Cleaner Production 229 (2019) 956e963
et al., 2012b) adsorption in batch and column. Purnomo (2013) extracted the silicon and aluminum from bagasse fly ash to synthetize Na-X and Na-A zeolites. In this process, Si and Al were separated from carbon by mixing the fly ash with NaOH, followed by heating at 500 C and then washing the resulting fused material with deionized water to obtain Si and Al ions. Na-A zeolite was also obtained by Moises et al., 2013, 2014, but instead of BFA, the bagasse bottom ash was used as primary source of Al and Si. Recently, Shah et al., 2017a, 2017b reported the preparation of zeolitic materials employing microwave hydrothermal treatment and their application to o-chlorophenol and aniline adsorption. In these works, BFA is used directly to obtain the zeolites or complicated procedures are utilized to extract the Si and Al. Differently, to the best of our knowledge, here we report for the first time the synthesis of zeolites using the BFA ash obtained after thermal treatment to remove the unburned carbon. Furthermore, only few authors explored the ion exchange properties of the zeolites prepared from low-cost sources to remove heavy metals. In this work we investigated the use of BFA as source of Si and Al to obtain low-cost zeolitic materials with distinguished cation exchange properties. The new procedure employed to obtain zeolites is clean and sustainable since it replaces, totally or partially, the usual Si and Al precursors (tetraethyl orthosilicate and aluminum isopropoxide, respectively) by an abundant source of these elements present in BFA. Different temperature and calcination time are investigated to remove the remaining carbon in BFA and increase the Si and Al content. To further improve the ion exchange capacity, we also investigate the effect of reducing the Si/Al ratio by adding Al isopropoxide in the gel synthesis. As far as we know, this procedure has not been reported before for synthesis of zeolitic materials using BFA. The ion exchange capacity of the assynthetized materials is investigated towards Cu2þ uptake. Copper was chosen because of the large volume of effluents generated in many industrial processes, which is commonly removed by ion exchange using expensive polymeric resins.
957
2. Experimental 2.1. Materials BFA was collected at the exit of a gas washing tower from a sugar mill and ethanol plant. After washing, the fly ash was calcined at different temperatures under O2 atmosphere in order to obtain the ash, mostly composed by Si and Al (Gupta and Sharma, 2003). The ash was submitted to hydrothermal treatment in the presence of 3.5 mol L-1 NaOH (Sigma-Aldrich) to obtain the zeolitic material. In some experiments, aluminum isopropoxide, C9H21O3Al (SigmaAldrich), was added to the synthesis medium. CuSO4.5H2O (Synth) was used as source of Cu2þ in the ion exchange experiments. All solutions were prepared using deionized water. 2.2. Zeolite synthesis The BFA was previously separated from sand and other contaminants by flotation, dried in an oven at 100 C, grinded and sieved. The particles with diameters lower than 38 mm were calcined in a furnace (EDG 7000), under O2 atmosphere, at different temperature and calcination time. The as-obtained ash was submitted to hydrothermal synthesis applying the conditions described in Table 1 and illustrated in Fig. 1. The reaction vessel is a PTFE lined autoclave. After 24 h, the material was washed with deionized water until constant pH, filtered, and dried at 60 C for 24 h. The samples were coded according to the treatment procedure, temperature, and calcination time, respectively; e.g. H-600-8 indicates that the material was synthesized according to procedure H using the ash obtained after fly ash calcination at 600 C for 8 h. In the case in which Al isopropoxide was added to synthesis gel, the ash C-600-8 was used in all experiments and the samples were labeled according to the Si/Al ratio in the solid phase, e.g. HIeSi/Al1.71.
Table 1 Procedures employed for the treatment of BFA. Procedure
Description
C H HI
BFA was only calcined employing different temperatures and times Calcination followed by hydrothermal reaction in autoclave containing 3.5 mol L-1 NaOH and maintained in an oven at 100 C, for 24 h Similar to procedure H, but adding Al isopropoxide
Fig. 1. Schematic representation of the zeolite synthesis.
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2.3. Characterization Thermogravimetric analysis (Mettler Toledo TGA/SDTA851e) was performed at room temperature, using a heating rate of 15 C min1 in nitrogen and oxygen (60 mL min1). The phase composition was determined from X-ray diffraction (XRD) recorded on a Siemens D5005 diffractometer using a Ni-filtered Cu Ka radiation (l ¼ 1.5418 Å) in a 2q range between 5 and 65 at 2 min-1. Search Match software was used to index the crystallographic phase. SEM images were obtained in a Philips XL30 FEG microscope. The X-ray fluorescence (XRF) analysis was performed in an EDX 720 Shimadzu in dispersive energy mode. The zeta potential was measured for different values of pH using a Zetasizer Nano ZS system (Malvern Instruments). The Si and Al content in C-600-8 was determined by inductively coupled plasma optical emission spectrometry (ICP-OES) using a Thermo Scientific iCAP6000.
Residual mass / W W0-1
1.0 0.8 0.6
BFA - N2 BFA - O2
0.4 0.2 0.0
200
400
(a)
q¼
V ðC0 CÞ ms
(1)
The influence of pH on the ion-exchange was studied employing the same procedure, but contacting 50 mg of adsorbent with 40 mL of 93.0 mg L-1 Cu2þ solution with values of pH varying from 1.0 to 4.5 (adjusted using sulfuric acid). The concentrations of Cu2þ were established considering the values commonly found in industrial effluents treated by adsorption. The isotherms were obtained following the same procedure described before, but contacting 50 mg of adsorbent with different concentrations of Cu2þ (50 mL). A Dubnoff shaking water bath was used to control the temperature in these experiments. 3. Results and discussion 3.1. Effect of calcination Fig. 2a shows the thermogravimetric curves for BFA recorded in N2 and O2 atmospheres. Under oxygen, the weight loss observed until 200 C is ascribed to water removal, while the weight loss in the range between 350 and 580 C regards to the burn of carbon and organic residues, which are completely eliminated at ~900 C (87% weight loss), remaining only the inorganic compounds. On the other hand, under N2, the remaining mass is composed by carbon and inorganics. Hence, according to the mass balance, the BFA composition is estimated as 7.1% water, 17.5% volatiles, 62.4% fixed carbon, and 13.0% ash. Taking into account the results from Fig. 2a, different calcination temperatures were applied to determine the desired operational time to eliminate the remaining carbon from the fly ash (Fig. 2b). The normalized weight loss was defined as the ratio between the weight loss after calcination and the ash content determined in the
1000
1200
1400
100
Normalized weight loss / %
800
Temperature / °C
2.4. Ion exchange Ion exchange experiments were carried out to determine the ion-exchange capacity (q) as a function of the calcination and synthesis conditions. Erlenmeyers (125 mL), containing 50 mg of zeolite and 50 mL of Cu2þ solution, were submitted to orbital shaking at 150 rpm for 24 h in order to achieve the equilibrium. The solid phase was separated by centrifugation and the copper remained in the liquid phase was measured by atomic absorption spectrophotometry (Varian, model SpectrAA200). The copper concentration in the solid phase (q) was determined using Equation (1), in which V is the volume (L), ms mass of the adsorbent (g), Co the initial copper concentration (mg L-1), and C the copper concentration at equilibrium (mg L-1).
600
o
600 C o 800 C
80
60
40
20
0
0 10 min
(b)
1 h1
2 h2
3 h3
4 h4
5 h5
Calcination time
Fig. 2. (a) Thermogravimetric (TG) analyses of BFA in N2 and O2 atmospheres and (b) normalized weight loss as a function of time and calcination temperature (under oxygen atmosphere).
TG analysis, i.e., 13% w/w of the BFA mass. According to Fig. 2b, after applying 800 C (5 h), all carbon and volatiles are eliminated, resulting in a white ash containing Si and Al, among small fractions of other elements. Fig. 2b reveals that 4 h calcination at 600 C practically remove water and organic volatiles (~98%), while applying 800 C the maximum weight loss is achieved after 3 h. Although the faster kinetics, calcination at 800 C modifies the morphology and has deleterious effects on the ion exchange capacity of the synthesized zeolites. 3.2. Characterizations 3.2.1. Morphological and structural analysis Fig. 3 shows the SEM images of the samples submitted to calcination and hydrothermal treatment. After the bagasse burning, the BFA retains the morphological aspect of the precursor (Fig. 3a), which is not preserved after calcination. Although the ash does not exhibit a specific morphology (Fig. 3b), after the hydrothermal treatment it is converted to spherical particles, with diameters varying from 2 to 5 mm (Fig. 3c), containing the zeolitic material
J.A. Oliveira et al. / Journal of Cleaner Production 229 (2019) 956e963
959
Fig. 3. SEM images: (a) fly-ash, (b) C-600-4, (c)e(d) H-600-4, (e) H-600-8, and (f) H-800-4.
(Fig. 3d) similar to the obtained by authors using coal fly ash (Koukouzas et al., 2009; Singer and Berkgaut, 1995). The cenosphere morphology has been attributed to the presence of residual carbon, as in the case of C600-4. This is corroborated by the fact that after the hydrothermal treatment of C-600-8 (in which there is no residual carbon), cenospheres are not formed (Fig. 3e) and the resulting material has a distinct morphology (Fig. 3f). The XRD pattern of the fly ash shown in Fig. 4a confirms the
-SiO2 Zeolite Na-A H-800-4
Intensity / a.u.
H-800-4
H-600-4
Intensity / a.u.
H-600-4
C-600-4
C-600-4
fly ash
fly ash 0
(a)
10
20
30
40
2 / degree
50
60
70
22 23 24 25 26
(b)
28 30 32 34 36
2 / degree
Fig. 4. XRD patterns: (a) 5 2q 65 and (b) 22 2q 36 .
presence of Si as a-SiO2 (quartz low) (JCPDS 86e1628). The broad peak regards to the existence of disordered microcrystalline carbonized material with small amounts of amorphous phase of silica and/or alumina. After calcination and hydrothermal treatment, this broad peak disappears since most of the carbon has been removed. For samples C-600-4 and H-600-4, the a-SiO2 peaks persist and are even more intense, indicating that the resulting material presents more crystalline silica. On the other hand, the relative intensity of the secondary peaks for H-800-4 decreases, revealing that higher calcination temperatures affect not only the morphology (Fig. 3), but the crystallinity as well. Furthermore, after the hydrothermal treatment, new XRD peaks (Fig. 4b) reveals the synthesis of the Na-A zeolite (JCPDS 73e2340). Al isopropoxide was added to the synthesis medium as an attempt to decrease the Si/Al ratio and further improve the ion exchange properties. Prior these syntheses, the amount of Si and Al in C-600-8 was determined by ICP-OES, revealing the presence of 49 mg Al and 335 mg Si per gram of ash (Si/Al ¼ 6.8). The BFA composition was determined by mass balance using the percentages determined from the TG analysis (Fig. 2), giving 50 mg water, 124 mg volatiles, 442 mg fixed carbon and 384 mg ash per gram of BFA. Table 2 shows the Si/Al ratios in the synthesis medium and in the zeolitic material, determined by XRF. The samples were labeled as HIeSi/Al- followed by the Si/Al ratio in the solid. XRD patterns shown in Fig. 5a for the materials containing different Si/Al ratios follow the same trend observed in Fig. 4 and are mainly composed by a-SiO2 and Na-A zeolite. The HI-samples have similar structures with two weak peaks at 52 and 62
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60
Table 2 Si/Al ratio in the synthesis medium and in the zeolitic material. Si/Al (synthesis medium)
Si/Al (zeolitic material)x
HIeSi/Al-1.61 HIeSi/Al-1.71 HIeSi/Al-1.82 HIeSi/Al-2.04 HIeSi/Al-2.64 HIeSi/Al-3.83 H-600-8
1.3 2.0 2.3 3.0 3.8 5.1 6.8±
1.61 1.71 1.82 2.04 2.64 3.83 5.90
50
q / mg g
-1
Sample
The Si source is the C-600-8 and the Al sources are C-600-8 (49 mg Al g-1) and Al isopropoxide (27 mg Al g-1). ±Determined by ICP. xDetermined by XRF.
40
Zeta potential / mV
960
30 20 10 0 -10 -20
30
3
4
5
6
7
pH
20 10
attributed to Al2O3 (JCPDS 88e0107), revealing that part of the Al precipitates as oxide. Interestingly, H-600-8 presents more intense zeolite peaks than H-600-4, suggesting that longer calcination improves the zeolite crystallinity. The SEM images for HIeSi/Al-1.71 (Fig. 5bec) reveal a remarkable morphology change when the hydrothermal treatment is carried out in the presence of Al-isopropoxide. The rod-type shape of the particles is ~400 nm long (Fig. 5c), whose agglomerates form large sponge-like clusters (Fig. 5b). This same morphology is observed for HIeSi/Al-1.61, but disappear for Si/Al ratios higher than 1.82.
0 1
3
Fig. 6. Copper uptake and zeta potential (inset) as a function of pH. C0 ¼ 93 mg Cu2þ L, m ¼ 50 mg H-600-4, T ¼ 30 C.
precipitates after the addition of the aluminosilicate. Considering that the natural pH of the copper solutions is close to 4.5, this pH was employed in the next experiments. Fig. 7a shows the values of q for copper removal using the asreceived fly ash, the calcined fly ash, and the ash submitted to hydrothermal treatments. The low copper uptake for fly ash (Gupta and Sharma, 2003) and the calcined samples was already expected, but it is interesting to note how calcination at 800 C decreases q, even after the hydrothermal treatment, suggesting that the crystallinity loss observed in the XRD pattern (Fig. 4a) and the morphology change (Fig. 3a) have a deleterious effect on the ionexchange properties of these materials. The superior ion exchange performance of the materials
HI-Si/Al-3.83
Intensity / a.u.
HI-Si/Al-2.64 HI-Si/Al-2.04
HI-Si/Al-1.82 HI-Si/Al-1.71 HI-Si/Al-1.61 H-600-8 (Si/Al = 5.90)
(a)
10
20
30
40
50
60
5
1
As the pH affects the properties of the exchangeable ions and the surface charge of the solid phase, its influence on the ion exchange capacity was prior investigated. According to Fig. 6, the absence of adsorption at pH lower than 2.5 is attributed to the excess of protons that hinders the copper uptake due to the strong competition between Hþ and Cu2þ. As the pH approaches the isoelectric point at pH ~6.0 (inset Fig. 6), the copper uptake grows up to its maximum at 4.5. For pH higher than 4.5, copper immediately
0
4
pH
3.3. Cu2þ sorption
-SiO2 Zeolite Na-A Al2O3
2
70
2 / degree
Fig. 5. (a) XRD patterns for the samples with different Si/Al ratios; (bec) SEM images of HIeSi/Al-1.71: (b) 7500X and (c) 100000X.
00-3
H-800-4
C-80 0-4 C-800-5
00-3
sh
10
961
known (Chang and Shih, 2000; Purnomo et al., 2012). It is interesting to note the ion exchange capacity of HIeSi/Al-1.61 decreases, indicating that, despite the higher content of Al in the sample, likely it is not associated to the Na-A. Comparing the maximum ion exchange capacity obtained using HIeSi/Al-1.71 (142 mg g-1) with the obtained by Hirano and Gubulin (2000) using commercial polymeric resins (46.6 mg g-1) at the same temperature, material dosage, and copper concentration, it is evident the superior performance of the zeolitic material.
C-6 C-8
20
C-6
30
00-4
40
00-5 C-6 00-8
50
Fly a
qe / mg g
-1
60
H-8
H-6
00 - 4
70
H-6
80
00-5 H- 6 00 -8
J.A. Oliveira et al. / Journal of Cleaner Production 229 (2019) 956e963
3.4. Thermodynamics
0
Samples Fig. 7. Ion-exchange capacity of the different materials. C0 ¼ 82.7 mg Cu2þ L-1, m ¼ 50 mg, T ¼ 30 C.
obtained after hydrothermal treatment using the ash calcined at 600 C is ascribed to the formation of the Na-A zeolite. The lower values of q observed for the samples calcined for 4 and 5 h indicate that the presence of residual carbon, besides promoting the cenosphere morphology (Fig. 2b), also affects the ion exchange. Once removed the carbon, the ion exchange capacity reaches its maximum for HI-600-8. Therefore, the ash C-600-8 was chosen as precursor to investigate the hydrothermal synthesis varying the Si/ Al ratio. It is well known that the ion exchange property of aluminosilicates depends on the number of Al atoms in their structure, responsible for the negative charge in the zeolite framework, which is compensated by a cation, as schematized in the inset of Fig. 8. Therefore, the addition of Al in the synthesis medium was tested as a strategy to further improve the values of q. According to Fig. 8, the trend of Si/Al on the values of ion exchange capacity is more intensely manifested for values lower than 2.04, when large amounts of Al-isopropoxide is employed and alumina has been formed (Fig. 5a). The improved ion exchange capacity of these samples indicates that more Al atoms have been incorporated into the zeolitic material, providing negative charges which are compensated by Naþ from the synthesis medium. Moreover, the high cation exchange capacity of zeolite Na-A is well
According to the IUPAC classification, the type I isotherms shown in Fig. 9 for the copper uptake using HIeSi/Al-1.71 indicates that the sorbent has strong affinity for cations. The sorption data are best fitted to the Freundlich isotherm (Eq. (2)), suggesting that adsorption occurs in multilayers on a heterogeneous surface. In Eq. (2), Ce is the solute concentration in the liquid phase at equilibrium (mg L-1), 1/n is a dimensionless constant related to the surface heterogeneity, and KF is the Freundlich constant, related to the adsorption capacity (mg1(1/n) g-1 L1/n). The Freundlich constants and thermodynamic parameters are shown in Table 3 for three different temperatures. It is evident the detrimental effect of temperature on the adsorption process since KF decreases and 1/n increases, indicating less favorable isotherms. Considering that the higher 1/n the lowest the adsorbent/adsorbate affinity, lower values of 1/n are desirable in order to obtain better adsorption performances. 1=n
qe ¼ KF C e
(2)
The changes in free energy (DGo), enthalpy (DHo), and entropy (DSo) were calculated according to Eqs. (4)and (5), proposed by Milonji c (2007). The equilibrium constants (Ke), in L g-1, were calculated by Eq. (3), in which r is the solution density (g L-1), T the absolute temperature (K), and R the universal gas constant (8.314 J mol-1 K1). DSo and DHo were determined from the intercept and slope, respectively, of the Van’t Hoff regression shown in the inset of Fig. 8.
Ke ¼
qe Ce
(3)
o
30 C o 45 C o 60 C
140 150
120 110
without Al isopropoxide addition
6.1
100
6.0
ln( Ke)
q / mg g
-1
qe / mg g
-1
130
50
5.9
5.8
5.7
100
3.0
3.1
3.2
3.3
1/T x 103 / K-1
2
3
4
5
6
Si/Al ratio in the solid Fig. 8. Ion-exchange capacity against the Si/Al ratio in the zeolitic material. C0 ¼ 389 mg Cu2þ L-1, V ¼ 40 mL; m ¼ 50 mg, and T ¼ 30 C.
0
0
100
200
300
Ce / mg L
400
500
-1
Fig. 9. Ion-exchange isotherms for HIeSi/Al-1.71. Inset: Van’t Hoff regression. V ¼ 40 mL, m ¼ 50 mg.
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Table 3 Freundlich constants and thermodynamic parameters. T (oC)
1/n
KF (mg1(1/n) g-1 L1/n)
DGo (kJ mol-1)
DHo (kJ mol-1)
DSo (J mol-1 K1)
30 45 60
0.180 0.246 0.257
52.7 33.4 28.5
15.4 15.7 15.9
10.5
16.3
Table 4 Comparison of copper adsorption parameters using different adsorbents reported in the literature. T (oC) 1/n Polyacrilonitrile nanofibers 25 Amberlite™ 252 Na 30 Phenolic resin-based carbon 25 Coal fly ash-based zeolite Y 28 Thiosemicarbazide chitosan 25 Electrospinning PVA/silica-based nanofiber 30 Coal fly ash 25 BFA zeolite 30
DGo ¼ RTlnðrKe Þ lnðrKe Þ ¼
DSo R
DHo RT
0.23 e 0.44 0.37 0.29 1.94 0.17 0.18
KF (mg1(1/n) g-1 L1/n) qmax (mg g-1) DGo (kJ mol-1) DHo (kJ mol-1) DSo (J mol-1 K1) Ref. 53.9 e 84.2 39.7 7.4 0.831 3.52 52.7
149.8 121 247 231 140.8 321.9 8.54 142
(4) (5)
The exothermic nature of the adsorption observed in Fig. 9 is confirmed by the negative enthalpies, while the spontaneous nature of the copper uptake on the zeolitic material is demonstrated by the negative values of DGo. Considering that physisorption is reported to occur in the enthalpies ranging from 2.1 to 20.9 kJ mol-1 (Belhamdi et al., 2016), the copper adsorption is likely governed by weak interactions. Furthermore, the values of DGo displayed in Table 3 are in the range commonly reported for physisorption processes (0e20.9 kJ mol-1). The positive value of DSo indicates that there is an increase of the randomness at the solid/liquid interface during the copper adsorption. Table 4 provides a comparison of the copper uptake using different adsorbents, in which qmax indicates the maximum adsorption capacity determined from the isotherms. Very high uptake capacities have been achieved using complex adsorbents, such as electrospinning PVA/silica-based nanofiber or phenolic resin-based carbon. However, besides their high cost, the adsorbent/adsorbate affinity is low, as confirmed by the highest values of 1/n shown in Table 4. Using directly coal fly ash for adsorption, for example, despite it is practically a zero-cost adsorbent, only marginal copper uptake is attained, but after converting it to zeolite (Liu et al., 2019) an expressive qmax is obtained, despite the adsorbent/ adsorbate affinity is still low. The zeolite synthesized in our work using BFA provided superior copper uptake capacity compared to the amberlite commercial resin. Although similar values of qmax have been attained using thiosemicarbazide chitosan or polyacrilonitrile nanofibers, it should be considered that the BFA zeolite has higher affinity to the adsorbate, which is an important parameter in the project of batch or column absorbers, minimizing the amount of adsorbent needed for a given copper removal. Concerning to the thermodynamic parameters, it should be noticed that the process carried out using BFA zeolite is very spontaneous (more negative DGo among the adsorbents listed in Table 4). Interestingly, the sole exothermic process was observed using BFA zeolite. 4. Conclusions Zeolite Na-A was successfully synthesized from bagasse fly-ash,
3.03 e
8.82 e
39.1 e
7.67 e e 9.12 15.4
14.4 e e 53.8 10.5
72.4 e e 0.21 16.3
Chen et al. (2019) Hirano and Gubulin (2000) Lee et al. (2015) Liu et al. (2019) Lin et al. (2017) Wang and Wang (2017) Darmayanti et al. (2017) This work
a no-cost precursor generated in large amounts in sugar mills and ethanol plants. The synthesis process proposed is clean and sustainable since it replaces the commercial chemicals containing the Al and Si sources by the BFA waste. The zeolitic materials are formed after carbon removal by calcination and submitting the assynthesized ash to a hydrothermal treatment. The ion exchange property of the as-synthesized materials was confirmed by copper uptake from aqueous solution. The addition of an extra source of Al to the synthesis medium promoted a huge and consistent enhancement of the ion exchange capacity of the zeolitic materials up to 142 mg g-1. This remarkable ion exchange capacity is much higher than the obtained using polymeric commercial resins (46.6 mg g-1) at the same temperature, adsorbent dosage, and copper concentration. Besides the excellent ion exchange properties, this material is obtained from a renewable source and gives a destination to a biomass waste generated in large amounts by an important industrial sector. Conflicts of interest The authors declare no conflict of interest. Acknowledgment J.A. Oliveira and F.A. Cunha acknowledge Coordination of Improvement of Higher Education Personnel (CAPES) and National Council for Scientific and Technological Development (CNPq), respectively, for their fellowships. References Asl, S.M.H., Javadian, H., Khavarpour, M., Belviso, C., Taghavi, M., Maghsudi, M., 2019. Porous adsorbents derived from coal fly ash as cost-effective and environmentally-friendly sources of aluminosilicate for sequestration of aqueous and gaseous pollutants: a review. J. Clean. Prod. 208, 1131e1147. https://doi.org/10.1016/j.jclepro.2018.10.186. Assawasangrat, P., Neramittagapong, S., Pranee, W., Praserthdam, P., 2016. Methanol conversion to dimethyl ether over beta zeolites derived from bagasse fly ash. Energy Sources Part A 38 (20), 3081e3088. https://doi.org/10.1080/15567036. 2015.1124945. Belhamdi, B., Merzougui, Z., Trari, M., Addoun, A., 2016. A kinetic, equilibrium and thermodynamic study of l-phenylalanine adsorption using activated carbon based on agricultural waste (date stones). J. Appl. Res. Technol. 14 (5), 354e366. https://doi.org/10.1016/j.jart.2016.08.004. Belviso, C., 2018. State-of-the-art applications of fly ash from coal and biomass: a focus on zeolite synthesis processes and issues. Prog. Energy Combust. Sci. 65, 109e135. https://doi.org/10.1016/j.pecs.2017.10.004. Chang, H.L., Shih, W.H., 2000. Synthesis of zeolites A and X from fly ashes and their
J.A. Oliveira et al. / Journal of Cleaner Production 229 (2019) 956e963 ion-exchange behavior with cobalt ions. Ind. Eng. Chem. Res. 39 (11), 4185e4191. https://doi.org/10.1021/ie990860s. Chen, C., Li, F.L., Guo, Z.H., Qu, X.Y., Wang, J.T., Zhang, J., 2019. Preparation and performance of aminated polyacrylonitrile nanofibers for highly efficient copper ion removal. Colloid. Surf. Physicochem. Eng. Asp. 568, 334e344. https:// doi.org/10.1016/j.colsurfa.2019.02.020. Dalai, A.K., Rao, M.S., Gokhale, K., 1985. Synthesis of NaX zeolite using silica from rice husk ash. Ind. Eng. Chem. Prod. Res. Dev. 24 (3), 465e468. https://doi.org/ 10.1021/i300019a026. Darmayanti, L., Notodarmodjo, S., Damanhuri, E., 2017. Removal of copper (II) ions in aqueous solutions by sorption onto fly ash. J. Eng. Technol. Sci. 49 (4), 546e559. https://doi.org/10.5614/j.eng.technol.sci.2017.49.4.9. Fungaro, D.A., Bruno, M., 2009. Removal of methylene blue from aqueous solution using zeolite synthesized from different coal fly ashes samples. Quim. Nova 32 (4), 955. U149. https://doi.org/10.1590/S0100-40422009000400024. Goscianska, J., Ptaszkowska-Koniarz, M., Frankowski, M., Franus, M., Panek, R., Franus, W., 2018. Removal of phosphate from water by lanthanum-modified zeolites obtained from fly ash. J. Colloid Interface Sci. 513, 72e81. https://doi. org/10.1016/j.jcis.2017.11.003. Gupta, V.K., Sharma, S., 2003. Removal of zinc from aqueous solutions using bagasse fly ash - a low cost adsorbent. Ind. Eng. Chem. Res. 42 (25), 6619e6624. https:// doi.org/10.1021/ie0303146. Hirano, P.C.N., Gubulin, J.C., 2000. Kinetic and thermodynamic studies on the sorption of copper ions using commercial ion-exchange resins. Brazilian Congress of Particulate Systems. In: Proceedings of the XXVII ENEMP. Campos do Jord~ ao - SP, pp. 367e372. Kim, S., Yun, Y.S., Choi, Y.E., 2018. Development of waste biomass based sorbent for removal of cyanotoxin microcystin-LR from aqueous phases. Bioresour. Technol. 247, 690e696. https://doi.org/10.1016/j.biortech.2017.09.164. Koukouzas, N., Vasilatos, C., Itskos, G.S., Moutsatsou, A., 2009. Characterization of CFB-Coal Fly Ash Zeolitic Materials and Their Potential Use in Wastewater Treatment. World of Coal Ash Conference, Lexington - KY. Lee, C.G., Jeon, J.W., Hwang, M.J., Ahn, K.H., Park, C., Choi, J.W., Lee, S.H., 2015. Lead and copper removal from aqueous solutions using carbon foam derived from phenol resin. Chemosphere 130, 59e65. https://doi.org/10.1016/j.chemosphere. 2015.02.055. Lin, C.F., Hsi, H.C., 1995. Resource recovery of waste fly-ash - synthesis of zeolite-like materials. Environ. Sci. Technol. 29 (4), 1109e1117. https://doi.org/10.1021/ es00004a033. Lin, Y.C., Wang, H.P., Gohar, F., Ullah, M.H., Zhang, X., Xie, D.F., Fang, H., Huang, J., Yang, J.X., 2017. Preparation and copper ions adsorption properties of thiosemicarbazide chitosan from squid pens. Int. J. Biol. Macromol. 95, 476e483. https://doi.org/10.1016/j.ijbiomac.2016.11.085. Liu, Y., Wang, G.D., Luo, Q., Li, X.L., Wang, Z., 2019. The thermodynamics and kinetics for the removal of copper and nickel ions by the zeolite Y synthesized from fly ash. Mater. Res. Express 6, 1e12. https://doi.org/10.1088/2053-1591/aaea41. Ma, W., Meng, F.Q., Cheng, Z.H., Xin, G., Duan, S.B., 2015. Synthesis of macroporous silica biomass nanocomposite based on XG/MgSiO3 for the removal of toxic ions. Bioresour. Technol. 186, 356e359. https://doi.org/10.1016/j.biortech.2015. 03.133. Milonji c, S.K., 2007. A consideration of the correct calculation of thermodynamic parameters of adsorption. J. Serb. Chem. Soc. 72 (12), 1363e1367. https://doi. org/10.2298/JSC0712363M. Moises, M.P., da Silva, C.T.P., Meneguin, J.G., Girotto, E.M., Radovanovic, E., 2013. Synthesis of zeolite NaA from sugarcane bagasse ash. Mater. Lett. 108, 243e246. https://doi.org/10.1016/j.matlet.2013.06.086. Moises, M.P., de Almeida, P.P., da Silva, C.T.P., Rinaldi, A.W., Girotto, E.M., Meneguin, J.G., Arroyo, P.A., Bazan, R.E., Favaro, S.L., Radovanovic, E., 2014. Synthesis of zeolite from multilayer food packing and sugar cane bagasse ash for CO2 adsorption. RSC Adv. 4 (89), 48576e48581. https://doi.org/10.1039/ c4ra04513k. Murayama, N., Yamamoto, H., Shibata, J., 2002. Mechanism of zeolite synthesis from coal fly ash by alkali hydrothermal reaction. Int. J. Miner. Process. 64 (1), 1e17. https://doi.org/10.1016/s0301-7516(01)00046-1.
963
Nibou, D., Mekatel, H., Amokrane, S., Barkat, M., Trari, M., 2010. Adsorption of Zn2þ ions onto NaA and NaX zeolites: kinetic, equilibrium and thermodynamic studies. J. Hazard Mater. 173 (1e3), 637e646. https://doi.org/10.1016/j.jhazmat. 2009.08.132. Purnomo, C.W., 2013. Utilization of bagasse fly ash for carbon-zeolite composite preparation. J. Porous Mater. 20 (5), 1305e1313. https://doi.org/10.1007/s10934013-9715-1. Purnomo, C.W., Salim, C., Hinode, H., 2012. Effect of the activation method on the properties and adsorption behavior of bagasse fly ash-based activated carbon. Fuel Process. Technol. 102, 132e139. In: https://doi.org/10.1016/j.fuproc.2012. 04.037. Querol, X., Alastuey, A., LopezSoler, A., Plana, F., Andres, J.M., Juan, R., Ferrer, P., Ruiz, C.R., 1997. A fast method for recycling fly ash: microwave-assisted zeolite synthesis. Environ. Sci. Technol. 31 (9), 2527e2533. https://doi.org/10.1021/ es960937t. Rashidi, N.A., Yusup, S., 2016. Overview on the potential of coal-based bottom ash as low-cost adsorbents. ACS Sustain. Chem. Eng. 4 (4), 1870e1884. https://doi.org/ 10.1021/acssuschemeng.5b01437. Rayalu, S., Meshram, S.U., Hasan, M.Z., 2000. Highly crystalline faujasitic zeolites from fly ash. J. Hazard Mater. 77 (1e3), 123e131. https://doi.org/10.1016/S03043894(00)00212-0. Saceda, J.J.F., de Leon, R.L., Rintramee, K., Prayoonpokarach, S., Wittayakun, J., 2011. Properties of silica from rice husk and rice husk ash and their utilization for zeolite Y synthesis. Quim. Nova 34 (8), 1394. U1289. https://doi.org/10.1590/ S0100-40422011000800018. Shah, B., Tailor, R., Shah, A., 2011a. Sorptive sequestration of 2-chlorophenol by zeolitic materials derived from bagasse fly ash. J. Chem. Technol. Biotechnol. 86 (10), 1265e1275. https://doi.org/10.1002/jctb.2646. Shah, B., Tailor, R., Shah, a.A., 2011b. Adaptation of bagasse fly ash, a sugar industry solid waste into zeolitic material for the uptake of phenol. Environ. Prog. Sustain. Energy 30 (3), 358e367. https://doi.org/10.1002/ep.10492. Shah, B.A., Patel, H.D., Shah, A.V., 2011c. Equilibrium and kinetic studies of the adsorption of basic dye from aqueous solutions by zeolite synthesized from bagasse fly ash. Environ. Prog. Sustain. Energy 30 (4), 549e557. https://doi.org/ 10.1002/ep.10505. Shah, B.A., Shah, A.V., Mistry, C.B., Tailor, R.V., Patel, H.D., 2011d. Surface modified bagasse fly ash zeolites for removal of reactive black-5. J. Dispersion Sci. Technol. 32 (9), 1247e1255. https://doi.org/10.1080/01932691.2010.505550. Shah, B., Tailor, R., Shah, A., 2012a. Equilibrium, kinetics, and breakthrough curve of phenol sorption on zeolitic material derived from BFA. J. Dispersion Sci. Technol. 33 (1e3), 41e51. https://doi.org/10.1080/01932691.2010.530079. Shah, B., Tailor, R., Shah, A., 2012b. Zeolitic bagasse fly ash as a low-cost sorbent for the sequestration of p-nitrophenol: equilibrium, kinetics, and column studies. Environ. Sci. Pollut. Res. 19 (4), 1171e1186. https://doi.org/10.1007/s11356-0110638-6. Shah, B.A., Abebe, A.A., Shah, A.V., 2017a. Microwave-synthesized bariumimpregnated siliceous zeolitic material derived from bagasse fly ash for uptake of aniline. Arabian J. Sci. Eng. 42 (1), 139e152. https://doi.org/10.1007/ s13369-016-2083-9. Shah, B.A., Pandya, D.D., Shah, H.A., 2017b. Impounding of ortho-chlorophenol by zeolitic materials adapted from bagasse fly ash: four factor three level BoxBehnken design modelling and optimization. Arabian J. Sci. Eng. 42 (1), 241e260. https://doi.org/10.1007/s13369-016-2294-0. Singer, A., Berkgaut, V., 1995. Cation exchange properties of hydrothermally treated coal fly ash. Environ. Sci. Technol. 29 (7), 1748e1753. https://doi.org/10.1021/ es00007a009. Volli, V., Purkait, M.K., 2015. Selective preparation of zeolite X and A from fly ash and its use as catalyst for biodiesel production. J. Hazard Mater. 297, 101e111. https://doi.org/10.1016/j.jhazmat.2015.04.066. Wang, D.D., Wang, J.N., 2017. Electrospinning Polyvinyl alcohol/silica-based nanofiber as highly efficient adsorbent for simultaneous and sequential removal of Bisphenol A and Cu(II) from water. Chem. Eng. J. 314, 714e726. https://doi.org/ 10.1016/j.cej.2016.12.037.
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Synthesis of zeolite from sugarcane bagasse fly ash and its application as a low-cost adsorbent to remove heavy metals ssica A. Oliveira, Felipe A. Cunha, Luís A.M. Ruotolo* Je ~o Carlos, Rod. Washington Luiz km 235, 13565-905, Sa ~o Carlos, SP, Brazil Department of Chemical Engineering, Federal University of Sa
a r t i c l e i n f o
a b s t r a c t
Article history: Received 8 January 2019 Received in revised form 17 April 2019 Accepted 7 May 2019 Available online 7 May 2019
A new clean and sustainable procedure to synthesize low-cost zeolites from sugarcane bagasse fly ash (BFA), an industrial waste, is presented. BFA is used as source of Al and Si to obtain aluminosilicates with distinguished ion exchange capacity, confirmed by copper uptake. After the fly ash has been calcined and submitted to hydrothermal treatment employing NaOH as mineralizing agent, the XRD patterns of the as-synthesized samples revealed the formation of zeolite Na-A. Temperature and calcination time are key parameters affecting the ion-exchange capacity (q) of the zeolitic materials. Calcination at 600 C for 8 h, under oxygen atmosphere, ensures that all carbon from fly ash has been removed and optimizes the ionexchange properties. As a strategy to further improve q, Al isopropoxide was added to the synthesis medium, reducing the Si/Al ratio in the zeolite and generating more ion exchange sites. The hydrothermal treatment and addition of Al modify the structure and morphology of the zeolitic material, leading to a maximized adsorption capacity (142 mg Cu2þ g-1) at 1.71 Si/Al, which is much higher than the observed for a commercial polymeric resin (46.6 mg g-1). © 2019 Elsevier Ltd. All rights reserved.
Keywords: Na-A Sugarcane bagasse fly ash Adsorbent Ion-exchange Heavy metal
1. Introduction The synthesis of zeolites using biowaste as source of Al and Si has been investigated by many authors in the last few years (Belviso, 2018; Ma et al., 2015). Among the numerous applications of zeolites, their use as cation exchangers for effluent treatment or metal removal is well known. Zeolites are crystalline aluminosilicates with three-dimensional structures formed by tetrahedrons composed by Si and Al bounded by oxygen atoms. The presence of Al3þ in the zeolite framework results in a negative net charge neutralized by compensation cations, which are responsible by the ion exchange property of these materials. Additionally, the microporous structure with well-defined size cavities, besides the high surface area, also provides selectivity, adsorption, and catalytic properties (Nibou et al., 2010). In the last few decades, the use of inorganic (Asl et al., 2019; Rashidi and Yusup, 2016) and biomass wastes (Kim et al., 2018) have been reported as precursors for the synthesis of zeolitic materials (Belviso, 2018). A typical example is the use of coal fly ash from coal-fired thermal power plants to synthesize zeolite A
* Corresponding author. E-mail address: [email protected] (L.A.M. Ruotolo). https://doi.org/10.1016/j.jclepro.2019.05.069 0959-6526/© 2019 Elsevier Ltd. All rights reserved.
(Goscianska et al., 2018), X, faujasite-type (Chang and Shih, 2000; Volli and Purkait, 2015), beta (Assawasangrat et al., 2016), Y (Rayalu et al., 2000), erionite ZSM-18, linde (Koukouzas et al., 2009), F linde, kalsilite, philipsite-KM (Querol et al., 1997), analcite, hydroxy sodalite (Lin and Hsi, 1995), and P (Fungaro and Bruno, 2009; Murayama et al., 2002). Among the biomass precursors, fast kinetics and high removal capacity have been reported for zeolites synthesized using rice husk as source of Al and Si (Dalai et al., 1985; Saceda et al., 2011). Despite this plethora, reports on zeolites synthesis from bagasse fly ash are still scarce in literature. The sugarcane bagasse fly ash (BFA) is produced in large amounts in sugar and ethanol plants after burning biomass to generate power and steam and results from the incomplete burn of the bagasse. Hence, finding a cleaner process to add value and give a final destination to this solid waste is of great interest from the environmental and economic point of view. Since BFA is mainly composed by unburned carbon, SiO2 and Al2O3 (Gupta and Sharma, 2003), here we studied the conversion of this waste into aluminosilicates to obtain a low-cost ion exchange materials. According to Shah et al., zeolite P and analcime are the main zeolitic material obtained after the hydrothermal treatment of the as-received BFA; their uptake capacity was confirmed towards 2chlorophenol (Shah et al., 2011a), phenol (Shah et al., 2011b, 2012a), dye (Shah et al., 2011c, 2011d), and p-nitrophenol (Shah
J.A. Oliveira et al. / Journal of Cleaner Production 229 (2019) 956e963
et al., 2012b) adsorption in batch and column. Purnomo (2013) extracted the silicon and aluminum from bagasse fly ash to synthetize Na-X and Na-A zeolites. In this process, Si and Al were separated from carbon by mixing the fly ash with NaOH, followed by heating at 500 C and then washing the resulting fused material with deionized water to obtain Si and Al ions. Na-A zeolite was also obtained by Moises et al., 2013, 2014, but instead of BFA, the bagasse bottom ash was used as primary source of Al and Si. Recently, Shah et al., 2017a, 2017b reported the preparation of zeolitic materials employing microwave hydrothermal treatment and their application to o-chlorophenol and aniline adsorption. In these works, BFA is used directly to obtain the zeolites or complicated procedures are utilized to extract the Si and Al. Differently, to the best of our knowledge, here we report for the first time the synthesis of zeolites using the BFA ash obtained after thermal treatment to remove the unburned carbon. Furthermore, only few authors explored the ion exchange properties of the zeolites prepared from low-cost sources to remove heavy metals. In this work we investigated the use of BFA as source of Si and Al to obtain low-cost zeolitic materials with distinguished cation exchange properties. The new procedure employed to obtain zeolites is clean and sustainable since it replaces, totally or partially, the usual Si and Al precursors (tetraethyl orthosilicate and aluminum isopropoxide, respectively) by an abundant source of these elements present in BFA. Different temperature and calcination time are investigated to remove the remaining carbon in BFA and increase the Si and Al content. To further improve the ion exchange capacity, we also investigate the effect of reducing the Si/Al ratio by adding Al isopropoxide in the gel synthesis. As far as we know, this procedure has not been reported before for synthesis of zeolitic materials using BFA. The ion exchange capacity of the assynthetized materials is investigated towards Cu2þ uptake. Copper was chosen because of the large volume of effluents generated in many industrial processes, which is commonly removed by ion exchange using expensive polymeric resins.
957
2. Experimental 2.1. Materials BFA was collected at the exit of a gas washing tower from a sugar mill and ethanol plant. After washing, the fly ash was calcined at different temperatures under O2 atmosphere in order to obtain the ash, mostly composed by Si and Al (Gupta and Sharma, 2003). The ash was submitted to hydrothermal treatment in the presence of 3.5 mol L-1 NaOH (Sigma-Aldrich) to obtain the zeolitic material. In some experiments, aluminum isopropoxide, C9H21O3Al (SigmaAldrich), was added to the synthesis medium. CuSO4.5H2O (Synth) was used as source of Cu2þ in the ion exchange experiments. All solutions were prepared using deionized water. 2.2. Zeolite synthesis The BFA was previously separated from sand and other contaminants by flotation, dried in an oven at 100 C, grinded and sieved. The particles with diameters lower than 38 mm were calcined in a furnace (EDG 7000), under O2 atmosphere, at different temperature and calcination time. The as-obtained ash was submitted to hydrothermal synthesis applying the conditions described in Table 1 and illustrated in Fig. 1. The reaction vessel is a PTFE lined autoclave. After 24 h, the material was washed with deionized water until constant pH, filtered, and dried at 60 C for 24 h. The samples were coded according to the treatment procedure, temperature, and calcination time, respectively; e.g. H-600-8 indicates that the material was synthesized according to procedure H using the ash obtained after fly ash calcination at 600 C for 8 h. In the case in which Al isopropoxide was added to synthesis gel, the ash C-600-8 was used in all experiments and the samples were labeled according to the Si/Al ratio in the solid phase, e.g. HIeSi/Al1.71.
Table 1 Procedures employed for the treatment of BFA. Procedure
Description
C H HI
BFA was only calcined employing different temperatures and times Calcination followed by hydrothermal reaction in autoclave containing 3.5 mol L-1 NaOH and maintained in an oven at 100 C, for 24 h Similar to procedure H, but adding Al isopropoxide
Fig. 1. Schematic representation of the zeolite synthesis.
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2.3. Characterization Thermogravimetric analysis (Mettler Toledo TGA/SDTA851e) was performed at room temperature, using a heating rate of 15 C min1 in nitrogen and oxygen (60 mL min1). The phase composition was determined from X-ray diffraction (XRD) recorded on a Siemens D5005 diffractometer using a Ni-filtered Cu Ka radiation (l ¼ 1.5418 Å) in a 2q range between 5 and 65 at 2 min-1. Search Match software was used to index the crystallographic phase. SEM images were obtained in a Philips XL30 FEG microscope. The X-ray fluorescence (XRF) analysis was performed in an EDX 720 Shimadzu in dispersive energy mode. The zeta potential was measured for different values of pH using a Zetasizer Nano ZS system (Malvern Instruments). The Si and Al content in C-600-8 was determined by inductively coupled plasma optical emission spectrometry (ICP-OES) using a Thermo Scientific iCAP6000.
Residual mass / W W0-1
1.0 0.8 0.6
BFA - N2 BFA - O2
0.4 0.2 0.0
200
400
(a)
q¼
V ðC0 CÞ ms
(1)
The influence of pH on the ion-exchange was studied employing the same procedure, but contacting 50 mg of adsorbent with 40 mL of 93.0 mg L-1 Cu2þ solution with values of pH varying from 1.0 to 4.5 (adjusted using sulfuric acid). The concentrations of Cu2þ were established considering the values commonly found in industrial effluents treated by adsorption. The isotherms were obtained following the same procedure described before, but contacting 50 mg of adsorbent with different concentrations of Cu2þ (50 mL). A Dubnoff shaking water bath was used to control the temperature in these experiments. 3. Results and discussion 3.1. Effect of calcination Fig. 2a shows the thermogravimetric curves for BFA recorded in N2 and O2 atmospheres. Under oxygen, the weight loss observed until 200 C is ascribed to water removal, while the weight loss in the range between 350 and 580 C regards to the burn of carbon and organic residues, which are completely eliminated at ~900 C (87% weight loss), remaining only the inorganic compounds. On the other hand, under N2, the remaining mass is composed by carbon and inorganics. Hence, according to the mass balance, the BFA composition is estimated as 7.1% water, 17.5% volatiles, 62.4% fixed carbon, and 13.0% ash. Taking into account the results from Fig. 2a, different calcination temperatures were applied to determine the desired operational time to eliminate the remaining carbon from the fly ash (Fig. 2b). The normalized weight loss was defined as the ratio between the weight loss after calcination and the ash content determined in the
1000
1200
1400
100
Normalized weight loss / %
800
Temperature / °C
2.4. Ion exchange Ion exchange experiments were carried out to determine the ion-exchange capacity (q) as a function of the calcination and synthesis conditions. Erlenmeyers (125 mL), containing 50 mg of zeolite and 50 mL of Cu2þ solution, were submitted to orbital shaking at 150 rpm for 24 h in order to achieve the equilibrium. The solid phase was separated by centrifugation and the copper remained in the liquid phase was measured by atomic absorption spectrophotometry (Varian, model SpectrAA200). The copper concentration in the solid phase (q) was determined using Equation (1), in which V is the volume (L), ms mass of the adsorbent (g), Co the initial copper concentration (mg L-1), and C the copper concentration at equilibrium (mg L-1).
600
o
600 C o 800 C
80
60
40
20
0
0 10 min
(b)
1 h1
2 h2
3 h3
4 h4
5 h5
Calcination time
Fig. 2. (a) Thermogravimetric (TG) analyses of BFA in N2 and O2 atmospheres and (b) normalized weight loss as a function of time and calcination temperature (under oxygen atmosphere).
TG analysis, i.e., 13% w/w of the BFA mass. According to Fig. 2b, after applying 800 C (5 h), all carbon and volatiles are eliminated, resulting in a white ash containing Si and Al, among small fractions of other elements. Fig. 2b reveals that 4 h calcination at 600 C practically remove water and organic volatiles (~98%), while applying 800 C the maximum weight loss is achieved after 3 h. Although the faster kinetics, calcination at 800 C modifies the morphology and has deleterious effects on the ion exchange capacity of the synthesized zeolites. 3.2. Characterizations 3.2.1. Morphological and structural analysis Fig. 3 shows the SEM images of the samples submitted to calcination and hydrothermal treatment. After the bagasse burning, the BFA retains the morphological aspect of the precursor (Fig. 3a), which is not preserved after calcination. Although the ash does not exhibit a specific morphology (Fig. 3b), after the hydrothermal treatment it is converted to spherical particles, with diameters varying from 2 to 5 mm (Fig. 3c), containing the zeolitic material
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959
Fig. 3. SEM images: (a) fly-ash, (b) C-600-4, (c)e(d) H-600-4, (e) H-600-8, and (f) H-800-4.
(Fig. 3d) similar to the obtained by authors using coal fly ash (Koukouzas et al., 2009; Singer and Berkgaut, 1995). The cenosphere morphology has been attributed to the presence of residual carbon, as in the case of C600-4. This is corroborated by the fact that after the hydrothermal treatment of C-600-8 (in which there is no residual carbon), cenospheres are not formed (Fig. 3e) and the resulting material has a distinct morphology (Fig. 3f). The XRD pattern of the fly ash shown in Fig. 4a confirms the
-SiO2 Zeolite Na-A H-800-4
Intensity / a.u.
H-800-4
H-600-4
Intensity / a.u.
H-600-4
C-600-4
C-600-4
fly ash
fly ash 0
(a)
10
20
30
40
2 / degree
50
60
70
22 23 24 25 26
(b)
28 30 32 34 36
2 / degree
Fig. 4. XRD patterns: (a) 5 2q 65 and (b) 22 2q 36 .
presence of Si as a-SiO2 (quartz low) (JCPDS 86e1628). The broad peak regards to the existence of disordered microcrystalline carbonized material with small amounts of amorphous phase of silica and/or alumina. After calcination and hydrothermal treatment, this broad peak disappears since most of the carbon has been removed. For samples C-600-4 and H-600-4, the a-SiO2 peaks persist and are even more intense, indicating that the resulting material presents more crystalline silica. On the other hand, the relative intensity of the secondary peaks for H-800-4 decreases, revealing that higher calcination temperatures affect not only the morphology (Fig. 3), but the crystallinity as well. Furthermore, after the hydrothermal treatment, new XRD peaks (Fig. 4b) reveals the synthesis of the Na-A zeolite (JCPDS 73e2340). Al isopropoxide was added to the synthesis medium as an attempt to decrease the Si/Al ratio and further improve the ion exchange properties. Prior these syntheses, the amount of Si and Al in C-600-8 was determined by ICP-OES, revealing the presence of 49 mg Al and 335 mg Si per gram of ash (Si/Al ¼ 6.8). The BFA composition was determined by mass balance using the percentages determined from the TG analysis (Fig. 2), giving 50 mg water, 124 mg volatiles, 442 mg fixed carbon and 384 mg ash per gram of BFA. Table 2 shows the Si/Al ratios in the synthesis medium and in the zeolitic material, determined by XRF. The samples were labeled as HIeSi/Al- followed by the Si/Al ratio in the solid. XRD patterns shown in Fig. 5a for the materials containing different Si/Al ratios follow the same trend observed in Fig. 4 and are mainly composed by a-SiO2 and Na-A zeolite. The HI-samples have similar structures with two weak peaks at 52 and 62
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60
Table 2 Si/Al ratio in the synthesis medium and in the zeolitic material. Si/Al (synthesis medium)
Si/Al (zeolitic material)x
HIeSi/Al-1.61 HIeSi/Al-1.71 HIeSi/Al-1.82 HIeSi/Al-2.04 HIeSi/Al-2.64 HIeSi/Al-3.83 H-600-8
1.3 2.0 2.3 3.0 3.8 5.1 6.8±
1.61 1.71 1.82 2.04 2.64 3.83 5.90
50
q / mg g
-1
Sample
The Si source is the C-600-8 and the Al sources are C-600-8 (49 mg Al g-1) and Al isopropoxide (27 mg Al g-1). ±Determined by ICP. xDetermined by XRF.
40
Zeta potential / mV
960
30 20 10 0 -10 -20
30
3
4
5
6
7
pH
20 10
attributed to Al2O3 (JCPDS 88e0107), revealing that part of the Al precipitates as oxide. Interestingly, H-600-8 presents more intense zeolite peaks than H-600-4, suggesting that longer calcination improves the zeolite crystallinity. The SEM images for HIeSi/Al-1.71 (Fig. 5bec) reveal a remarkable morphology change when the hydrothermal treatment is carried out in the presence of Al-isopropoxide. The rod-type shape of the particles is ~400 nm long (Fig. 5c), whose agglomerates form large sponge-like clusters (Fig. 5b). This same morphology is observed for HIeSi/Al-1.61, but disappear for Si/Al ratios higher than 1.82.
0 1
3
Fig. 6. Copper uptake and zeta potential (inset) as a function of pH. C0 ¼ 93 mg Cu2þ L, m ¼ 50 mg H-600-4, T ¼ 30 C.
precipitates after the addition of the aluminosilicate. Considering that the natural pH of the copper solutions is close to 4.5, this pH was employed in the next experiments. Fig. 7a shows the values of q for copper removal using the asreceived fly ash, the calcined fly ash, and the ash submitted to hydrothermal treatments. The low copper uptake for fly ash (Gupta and Sharma, 2003) and the calcined samples was already expected, but it is interesting to note how calcination at 800 C decreases q, even after the hydrothermal treatment, suggesting that the crystallinity loss observed in the XRD pattern (Fig. 4a) and the morphology change (Fig. 3a) have a deleterious effect on the ionexchange properties of these materials. The superior ion exchange performance of the materials
HI-Si/Al-3.83
Intensity / a.u.
HI-Si/Al-2.64 HI-Si/Al-2.04
HI-Si/Al-1.82 HI-Si/Al-1.71 HI-Si/Al-1.61 H-600-8 (Si/Al = 5.90)
(a)
10
20
30
40
50
60
5
1
As the pH affects the properties of the exchangeable ions and the surface charge of the solid phase, its influence on the ion exchange capacity was prior investigated. According to Fig. 6, the absence of adsorption at pH lower than 2.5 is attributed to the excess of protons that hinders the copper uptake due to the strong competition between Hþ and Cu2þ. As the pH approaches the isoelectric point at pH ~6.0 (inset Fig. 6), the copper uptake grows up to its maximum at 4.5. For pH higher than 4.5, copper immediately
0
4
pH
3.3. Cu2þ sorption
-SiO2 Zeolite Na-A Al2O3
2
70
2 / degree
Fig. 5. (a) XRD patterns for the samples with different Si/Al ratios; (bec) SEM images of HIeSi/Al-1.71: (b) 7500X and (c) 100000X.
00-3
H-800-4
C-80 0-4 C-800-5
00-3
sh
10
961
known (Chang and Shih, 2000; Purnomo et al., 2012). It is interesting to note the ion exchange capacity of HIeSi/Al-1.61 decreases, indicating that, despite the higher content of Al in the sample, likely it is not associated to the Na-A. Comparing the maximum ion exchange capacity obtained using HIeSi/Al-1.71 (142 mg g-1) with the obtained by Hirano and Gubulin (2000) using commercial polymeric resins (46.6 mg g-1) at the same temperature, material dosage, and copper concentration, it is evident the superior performance of the zeolitic material.
C-6 C-8
20
C-6
30
00-4
40
00-5 C-6 00-8
50
Fly a
qe / mg g
-1
60
H-8
H-6
00 - 4
70
H-6
80
00-5 H- 6 00 -8
J.A. Oliveira et al. / Journal of Cleaner Production 229 (2019) 956e963
3.4. Thermodynamics
0
Samples Fig. 7. Ion-exchange capacity of the different materials. C0 ¼ 82.7 mg Cu2þ L-1, m ¼ 50 mg, T ¼ 30 C.
obtained after hydrothermal treatment using the ash calcined at 600 C is ascribed to the formation of the Na-A zeolite. The lower values of q observed for the samples calcined for 4 and 5 h indicate that the presence of residual carbon, besides promoting the cenosphere morphology (Fig. 2b), also affects the ion exchange. Once removed the carbon, the ion exchange capacity reaches its maximum for HI-600-8. Therefore, the ash C-600-8 was chosen as precursor to investigate the hydrothermal synthesis varying the Si/ Al ratio. It is well known that the ion exchange property of aluminosilicates depends on the number of Al atoms in their structure, responsible for the negative charge in the zeolite framework, which is compensated by a cation, as schematized in the inset of Fig. 8. Therefore, the addition of Al in the synthesis medium was tested as a strategy to further improve the values of q. According to Fig. 8, the trend of Si/Al on the values of ion exchange capacity is more intensely manifested for values lower than 2.04, when large amounts of Al-isopropoxide is employed and alumina has been formed (Fig. 5a). The improved ion exchange capacity of these samples indicates that more Al atoms have been incorporated into the zeolitic material, providing negative charges which are compensated by Naþ from the synthesis medium. Moreover, the high cation exchange capacity of zeolite Na-A is well
According to the IUPAC classification, the type I isotherms shown in Fig. 9 for the copper uptake using HIeSi/Al-1.71 indicates that the sorbent has strong affinity for cations. The sorption data are best fitted to the Freundlich isotherm (Eq. (2)), suggesting that adsorption occurs in multilayers on a heterogeneous surface. In Eq. (2), Ce is the solute concentration in the liquid phase at equilibrium (mg L-1), 1/n is a dimensionless constant related to the surface heterogeneity, and KF is the Freundlich constant, related to the adsorption capacity (mg1(1/n) g-1 L1/n). The Freundlich constants and thermodynamic parameters are shown in Table 3 for three different temperatures. It is evident the detrimental effect of temperature on the adsorption process since KF decreases and 1/n increases, indicating less favorable isotherms. Considering that the higher 1/n the lowest the adsorbent/adsorbate affinity, lower values of 1/n are desirable in order to obtain better adsorption performances. 1=n
qe ¼ KF C e
(2)
The changes in free energy (DGo), enthalpy (DHo), and entropy (DSo) were calculated according to Eqs. (4)and (5), proposed by Milonji c (2007). The equilibrium constants (Ke), in L g-1, were calculated by Eq. (3), in which r is the solution density (g L-1), T the absolute temperature (K), and R the universal gas constant (8.314 J mol-1 K1). DSo and DHo were determined from the intercept and slope, respectively, of the Van’t Hoff regression shown in the inset of Fig. 8.
Ke ¼
qe Ce
(3)
o
30 C o 45 C o 60 C
140 150
120 110
without Al isopropoxide addition
6.1
100
6.0
ln( Ke)
q / mg g
-1
qe / mg g
-1
130
50
5.9
5.8
5.7
100
3.0
3.1
3.2
3.3
1/T x 103 / K-1
2
3
4
5
6
Si/Al ratio in the solid Fig. 8. Ion-exchange capacity against the Si/Al ratio in the zeolitic material. C0 ¼ 389 mg Cu2þ L-1, V ¼ 40 mL; m ¼ 50 mg, and T ¼ 30 C.
0
0
100
200
300
Ce / mg L
400
500
-1
Fig. 9. Ion-exchange isotherms for HIeSi/Al-1.71. Inset: Van’t Hoff regression. V ¼ 40 mL, m ¼ 50 mg.
962
J.A. Oliveira et al. / Journal of Cleaner Production 229 (2019) 956e963
Table 3 Freundlich constants and thermodynamic parameters. T (oC)
1/n
KF (mg1(1/n) g-1 L1/n)
DGo (kJ mol-1)
DHo (kJ mol-1)
DSo (J mol-1 K1)
30 45 60
0.180 0.246 0.257
52.7 33.4 28.5
15.4 15.7 15.9
10.5
16.3
Table 4 Comparison of copper adsorption parameters using different adsorbents reported in the literature. T (oC) 1/n Polyacrilonitrile nanofibers 25 Amberlite™ 252 Na 30 Phenolic resin-based carbon 25 Coal fly ash-based zeolite Y 28 Thiosemicarbazide chitosan 25 Electrospinning PVA/silica-based nanofiber 30 Coal fly ash 25 BFA zeolite 30
DGo ¼ RTlnðrKe Þ lnðrKe Þ ¼
DSo R
DHo RT
0.23 e 0.44 0.37 0.29 1.94 0.17 0.18
KF (mg1(1/n) g-1 L1/n) qmax (mg g-1) DGo (kJ mol-1) DHo (kJ mol-1) DSo (J mol-1 K1) Ref. 53.9 e 84.2 39.7 7.4 0.831 3.52 52.7
149.8 121 247 231 140.8 321.9 8.54 142
(4) (5)
The exothermic nature of the adsorption observed in Fig. 9 is confirmed by the negative enthalpies, while the spontaneous nature of the copper uptake on the zeolitic material is demonstrated by the negative values of DGo. Considering that physisorption is reported to occur in the enthalpies ranging from 2.1 to 20.9 kJ mol-1 (Belhamdi et al., 2016), the copper adsorption is likely governed by weak interactions. Furthermore, the values of DGo displayed in Table 3 are in the range commonly reported for physisorption processes (0e20.9 kJ mol-1). The positive value of DSo indicates that there is an increase of the randomness at the solid/liquid interface during the copper adsorption. Table 4 provides a comparison of the copper uptake using different adsorbents, in which qmax indicates the maximum adsorption capacity determined from the isotherms. Very high uptake capacities have been achieved using complex adsorbents, such as electrospinning PVA/silica-based nanofiber or phenolic resin-based carbon. However, besides their high cost, the adsorbent/adsorbate affinity is low, as confirmed by the highest values of 1/n shown in Table 4. Using directly coal fly ash for adsorption, for example, despite it is practically a zero-cost adsorbent, only marginal copper uptake is attained, but after converting it to zeolite (Liu et al., 2019) an expressive qmax is obtained, despite the adsorbent/ adsorbate affinity is still low. The zeolite synthesized in our work using BFA provided superior copper uptake capacity compared to the amberlite commercial resin. Although similar values of qmax have been attained using thiosemicarbazide chitosan or polyacrilonitrile nanofibers, it should be considered that the BFA zeolite has higher affinity to the adsorbate, which is an important parameter in the project of batch or column absorbers, minimizing the amount of adsorbent needed for a given copper removal. Concerning to the thermodynamic parameters, it should be noticed that the process carried out using BFA zeolite is very spontaneous (more negative DGo among the adsorbents listed in Table 4). Interestingly, the sole exothermic process was observed using BFA zeolite. 4. Conclusions Zeolite Na-A was successfully synthesized from bagasse fly-ash,
3.03 e
8.82 e
39.1 e
7.67 e e 9.12 15.4
14.4 e e 53.8 10.5
72.4 e e 0.21 16.3
Chen et al. (2019) Hirano and Gubulin (2000) Lee et al. (2015) Liu et al. (2019) Lin et al. (2017) Wang and Wang (2017) Darmayanti et al. (2017) This work
a no-cost precursor generated in large amounts in sugar mills and ethanol plants. The synthesis process proposed is clean and sustainable since it replaces the commercial chemicals containing the Al and Si sources by the BFA waste. The zeolitic materials are formed after carbon removal by calcination and submitting the assynthesized ash to a hydrothermal treatment. The ion exchange property of the as-synthesized materials was confirmed by copper uptake from aqueous solution. The addition of an extra source of Al to the synthesis medium promoted a huge and consistent enhancement of the ion exchange capacity of the zeolitic materials up to 142 mg g-1. This remarkable ion exchange capacity is much higher than the obtained using polymeric commercial resins (46.6 mg g-1) at the same temperature, adsorbent dosage, and copper concentration. Besides the excellent ion exchange properties, this material is obtained from a renewable source and gives a destination to a biomass waste generated in large amounts by an important industrial sector. Conflicts of interest The authors declare no conflict of interest. Acknowledgment J.A. Oliveira and F.A. Cunha acknowledge Coordination of Improvement of Higher Education Personnel (CAPES) and National Council for Scientific and Technological Development (CNPq), respectively, for their fellowships. References Asl, S.M.H., Javadian, H., Khavarpour, M., Belviso, C., Taghavi, M., Maghsudi, M., 2019. Porous adsorbents derived from coal fly ash as cost-effective and environmentally-friendly sources of aluminosilicate for sequestration of aqueous and gaseous pollutants: a review. J. Clean. Prod. 208, 1131e1147. https://doi.org/10.1016/j.jclepro.2018.10.186. Assawasangrat, P., Neramittagapong, S., Pranee, W., Praserthdam, P., 2016. Methanol conversion to dimethyl ether over beta zeolites derived from bagasse fly ash. Energy Sources Part A 38 (20), 3081e3088. https://doi.org/10.1080/15567036. 2015.1124945. Belhamdi, B., Merzougui, Z., Trari, M., Addoun, A., 2016. A kinetic, equilibrium and thermodynamic study of l-phenylalanine adsorption using activated carbon based on agricultural waste (date stones). J. Appl. Res. Technol. 14 (5), 354e366. https://doi.org/10.1016/j.jart.2016.08.004. Belviso, C., 2018. State-of-the-art applications of fly ash from coal and biomass: a focus on zeolite synthesis processes and issues. Prog. Energy Combust. Sci. 65, 109e135. https://doi.org/10.1016/j.pecs.2017.10.004. Chang, H.L., Shih, W.H., 2000. Synthesis of zeolites A and X from fly ashes and their
J.A. Oliveira et al. / Journal of Cleaner Production 229 (2019) 956e963 ion-exchange behavior with cobalt ions. Ind. Eng. Chem. Res. 39 (11), 4185e4191. https://doi.org/10.1021/ie990860s. Chen, C., Li, F.L., Guo, Z.H., Qu, X.Y., Wang, J.T., Zhang, J., 2019. Preparation and performance of aminated polyacrylonitrile nanofibers for highly efficient copper ion removal. Colloid. Surf. Physicochem. Eng. Asp. 568, 334e344. https:// doi.org/10.1016/j.colsurfa.2019.02.020. Dalai, A.K., Rao, M.S., Gokhale, K., 1985. Synthesis of NaX zeolite using silica from rice husk ash. Ind. Eng. Chem. Prod. Res. Dev. 24 (3), 465e468. https://doi.org/ 10.1021/i300019a026. Darmayanti, L., Notodarmodjo, S., Damanhuri, E., 2017. Removal of copper (II) ions in aqueous solutions by sorption onto fly ash. J. Eng. Technol. Sci. 49 (4), 546e559. https://doi.org/10.5614/j.eng.technol.sci.2017.49.4.9. Fungaro, D.A., Bruno, M., 2009. Removal of methylene blue from aqueous solution using zeolite synthesized from different coal fly ashes samples. Quim. Nova 32 (4), 955. U149. https://doi.org/10.1590/S0100-40422009000400024. Goscianska, J., Ptaszkowska-Koniarz, M., Frankowski, M., Franus, M., Panek, R., Franus, W., 2018. Removal of phosphate from water by lanthanum-modified zeolites obtained from fly ash. J. Colloid Interface Sci. 513, 72e81. https://doi. org/10.1016/j.jcis.2017.11.003. Gupta, V.K., Sharma, S., 2003. Removal of zinc from aqueous solutions using bagasse fly ash - a low cost adsorbent. Ind. Eng. Chem. Res. 42 (25), 6619e6624. https:// doi.org/10.1021/ie0303146. Hirano, P.C.N., Gubulin, J.C., 2000. Kinetic and thermodynamic studies on the sorption of copper ions using commercial ion-exchange resins. Brazilian Congress of Particulate Systems. In: Proceedings of the XXVII ENEMP. Campos do Jord~ ao - SP, pp. 367e372. Kim, S., Yun, Y.S., Choi, Y.E., 2018. Development of waste biomass based sorbent for removal of cyanotoxin microcystin-LR from aqueous phases. Bioresour. Technol. 247, 690e696. https://doi.org/10.1016/j.biortech.2017.09.164. Koukouzas, N., Vasilatos, C., Itskos, G.S., Moutsatsou, A., 2009. Characterization of CFB-Coal Fly Ash Zeolitic Materials and Their Potential Use in Wastewater Treatment. World of Coal Ash Conference, Lexington - KY. Lee, C.G., Jeon, J.W., Hwang, M.J., Ahn, K.H., Park, C., Choi, J.W., Lee, S.H., 2015. Lead and copper removal from aqueous solutions using carbon foam derived from phenol resin. Chemosphere 130, 59e65. https://doi.org/10.1016/j.chemosphere. 2015.02.055. Lin, C.F., Hsi, H.C., 1995. Resource recovery of waste fly-ash - synthesis of zeolite-like materials. Environ. Sci. Technol. 29 (4), 1109e1117. https://doi.org/10.1021/ es00004a033. Lin, Y.C., Wang, H.P., Gohar, F., Ullah, M.H., Zhang, X., Xie, D.F., Fang, H., Huang, J., Yang, J.X., 2017. Preparation and copper ions adsorption properties of thiosemicarbazide chitosan from squid pens. Int. J. Biol. Macromol. 95, 476e483. https://doi.org/10.1016/j.ijbiomac.2016.11.085. Liu, Y., Wang, G.D., Luo, Q., Li, X.L., Wang, Z., 2019. The thermodynamics and kinetics for the removal of copper and nickel ions by the zeolite Y synthesized from fly ash. Mater. Res. Express 6, 1e12. https://doi.org/10.1088/2053-1591/aaea41. Ma, W., Meng, F.Q., Cheng, Z.H., Xin, G., Duan, S.B., 2015. Synthesis of macroporous silica biomass nanocomposite based on XG/MgSiO3 for the removal of toxic ions. Bioresour. Technol. 186, 356e359. https://doi.org/10.1016/j.biortech.2015. 03.133. Milonji c, S.K., 2007. A consideration of the correct calculation of thermodynamic parameters of adsorption. J. Serb. Chem. Soc. 72 (12), 1363e1367. https://doi. org/10.2298/JSC0712363M. Moises, M.P., da Silva, C.T.P., Meneguin, J.G., Girotto, E.M., Radovanovic, E., 2013. Synthesis of zeolite NaA from sugarcane bagasse ash. Mater. Lett. 108, 243e246. https://doi.org/10.1016/j.matlet.2013.06.086. Moises, M.P., de Almeida, P.P., da Silva, C.T.P., Rinaldi, A.W., Girotto, E.M., Meneguin, J.G., Arroyo, P.A., Bazan, R.E., Favaro, S.L., Radovanovic, E., 2014. Synthesis of zeolite from multilayer food packing and sugar cane bagasse ash for CO2 adsorption. RSC Adv. 4 (89), 48576e48581. https://doi.org/10.1039/ c4ra04513k. Murayama, N., Yamamoto, H., Shibata, J., 2002. Mechanism of zeolite synthesis from coal fly ash by alkali hydrothermal reaction. Int. J. Miner. Process. 64 (1), 1e17. https://doi.org/10.1016/s0301-7516(01)00046-1.
963
Nibou, D., Mekatel, H., Amokrane, S., Barkat, M., Trari, M., 2010. Adsorption of Zn2þ ions onto NaA and NaX zeolites: kinetic, equilibrium and thermodynamic studies. J. Hazard Mater. 173 (1e3), 637e646. https://doi.org/10.1016/j.jhazmat. 2009.08.132. Purnomo, C.W., 2013. Utilization of bagasse fly ash for carbon-zeolite composite preparation. J. Porous Mater. 20 (5), 1305e1313. https://doi.org/10.1007/s10934013-9715-1. Purnomo, C.W., Salim, C., Hinode, H., 2012. Effect of the activation method on the properties and adsorption behavior of bagasse fly ash-based activated carbon. Fuel Process. Technol. 102, 132e139. In: https://doi.org/10.1016/j.fuproc.2012. 04.037. Querol, X., Alastuey, A., LopezSoler, A., Plana, F., Andres, J.M., Juan, R., Ferrer, P., Ruiz, C.R., 1997. A fast method for recycling fly ash: microwave-assisted zeolite synthesis. Environ. Sci. Technol. 31 (9), 2527e2533. https://doi.org/10.1021/ es960937t. Rashidi, N.A., Yusup, S., 2016. Overview on the potential of coal-based bottom ash as low-cost adsorbents. ACS Sustain. Chem. Eng. 4 (4), 1870e1884. https://doi.org/ 10.1021/acssuschemeng.5b01437. Rayalu, S., Meshram, S.U., Hasan, M.Z., 2000. Highly crystalline faujasitic zeolites from fly ash. J. Hazard Mater. 77 (1e3), 123e131. https://doi.org/10.1016/S03043894(00)00212-0. Saceda, J.J.F., de Leon, R.L., Rintramee, K., Prayoonpokarach, S., Wittayakun, J., 2011. Properties of silica from rice husk and rice husk ash and their utilization for zeolite Y synthesis. Quim. Nova 34 (8), 1394. U1289. https://doi.org/10.1590/ S0100-40422011000800018. Shah, B., Tailor, R., Shah, A., 2011a. Sorptive sequestration of 2-chlorophenol by zeolitic materials derived from bagasse fly ash. J. Chem. Technol. Biotechnol. 86 (10), 1265e1275. https://doi.org/10.1002/jctb.2646. Shah, B., Tailor, R., Shah, a.A., 2011b. Adaptation of bagasse fly ash, a sugar industry solid waste into zeolitic material for the uptake of phenol. Environ. Prog. Sustain. Energy 30 (3), 358e367. https://doi.org/10.1002/ep.10492. Shah, B.A., Patel, H.D., Shah, A.V., 2011c. Equilibrium and kinetic studies of the adsorption of basic dye from aqueous solutions by zeolite synthesized from bagasse fly ash. Environ. Prog. Sustain. Energy 30 (4), 549e557. https://doi.org/ 10.1002/ep.10505. Shah, B.A., Shah, A.V., Mistry, C.B., Tailor, R.V., Patel, H.D., 2011d. Surface modified bagasse fly ash zeolites for removal of reactive black-5. J. Dispersion Sci. Technol. 32 (9), 1247e1255. https://doi.org/10.1080/01932691.2010.505550. Shah, B., Tailor, R., Shah, A., 2012a. Equilibrium, kinetics, and breakthrough curve of phenol sorption on zeolitic material derived from BFA. J. Dispersion Sci. Technol. 33 (1e3), 41e51. https://doi.org/10.1080/01932691.2010.530079. Shah, B., Tailor, R., Shah, A., 2012b. Zeolitic bagasse fly ash as a low-cost sorbent for the sequestration of p-nitrophenol: equilibrium, kinetics, and column studies. Environ. Sci. Pollut. Res. 19 (4), 1171e1186. https://doi.org/10.1007/s11356-0110638-6. Shah, B.A., Abebe, A.A., Shah, A.V., 2017a. Microwave-synthesized bariumimpregnated siliceous zeolitic material derived from bagasse fly ash for uptake of aniline. Arabian J. Sci. Eng. 42 (1), 139e152. https://doi.org/10.1007/ s13369-016-2083-9. Shah, B.A., Pandya, D.D., Shah, H.A., 2017b. Impounding of ortho-chlorophenol by zeolitic materials adapted from bagasse fly ash: four factor three level BoxBehnken design modelling and optimization. Arabian J. Sci. Eng. 42 (1), 241e260. https://doi.org/10.1007/s13369-016-2294-0. Singer, A., Berkgaut, V., 1995. Cation exchange properties of hydrothermally treated coal fly ash. Environ. Sci. Technol. 29 (7), 1748e1753. https://doi.org/10.1021/ es00007a009. Volli, V., Purkait, M.K., 2015. Selective preparation of zeolite X and A from fly ash and its use as catalyst for biodiesel production. J. Hazard Mater. 297, 101e111. https://doi.org/10.1016/j.jhazmat.2015.04.066. Wang, D.D., Wang, J.N., 2017. Electrospinning Polyvinyl alcohol/silica-based nanofiber as highly efficient adsorbent for simultaneous and sequential removal of Bisphenol A and Cu(II) from water. Chem. Eng. J. 314, 714e726. https://doi.org/ 10.1016/j.cej.2016.12.037.