Hydrometallurgy 99 (2009) 170–174
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Hydrometallurgy j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / h yd r o m e t
Removal of chromium(III) by cation exchange resin, Indion 790 for tannery waste treatment S.K. Sahu a,⁎, P. Meshram a, B.D. Pandey a, V. Kumar a, T.R. Mankhand b a b
Metal Extraction & Forming Division, National Metallurgical Laboratory, CSIR, Jamshedpur - 831 007, India Dept. of Metallurgical Engineering, IT, BHU, Varanasi - 221 005, India
a r t i c l e
i n f o
Article history: Received 5 May 2009 Received in revised form 6 August 2009 Accepted 6 August 2009 Available online 13 August 2009 Keywords: Chromium(III) Tannery effluent Cation exchange Indion 790 resin Sulfonated styrene-DVB resin
a b s t r a c t Extraction of chromium(III) from a model solution and from a tannery waste solution was studied by ion exchange using Indion 790 resin which is a macro-porous strongly acidic cation exchange resin of sulfonated polystyrene group. The resin was found to be selective for the sorption of chromium(III) in the pH range 0.5–3.5 from a model solution containing 500 ppm Cr(III). Beyond pH 3.5 extraction of chromium(III) drastically decreased from 92% to 76%. Sorption of chromium(III) on Indion 790 followed the Freundlich isotherm with a high Freundlich constant value (Kf = 8.57) confirming strong chemical interaction of the metal ion with the resin. Desorption of chromium(III) from the loaded resin increased with the increase in concentration of eluant (5–20% H2SO4). With 20% sulfuric acid solution 89% Cr(III) was eluted in two stages. The bench scale results were also validated in continuous mode in a fixed bed column and for the recovery of chromium(III) from a tannery solution. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Tanning is the main process that protects leather against some environmental effects such as microbial degradation, heat, sweat or moisture, etc. Tanning process using chromium compounds is one of the most common methods for processing of hides. There are more than 2500 tannery units in India with 80% of tanneries engaged in chrome tanning process (Ram et al., 1997). Tannery effluent is a major source of aquatic pollution in India with high chemical oxygen demand, biological oxygen demand and chromium content. The discharge limit of chromium is 0.2 mg/L for stream and 0.1 mg/L for irrigation water as prescribed by Central Pollution Control Board (CPCB), India. The traditional technique used for chromium control in the waste water involves chemical precipitation of chromium(III) as Cr(OH)3 and secure dumping. But, experimental evidences show that the kinetics of the transformation of chromium(III) to chromium(VI) is rapid enough in the presence of even mild oxidants (Pastore et al., 2004). Chromium(VI) is highly toxic as a potential carcinogenic agent due to its high oxidation potential and relatively small size, which enables it to penetrate through biological cell membranes. The landfills of chromium may thus be considered as a potential hazard to the environment. Adsorption (Rivera-Utrilla and Sanchez-Polo, 2003), ion exchange (Cavaco et al., 2007), solvent extraction (Lanagan and Ibana, 2003),
⁎ Corresponding author. Tel.: +91 657 2345275. E-mail address: sushanta_sk@yahoo.com (S.K. Sahu). 0304-386X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.hydromet.2009.08.002
membrane separation (Lambert et al., 2006), bioremediation (Srivastava and Thakur, 2006) etc. are the common techniques for removal and recovery of chromium from industrial waste streams. Recently, Agrawal et al. (2006) have reviewed the applicability of conventional and promising techniques for treatment of chromium containing wastes. Some studies related to recovery or recycling of chromium from spent tanning liquors have been reported (Fabiani et al., 1996; O'Dwyer and Hodnett, 1995; Pandey et al., 1996; Sreeram and Ramasami, 2003; Aravindhan et al., 2004; Guo et al., 2006; Fahim et al., 2006). Out of several options for removing chromium from wastewaters, ion exchange is considered to be quite promising. Several studies for chromium removal by strongly acidic ion exchange resins have been described in the literature (Gode and Pehlivan, 2006; Kocaoba and Akcin, 2004; Gode and Pehlivan, 2003). Both batch and continuous ion exchange process for the recovery of chromium(III) from aqueous chloride solution by using Amberlite IR-120 resin are described by Alguacil et al. (2004). Whilst Chiarizia et al. (1993) have shown the effectiveness of diphonix — a commercially available dual mechanism polyfunctional resin (Eichrome Industries Inc.) containing sulfonic and diphosphonic acid groups, for separating iron(III) and chromium(III) in highly acidic solutions. Rengaraj et al. (2003) have studied the kinetics of chromium(III) extraction from electronic process waste water using three different cation exchange chelating resins. The development of newer chelating sorbents by introducing new functionalities into the aromatic ring, for recovery of chromium from wastewater has also been attempted (Pramanik et al., 2007; Chattopadhyay et al., 1997). A resin containing organic functional group with strong metal chelate forming capabilities
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has been reported. Such chelating resins viz. Chelex-100 and Lewatit TP207 have been used to extract chromium(III) (Gode and Pehlivan, 2003). Gode and Pehlivan (2006) have also studied in detail the removal of chromium(III) from aqueous solution using Lewatit S100, a cation exchange resin having sulfonated polystyrene group. The kinetics of extraction of chromium(III) with this resin seems to be very slow (150 min), and loading capacity is also not very encouraging (20 mg/g of Lewatit S100 resin). Thus, it is desirable to look for new resins with faster kinetics and higher loading capacity. In the present work the removal of chromium(III) from aqueous solutions, particularly model waste tanning solutions using a new cationic resin (Indion 790) is investigated. Indion 790 is a macroporous strongly acidic cation exchange resin of sulfonated polystyrene group (Indion 790 Catalogue, Ion Exchange Ltd., 2002). The resin has got excellent physical, chemical and thermal stability, good ion exchange kinetics and high exchange capacity. The resin is considered suitable for application in removal of heavy metals from wastewater. Sorption equilibria for this resin at room temperature have been evaluated using Langmuir and Freundlich isotherms, and an attempt has been made to understand the kinetic behavior of the process. A preliminary test has also been carried out to understand the behavior of the resin for extraction of chromium(III) in a column.
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In order to validate the process developed with model tanning waste solution, removal of chromium(III) from actual tanning waste solution was also investigated. The tannery waste solution is a mixture of biogenic matter of hides and a large variety of organic and inorganic chemicals (Murugananthan et al., 2004; Reemtsma and Jekel, 1997). Besides a high salt content, the main inorganic contaminant of tannery waste solution is chromium (0.5–5 g/L) from chrome-tanning. The organic contaminants present in the wastewater are a complex mixture of biogenic matter of hides and large variety of organic chemicals added during the tanning process. The main organic contaminants are aliphatic sulfonates, sulfates, aromatic and aliphatic ethoxylates, sulfonated poly-phenols, acrylic acid, fatty acids, dye, proteins, soluble carbohydrates, etc. The organic load of tannery waste solution is usually characterized by its chemical oxygen demand (COD) in the range 3000–10,000 mg/L and biological oxygen demand (BOD) in the range 1000–4000 mg/L. The waste solution used in this work was obtained from Central Leather Research Institute (CLRI), Chennai, which had COD of 4400 mg/L and BOD of 2200 mg/L as given in Table 2. The sample was collected by CLRI from a plant situated in Chennai. The tanning waste solution was diluted 10 times and used for extraction of Cr(III) with Indion 790 resin in a shake flask at A/R ratio of 50. 3. Results and discussion
2. Experimental
3.1. Effect of mixing time
A synthetic stock solution containing 1000 ppm Cr(III) was prepared by dissolving 5.12 g of CrCl3·6H2O in 1000 mL distilled water. Chromium(III) solutions of desired concentrations were prepared by diluting the stock solution with distilled water. The resin Indion 790 was obtained from Ion Exchange, India. The resin is a strongly acidic cation exchanger with styrene-divinyl benzene copolymers and sulfonic acid as the functional group. The physical and chemical properties of the resin are shown in Table 1. Before experiments, about 20 g of Indion 790 resin was washed properly with 200 mL distilled water and pre-treated with 50 mL of 5% HCl for 10 min. The treated resin was again washed properly with distilled water in order to remove excess Cl− and dried at room temperature for 24 h. To study the extraction of chromium(III) by ion exchange, 50 mL of the aqueous solution was shaken with 1.0 g of dry resin in a 250 mL flask at 250 oscillations/min at room temperature. The loaded resin was filtered, washed thoroughly with distilled water and then chromium was eluted with 50 mL of 5–20% sulfuric acid solution. Chromium in solution was analyzed by Atomic Absorption Spectrometer (ECIL, India) and the material balance was checked. Sorption isotherms were determined by repeatedly loading 1 g of the resin with 500 ppm Cr(III) solution for eight times. The extraction data were fitted into the Freundlich isotherm model in order to determine the sorption performance and capacity of Indion 790. Ion exchange experiments were also carried out in a small column packed with 1.0 g (1.25 mL) of the resin with the Cr(III) solution percolated over the resin bed at a flow rate of 2 mL/min using a peristaltic pump.
3.2. Effect of pH on the extraction of chromium(III) The extraction of chromium from 500 ppm Cr(III) solutions of various pH remained almost constant (92%) within the pH range 0.5–3.5 (Fig. 2) when the resin was loaded to about 30% of its capacity. Therefore the equilibrium constant for ion exchange is large and the distribution coefficient remains sufficiently high even at low pH. A similar trend has been reported by Rengaraj et al. (2001) for extraction of Cr(III) with IRN 77. But with Lewatit S 100, Gode and Pehlivan (2006) reported that Log Kd was 0.6 at pH 1.5 rising to 1.5 at pH 3.5. However, for all these resins Cr(III) extraction decreased beyond pH 3.5. At pH 5.0 only 65% Cr(III) was extracted due to the hydrolysis Table 2 Composition of the tanning bath solution collected from CLRI, Chennai.
Table 1 Properties of Indion 790 resin. Ionic form Functional group Matrix type Resin type Particle size (mm) Moisture (%) Max. operating temp. (°C) pH range Total exchange capacity (meq/mL)
Aqueous feed solutions containing 500 and 1000 ppm Cr(III) were contacted with Indion 790 at A/R ratio of 50 and 2.74 pH for various time intervals and the results are depicted in Fig. 1. It was found that the extraction of chromium(III) increased with time and decreasing chromium concentration. About 92% Cr(III) was extracted from 500 ppm solution in 12 min, but only 78% Cr(III) was extracted from 1000 ppm solution after 16 min due to the less availability of active sites. The kinetics of adsorption of Cr(III) with Indion 790 appears to be 10 times faster as compared to other resins of similar matrix characteristics viz. IRN 77 (Rengaraj et al., 2001) and Lewatit S 100 (Gode and Pehlivan, 2006). With these resins, equilibrium times of 150 min have been reported with solutions containing 50–100 ppm Cr(III) and A/R ratios of 333 and 60, respectively.
H+ –SO− 3 Styrene-DVB Macro-porous strong acidic cation 0.3–1.2 51–55 120–150 0–14 1.9
Constituent
g/L
Cr(III) Fe(III) Al(III) COD BOD SO2− 4 NaCl pH
4.57 0.05 0.12 4.4 2.2 12.0 60 2.5
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Fig. 1. Effect of mixing time on extraction of chromium(III) with Indion 790 at different chromium(III) concentrations. (pH = 2.74, A/R = 50).
Fig. 3. Saturation loading of Indion 790 resin with 500 ppm chromium(III) solution. (pH = 2.74, t = 15 min, A/R = 50).
of Cr3+ ion forming Cr(OH)3, Cr(OH)SO4 (Stunzi and Marty, 1983; Lanagan and Ibana, 2003).
S 100 due to the higher solution concentrations used. The loading capacity of IRN 77 was 35.4 mg/g (Rengaraj et al., 2001) with an aqueous feed of 100 ppm Cr(III) and that of Lewatit S 100 was 20 mg/g (Gode and Pehlivan, 2006) with 50 ppm Cr(III) initially.
3.3. Sorption isotherm An adsorption isotherm is used to characterize the equilibria between the amount of adsorbate that accumulates on the adsorbent and the concentration of the dissolved adsorbate. In order to understand the nature of adsorption isotherm of chromium(III) on Indion 790, 1.0 g of the resin was repeatedly contacted with fresh 500 ppm Cr(III) solution. The trend of extraction of chromium(III) by the resin is shown in Fig. 3, which indicates that in eight stages 69 mg Cr(III) was transferred to the resin. The data so obtained were fitted into the Freundlich model which assumes that the uptake of metal ions occurs on a heterogeneous surface by monolayer sorption. The model is commonly described by: log q = ð1 = nÞ log Ce + log Kf
3.4. Kinetics of extraction Kinetics of sorption describes the solute uptake rate on the resin and it also governs the required residence time of sorption reaction. In order to determine the kinetics of sorption of chromium(III) onto Indion 790 resin, kinetic data were fitted into the Lagergren first order model. The first order equation (Lagergren, 1898) is generally expressed after integration as:
logðqe −qt Þ = log qe −
k1 t 2:303
ð2Þ
ð1Þ
where q = Cr(III) loaded on resin (mg/g); Ce = equilibrium concentration Cr(III); Kf = Freundlich constant. The plot of log q versus log Ce gave a straight line with a correlation coefficient (R2) of 0.989 (Fig. 4) indicating that the amount of Cr(III) adsorbed on the surface of Indion 790 depends linearly on the equilibrium concentration in solution. The Freundlich constant (Kf) was found to be 8.57 and the value of n (2.96) between 1 and 10 indicates strong chemical interaction and ion exchange between the resin and chromium(III) (McKay et al., 1982). From the adsorption model the loading capacity of Indion 790 for Cr(III) was determined to be 86.9 mg/g resin which was higher than that of other resins of similar characteristics viz. IRN 77 and Lewatit
where qe and qt are adsorption capacity of Indion 790 at equilibrium and time t k1 is the first order rate constant (min− 1). Fig. 5 indicates the plot of log (qe −qt) against contact time for two concentrations of chromium(III) solution. From the slopes and intercept, values k1 were determined to be 0.281 min− 1 for 500 ppm Cr(III) and 0.071 min− 1 for 1000 ppm Cr(III) with correlation coefficients (R2) around 0.96–0.98. Various mechanisms in ion exchange phenomena are reported to control the kinetics. The major rate limiting steps are: 1) mass transfer of solute from solution to the boundary film; 2) mass transfer of metal ions from boundary film to surface; 3) sorption and ion exchange of ions onto sites; 4) internal diffusion of solute. The first and second steps depend on the mixing and homogeneity of the solution and the
Fig. 2. Effect of pH on extraction of chromium(III) with Indion 790. (A/R = 50, t = 15 min).
Fig. 4. Freundlich isotherm for sorption of chromium(III) with Indion 790.
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Fig. 5. First order kinetics for ion exchange of chromium(III) with Indion 790.
third step is fast so internal particle diffusion of chromium(III) limits the process as the surface sites become occupied. 3.5. Desorption study Elution of chromium(III) from loaded resin was studied using various concentrations (5–20% w/v) of sulfuric acid solutions as eluant (Fig. 6). Desorption of chromium(III) increased with increasing sulfuric acid concentration. With 20% sulfuric acid solution 89% Cr(III) was eluted in two stages, whereas in the third stage no chromium was eluted. This may be due to formation of Cr(OH)SO4 species (Rengaraj et al., 2001), which is difficult to elute under normal condition. 3.6. Extraction of chromium(III) in column In order to validate the shake flask results on continuous mode a 500 ppm Cr(III) solution at pH 2.74 was passed through a small column bed containing 1.0 g (1.25 mL) Indion 790 at a flow rate maintained at 2.0 mL min− 1. The plot of chromium(III) concentration in the raffinate versus bed volume (Fig. 7) shows a breakthrough of Cr (III) after 40 bed volumes and saturation of the resin after about 160 bed volumes or the passage of about 200 mL of solution at room temperature. A saturation loading of 65 mg Cr(III)/g resin was obtained which is only slightly lower than the maximum loading determined above from the isotherm. Larger scale column tests are required with slower flow rates to properly achieve equilibrium raffinate concentrations and assess breakthrough points and maximum loadings. After washing the loaded resin with distilled water, chromium(III) was eluted with 20% (w/v) H2SO4 at a flow rate of 2.0 mL/min which removed a maximum of 79% Cr(III) after the passage of 200 mL eluant.
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Fig. 7. Extraction of chromium(III) with Indion 790 resin in column. (Resin = 1.0 g, [Cr(III)] = 500 ppm, pH = 2.74, flow rate 2.0 mL/min).
The elution may be further improved by desorption of the metal immediately and by slower flow rates. 3.7. Recovery of chromium(III) from waste tannery solution In order to examine the industrial application of the process developed with Indion 790, the recovery of chromium(III) from actual tannery waste solution was also studied. The solution containing 4.58 g/L chromium(III) and trace quantity of iron and aluminium was obtained from Central Leather Research Institute (CLRI), Chennai as mentioned earlier. As before, the solution was diluted to 458 ppm Cr (III) and was contacted with Indion 790 in a shake flask at equilibrium pH 2.74 and A/R ratio of 50. The results indicate that 95% Cr(III) was extracted in three stages without detectable extraction of Fe(II) and Al (III). From the loaded resin 93% Cr(III) was eluted with 20% H2SO4 in single stage. To achieve the discharge level as prescribed by CPCB (India), the A/R ratios must be decreased to produce the raffinate with acceptable chromium level and further long term tests must be carried out with columns of resins to determine the equilibrium chromium levels in the eluant before breakthrough occurs, and whether the organics in the tannery waste poison the resin over time. 4. Conclusions Extraction of chromium(III) from model solutions by the strong acid cation exchange resin Indion 790 may be applied to tannery waste. The resin extracted up to 92% Cr in 15 min from a 500 ppm Cr (III) solution at pH 2.7, but less at higher concentrations. In the pH range 0.5–3.5, Cr(III) extraction was almost constant with 3 times excess resin, but beyond pH 3.5 extraction decreased due to hydrolysis of Cr3+. Sorption of chromium(III) on Indion 790 followed the Freundlich isotherm and a high value of Kf confirmed strong chemical interaction/ion exchange of the metal ion with the resin. Extraction of chromium(III) with Indion 790 followed first order kinetics. The maximum loading capacity was found to be 86.9 mg/g of resin in 500 ppm Cr(III), which was higher compared to other resins reported in the literature using more dilute solutions. Desorption of 89% Cr(III) from the loaded resin was achieved in two stages with 20% H2SO4 eluant. Extraction of 96% Cr(III) from a diluted waste solution from a tannery containing 458 ppm Cr(III) was also carried out in three stages and 93% Cr(III) was eluted with 20% H2SO4 solution in single stage. Acknowledgements
Fig. 6. Elution study for chromium(III) from loaded Indion 790 resin. A/R = 50.
Authors are thankful to Prof. S. P. Mehrotra, Director, National Metallurgical Laboratory, Jamshedpur for giving permission to publish the paper. Thanks are also due to Dr. B. U. Nair, CLRI, Chennai for
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providing the solution from tannery. The financial support received from Planning Commission, Govt. of India, through Council of Scientific & Industrial Research (CSIR) New Delhi under 10th five year plan is gratefully acknowledged. References Agrawal, A., Kumar, V., Pandey, B.D., 2006. Remediation options for the treatment of electroplating and leather tanning effluent containing chromium—a review. Miner. Process. Extractive Metall. Rev. 27, 99–130. Alguacil, F.J., Alonso, M., Lozano, L.J., 2004. Chromium(III) recovery from waste acid solution by ion exchange processing using Amberlite-IR 120 resin: batch and continuous ion exchange modeling. Chemosphere 57, 789–793. Aravindhan, R., Madhan, B., Rao, J.R., Nair, B.U., Ramasami, T., 2004. Bioaccumulation of chromium from tannery wastewater: an approach for chrome recovery and reuse. Environ. Sci. Technol. 38, 300–306. Cavaco, S.A., Fernandes, S., Quina, M.M., Ferreira, L.M., 2007. Removal of chromium from electroplating industry effluents by ion exchange resins. J. Hazard. Mater. 144, 634–638. Chattopadhyay, P., Sinha, C., Pal, D.K., 1997. Preparation and properties of a new chelating resin containing imadazolyl azo groups. Fresen. J. Anal. Chem. 357, 368–372. Chiarizia, R., Horwitz, E.P., Gatrone, R.C., Alexandratos, S.D., Trochimczuk, A.Q., Crick, D.W., 1993. Uptake of metal ions by a new chelating ion exchange resin, part 2: acid dependencies of transition and post transition metal ions. Solvent Extr. Ion Exch. 11, 967–985. Fabiani, C., Ruscio, F., Spadoni, M., Pizzichini, M., 1996. Chromium(III) slats recovery process from tannery wastewaters. Desalination 108, 183–191. Fahim, N.F., Barsoum, B.N., Eid, A.E., Khalil, M.S., 2006. Removal of chromium(III) from tannery wastewater using activated carbon from sugar industrial waste. J. Hazard. Mater. 136, 303–309. Gode, F., Pehlivan, E., 2003. A comparative study of two chelating ion-exchange resins for the removal of chromium (III) from aqueous solution. J. Hazard. Mater. 100, 231–243. Gode, F., Pehlivan, E., 2006. Removal of chromium (III) from aqueous solutions using Lewatit S 100: the effect of pH, time, metal concentration and temperature. J. Hazard. Mater. 136, 330–337. Guo, Zhen-Ren, Zhang, Guangming, Fang, Jiande, Dou, Xiudong, 2006. Enhanced chromium recovery from tanning wastewater. J. Clean. Prod. 14, 75–79. Indion 790 Catalogue, Ion Exchange Ltd., 2002.
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