Reduction of Cr(VI) by palladized biomass of Desulfovibrio vulgaris NCIMB 8303

Palladized biomass of Desulfovibrio vulgaris (Bio‐Pd(0)) reduced Cr(VI) to Cr(III) at an initial rate four‐fold higher than chemically‐prepared Pd(0) metal. Optimal Cr(VI) reduction by suspended Bio‐Pd(0) occurred at pH 3, whereas pH did not affect the rate of Cr(VI) reduction by Bio‐Pd(0) immobilized in agar beads. The rate of Cr(VI) reduction was concentration‐dependent below 300 µmol dm^?3, and application of enzyme kinetics, considering Bio‐Pd(0) as an ‘artificial enzyme’, gave an apparent K_m (K_mapp) of approx. 650 µmol dm^?3 and V_max of 1667 nmol h^?1 mg Pd(0) for suspended Bio‐Pd(0). The potential of Bio‐Pd(0) as a method for the treatment of Cr(VI)‐wastes is discussed. Copyright © 2005 Society of Chemical Industry     

Cr(VI) reduction by bio and bioinorganic catalysis via use of bio‐H2: a sustainable approach for remediation of wastes

Use of biologically‐produced hydrogen (bio‐H₂) as an electron donor for Cr(VI) reduction by native and palladized cells of Desulfovibrio vulgaris NCIMB 8303 was demonstrated. The bio‐H₂ was produced fermentatively by Escherichia coli HD701 (a strain upregulated with respect to formate hydrogenlyase expression) using glucose solution or two industrial confectionery wastes as fermentable substrates. Maximum Cr(VI) reduction occurred at the expense of bio‐H₂ using palladized biomass (bio‐Pd(0)), with negligible residual Cr(VI) remaining from a 0.5 mmol dm^?3 solution after 2.5 h. Use of bio‐H₂ as the electron donor for Cr(VI) reduction by agar‐immobilized bio‐Pd(0) in a continuous‐flow system gave 90% reduction efficiency at a flow residence time of 0.7 h, which was maintained for the duration of bio‐H₂ evolution by E. coli HD701. This study shows the potential to remediate toxic metal waste at the expense of food processing waste, as a sustainable alternative to landfilling. Copyright © 2007 Society of Chemical Industry     

Biological Removal of Aqueous Hexavalent Chromium

The conventional chemical reduction of Cr(VI) to Cr(III) and subsequent Cr(OH)₃ precipitation are expensive due to the use of large amounts of chemicals and the generation of chemical sludges. An attempt was carried out for microbial Cr(VI) removal in an anaerobic chemostat fed with an acetate-containing synthetic medium. With 26 mg Cr(VI) dm⁻³ in the influent, almost complete removal of Cr(VI) was achieved at dilution rates of 0·15 and 0·32 day⁻¹ at 20°C and at 35°C, respectively. The optimum Cr(VI) mass loading and the specific Cr(VI) applied rates were found to be 5 mg Cr(VI) dm⁻³ day⁻¹ and 0·02 mg Cr(VI) mg⁻¹ VSS day⁻¹, respectively. Either the influent Cr(VI) concentration or the dilution rate could be adjusted to maintain an efficient removal of Cr(VI) in a continuous operation. Since the Cr(VI)-reducing activity is associated with the biomass concentration in the system, recycling the effluent solids is essential for practical application. In a batch reactor with the biomass collected from the chemostat, NaAc degradation appeared to be proportional to Cr(VI) reduction with the ratio of 9 mg C mg⁻¹ Cr(VI) at 35°C. As reactions proceeded, the oxidation–reduction potential correspondingly decreased and both pH and alkalinity increased. © 1997 SCI.     

Dynamical modeling of the electrochemical process to remove Cr (VI) from wastewaters in a tubular reactor

This work is aimed at obtaining and calibrating a dynamical model of the electrochemical reduction of Cr(VI) in a tubular continuous reactor with a spiral wire shaped anode at different conditions of pH (1.0 to 2.0) and residence times. An industrial wastewater sampled from a Mexican electroplating industry with about 1000 mg dm^?3 of Cr(VI) was used for the experiments. It was found that pH exerts a strong influence on the performance of electrochemical reduction of Cr(VI). Thus at a wastewater influent pH = 1.0 and a residence time in the reactor of 38.5 min it is possible to reduce the Cr(VI) concentration from 1000 to 0.37 mg dm^?3. However at an influent pH higher than 1.5, an effluent Cr(VI) concentration lower than 0.5 mg dm^?3 cannot be obtained. A more complete dynamic model was applied incorporating pH and the dispersion effects that affect the electrochemical Cr(VI) removal. The model, which adequately describes the performance of the electrochemical process, can be used to optimize the performance of this kind of reactor with more reliability. Copyright © 2007 Society of Chemical Industry     

Modelling of Cr(VI) removal from polluted groundwaters by ion exchange

This work reports the viability and modelling of the removal of Cr(VI) from polluted groundwaters by means of ion exchange using the resin Lewatit MP‐64. Feed groundwaters that contained Cr(VI) at an average concentration of 2431 mg dm^?3 and 1187 mg dm^?3 of chloride and 1735 mg dm^?3 of sulfate as main anions were acidified to a pH of 2.0 prior to the removal process. Dynamic experiments were carried out in a fixed bed column with feed waters at flow rates in the range of 2.78 × 10^?7 m³ s^?1 to 5.55 × 10^?7 m³ s^?1. Regeneration was achieved with NaOH (2 mol dm^?3). From the experimental results, the equilibrium of the ion exchange reaction was successfully modelled, obtaining an equilibrium constant (K′_AB) = 44.90. Finally, a mass balance that included mass transfer resistances in the liquid and solid phases was developed and from the comparison between simulated and experimental data the value of the effective intraparticle diffusivity (D_s) was determined as 1.43 × 10^?12 m² s^?1. Copyright © 2004 Society of Chemical Industry     

Effect of pre‐treatments on the biosorption of Chromium (VI) ions by the dead biomass of Rhizopus arrhizus

BACKGROUND: This work fulfils the need to develop an eco‐friendly biosorbent, elucidating the mechanism of biosorption. Removal of Cr(VI) by Rhizopus arrhizus was investigated in batch mode. Enhancement in the performance of the biosorbent was attempted by pre‐treating the biomass with inorganic and organic acids, chelating agent, cross‐linker and an organic solvent followed by autoclaving. The surface characterization of the biomass was carried out by potentiometric titration, surface area analysis, infrared spectroscopy, chemical modification of the biomass and scanning electron microscopy. RESULTS: All the physico‐chemical treatments of the biosorbent improved Cr(VI) uptake compared with the native biomass (21.72 mg g^?1). The highest biosorption capacity (31.52 mg g^?1) was achieved after pre‐treating the biomass with 0.5 mol L^?1 HNO₃ followed by autoclaving. Surface characterization of the biomass using pH_zpc, potentiometry and Fourier transform infrared (FTIR) analysis revealed the role of amino and carboxyl groups in Cr(VI) removal by electrostatic attraction. Chemical modification of amino and carboxyl groups significantly decreased Cr(VI) uptake capacity confirming their role in biosorption. SEM analysis showed adsorption of Cr(VI) on the biosorbent surface. CONCLUSION: Rhizopus arrhizus biomass proved to be an effective and low cost alternative biosorbent for removal of Cr(VI) from aqueous solutions. Copyright © 2011 Society of Chemical Industry     

Characteristics of gold biosorption from cyanide solution

Gold adsorption from cyanide solution by bacterial (Bacillus subtilis), fungal (Penicillium chrysogenum) and seaweed (Sargassum fluitans) biomass was examined. At pH 2.0, these biomass types were capable of sequestering up to 8.0 µmol g⁻¹, 7.2 µmol g⁻¹ and 3.2 µmol g⁻¹, respectively. An adverse effect of increasing solution ionic strength (NaNO₃) on gold biosorption was observed. Gold‐loaded biomass could be eluted with 0.1 mol dm⁻³ NaOH with efficiencies higher than 90% at pH 5.0 at the Solid‐to‐Liquid ratio, S/L, = 4 (g dm⁻³). Cyanide mass balances for the adsorption, desorption as well as for the AVR process indicated the stability of the gold‐cyanide which did not dissociate either upon acidification or upon binding by biomass functional groups. Gold biosorption mainly involved anionic AuCN₂⁻ species bound by ionizable biomass functional groups carrying a positive charge when protonated. FTIR analyses indicated that the main biomass functional groups involved in gold biosorption are most probably nitrogen‐containing weak base groups. The present results confirmed that waste microbial biomaterials have some potential for removing and concentrating gold from solutions where it occurs as a gold‐cyanide complex. © 1999 Society of Chemical Industry     

Reduction of hexavalent chromium by Bacillus sp. isolated from chromite mine soils and characterization of reduced product

BACKGROUND: The reduction of highly mobile and toxic hexavalent chromium by bacterial strains is considered to be a viable alternative to reduce Cr(VI) contamination, in soils and water bodies, emanating from the overburden dumps of chromite ores and mine drainage. The present study reports the isolation of Cr(VI) resistant bacterial strains from an Indian chromite mine soil and their potential use in reduction of hexavalent chromium. RESULTS: Among the isolates, a bacterial strain (CSB‐4) was identified as Bacillus sp. based on standard biochemical tests and partial 16SrRNA gene sequencing, which was tolerant to as high as 2000 mg L^?1 Cr(VI) concentration. The strain was capable of reducing Cr(VI) to Cr(III) in different growth media. Under the optimized conditions pH ～7.0, 100 mg L^?1 Cr(VI), 35 °C temperature and stirring speed 100 rpm, CSB‐4 reduced more than 90% of Cr(VI) in 144 h. The time course reduction data fitted well an exponential rate equation yielding rate constants in the range 3.22 × 10^?2 to 6.5 × 10^?3 h^?1 for Cr(VI) concentration of 10–500 mg L^?1. The activation energy derived from temperature dependence rate constants between 25 and 35 °C was found to be 99 kJ mol^?1. The characterization of reduced product associated with bacterial cells by SEM‐EDS, FT‐IR and XRD was also reported. CONCLUSION: Reasonably high tolerance and reduction ability of indigenous Bacillus sp. (CSB‐4) for Cr(VI) under a wide range of experimental conditions show promise for its possible use in reclamation of chromite ore mine areas including soils and water bodies. Copyright © 2010 Society of Chemical Industry     

Electroreduction of hexavalent chromium by polyaniline

BACKGROUND: A plate‐gap model interpretation of enzymatic reaction kinetics and rotating disc voltammetry were applied for evaluation of the nature of the reaction of the electroreduction of Cr(VI) (as dichromate ions) on a polyaniline (PANI)‐modified glassy carbon (GC) electrode. RESULTS: The kinetic parameters (the maximal current (V_max) and Michaelis constant (K_M)) for electroreduction of Cr(VI) on the PANI‐modified GC electrode were determined as V_max = 0.34 × 10^?7 mol cm^?3 s^?1 and K_M = 0.47 × 10^?6 mol cm^?3. The reduction of dichromate is intensified by PANI film growth. CONCLUSION: To characterise the electroreduction of Cr(VI) on a PANI‐modified GC electrode, the kinetic parameters of the reaction were determined using a plate–gap model interpretation of enzymatic reaction kinetics and rotating disc voltammetry. The catalytic nature of Cr(VI) electroreduction on the PANI‐modified electrode has been shown. Copyright © 2009 Society of Chemical Industry     

Effect of an electric field on the transport of Th(IV) in the presence of Eu(III) and U(VI) through supported liquid membrane containing di‐2‐ethylhexylphosphoric acid

This paper investigates the transport of Th(IV) ions in nitric acid media through a supported liquid membrane (SLM) impregnated with di‐2‐ethylhexylphosphoric acid (HDEHP) in kerosene using an electric field. The transport was carried out in a three compartment cell fitted with microporous cellulose nitrate (SLM) and cation exchange membrane (Nafion). The effect of different parameters including nitric acid concentration in the feed solution, HDEHP concentration in the membrane, and HCl concentration were studied. The optimal conditions for Th(IV) transport were 0.1 mol dm^?3 HDEHP, 10^?3 mol dm^?3 HNO₃ in the feed solution, 1 mol dm^?3 HCl in compartment 2 and 1 mol dm^?3 HCl in compartment 3 at 25 °C. Under the optimal conditions of Th(IV) transport the recovery factor after 90 min was 0.25 without applying an electrostatic field, compared with 0.9 when the electric field was applied. The effect of electric current on the flux of Th(IV) through the membrane was also studied. The flux increased as the current density increased from 10 to 30 mA cm^?2 to reach a maximum value at 30 mA cm^?2 (8 × 10^?9 g eq cm^?2 s^?1). The transport percentages of 0.3 g dm^?3 Th(IV) in the presence of 0.1 g dm^?3 Eu(III) and 1 g dm^?3 U(VI) were 66, 84 and 15%, respectively. The determined selectivities of U(VI)–Th(IV) and Th(IV)–Eu(III) were 0.12 and 0.3, respectively, after 90 min. Therefore, the order of selectivity of this system is Eu(III) > Th(IV) > U(VI). © 2001 Society of Chemical Industry     

Studies on the removal of Cr(VI) from waste-water by feldspar

The efficacy of feldspar in the removal of Cr(VI) from representative waste-water from a plating industry has been investigated in a completely mixed batch reactor at different concentrations, rate of agitation and particle size. The data obey the Langmuir isotherm for the present system and the process of uptake follows first-order kinetics. The maximum removal (91%) was observed at 40°C and pH 2.5 with initial concentration of 19.23 μmol dm^?3 Cr(VI) and 40 g dm^?3 feldspar. The process involves both film and pore diffusion to different extents. Column studies have also been carried out using a certain concentration of waste-water. More than 92% recovery has been achieved and the column can be used for 10 cycles before regeneration. The present technique seems to be quite attractive.     

Removal of chromium (VI) from aqueous solutions using poly(4‐vinyl pyridine) beads

Sorption of hexavalent chromium ions from aqueous solution by poly 4‐vinyl pyridine [Poly(4‐VP)] was studied. The batch method was applied for adsorption processes. The effects of initial ion concentration, time, pH and temperature on adsorption were investigated. A treatment time of 60 min was found to be sufficient to reach equilibrium. pH 3.0 was found as the optimum pH value for the process. The maximum adsorption performance was achieved at 86.7 mg g^?1 using 500 mg L^?1 Cr (VI) solutions. The process of adsorption of Cr (VI) was explained by Langmuir isotherm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2865–2870, 2006     

Modeling an electrochemical process to remove Cr(VI) from rinse‐water in a stirred reactor

Experimental studies were developed in a batch reactor (16 dm³), to obtain the kinetic model of Cr(VI) removal by means of an electrochemical process. An overall kinetic model was obtained and experimentally validated in a continuous stirred electrochemical reactor (16 dm³) with synthetic and industrial wastewater. To develop the mathematical model of the continuous reactor in relation to the Cr(VI) and Fe(II) concentration in the solution, a classical mass balance procedure was performed. The Cr(VI) concentration in the electrochemically‐treated waters was less than 0.5 mg dm^?3. In the electrochemical process the Cr(VI) reduction is caused by the Fe(II) released from the anode due to the electric current applied, by the Fe(II) released for the dissolution (corrosion) of the electrodes due to the acidic media, and by reduction at the cathode. During the process, reduction from Fe(III) to Fe(II) occurs. All of these different reactions cause a diminution in the quantity of sludge generated. Finally, it was found that due to the slow rate of reduction of Cr(VI) during the first part of the process it is necessary to develop a method of control to apply the process in a continuous industrial system. © 2003 Society of Chemical Industry     

Effect of pH on microbial hydrogen fermentation

The influence of initial pH of the culture medium on hydrogen production was studied using sucrose solution and a mixed microbial flora from a soybean‐meal silo. Hydrogen production was not observed at pH values of 3.0, 11.0 and 12.0 but low production was observed at pH values 5.0 and 5.5. The pH of the experimental mixture decreased rapidly and produced hydrogen gas within 30 h. Methane was not detected at initial pH values between 6.0 and 10.0. The sucrose degradation efficiency increased as the initial pH value increased from 3.0 to 9.0. The maximum sucrose degradation efficiency of 95% was observed at pH 9.0. The maximum specific production yields of hydrogen, VFAs and alcohols were 126.9 cm³ g^?1 sucrose (pH of 9.0), 0.7 gCOD g^?1 sucrose (pH of 8.0) and 128.7 mgCOD g^?1 sucrose (pH of 9.0), respectively. The relationship between the hydrogen ion concentration and the specific hydrogen production rate has been mathematically described. The best kinetic parameters on the specific hydrogen production rate were K_OH = 1.0 × 10^?7 mol dm^?3 and K_H = 1.1 × 10^?4 mol dm^?3 (r² = 0.86). The maximum specific hydrogen production rate was 37.0 cm³ g^?1 VSS h^?1. © 2002 Society of Chemical Industry     

Use of Desulfovibrio and Escherichia coli Pd‐nanocatalysts in reduction of Cr(VI) and hydrogenolytic dehalogenation of polychlorinated biphenyls and used transformer oil

BACKGROUND: Desulfovibrio spp. biofabricate metallic nanoparticles (e.g. ‘Bio‐Pd’) which catalyse the reduction of Cr(VI) to Cr(III) and dehalogenate polychlorinated biphenyls (PCBs). Desulfovibrio spp. are anaerobic and produce H₂S, a potent catalyst poison, whereas Escherichia coli can be pre‐grown aerobically to high density, has well defined molecular tools, and also makes catalytically‐active ‘Bio‐Pd’. The first aim was to compare ‘Bio‐Pd’ catalysts made by Desulfovibrio spp. and E. coli using suspended and immobilized catalysts. The second aim was to evaluate the potential for Bio‐Pd‐mediated dehalogenation of PCBs in used transformer oils, which preclude recovery and re‐use. RESULTS: Catalysis via Bio‐Pd_{D.desulfuricans} and Bio‐Pd_E.coli was compared at a mass loading of Pd:biomass of 1:3 via reduction of Cr(VI) in aqueous solution (immobilized catalyst) and hydrogenolytic release of Cl^? from PCBs and used transformer oil (catalyst suspensions). In both cases Bio‐Pd_{D.desulfuricans} outperformed Bio‐Pd_E.coli by ～3.5‐fold, attributable to a ～3.5‐fold difference in their Pd‐nanoparticle surface areas determined by magnetic measurements (Bio‐Pd_{D.desulfuricans}) and by chemisorption analysis (Bio‐Pd_E.coli). Small Pd particles were confirmed on D. desulfuricans and fewer, larger ones on E. coli via electron microscopy. Bio‐Pd_{D.desulfuricans}‐mediated chloride release from used transformer oil (5.6 ± 0.8 µg mL^?1) was comparable with that observed using several PCB reference materials. CONCLUSIONS: At a loading of 1:3 Pd:biomass Bio‐Pd_{D.desulfuricans} is 3.5‐fold more active than Bio‐Pd_E.coli, attributable to the relative catalyst surface areas reflected in the smaller nanoparticle sizes of the former. This study also shows the potential of Bio‐Pd_{D.desulfuricans} to remediate used transformer oil. Copyright © 2012 Society of Chemical Industry     

Simultaneous phenol removal and biological reduction of hexavalent chromium in a packed‐bed reactor

BACKGROUND: Phenol and hexavalent chromium are considered industrial pollutants that pose severe threats to human health and the environment. The two pollutants can be found together in aquatic environments originating from mixed discharges of many industrial processes, or from a single industry discharge. The main objective of this work was to study the feasibility of using phenol as an electron donor for Cr(VI) reduction, thus achieving the simultaneous biological removal/reduction of the two pollutants in a packed‐bed reactor. RESULTS: A pilot‐scale packed‐bed reactor was used to estimate phenol removal with simultaneous Cr(VI) reduction through biological mechanisms, using a new mixed bacterial culture originated from Cr(VI)‐reducing and phenol‐degrading bacteria, operated in draw–fill mode with recirculation. Experiments were performed for feed Cr(VI) concentration of about 5.5 mg L^?1, while phenol concentration ranged from 350 to 1500 mg L^?1. The maximum reduction/removal rates achieved were 0.062 g Cr(VI) L^?1 d^?1 and 3.574 g phenol L^?1 d^?1, for a phenol concentration of 500 mg L^?1. CONCLUSION: Phenol removal with simultaneous biological Cr(VI) reduction is feasible in a packed‐bed attached growth bioreactor. Phenol was found to inhibit Cr(VI) reduction, while phenol removal was rather unaffected by Cr(VI) concentration increase. However, the recorded removal rates of phenol and Cr(VI) were found to be much lower than those obtained from previous research, where the two pollutants were examined separately. Copyright © 2008 Society of Chemical Industry     

Anaerobic biodegradation of phenol in sulfide‐rich media

In the refinery industry, the washing processes of middle‐distillates using caustic solutions generate phenol‐ and sulfide‐containing waste streams. The spent caustic liquors generated contain phenols at concentrations higher than 60 g dm^?3(638.3 mmol dm^?3). For sulfur compounds, the average sulfide concentration was 48 g dm^?3(1500 mmol dm^?3) in these streams. The goal of this study was to evaluate the specific impact of phenol and sulfide concentrations towards the phenol‐biodegradation activity of a phenol‐acclimated anaerobic granular sludge. An inhibition model was used to calculate the phenol and sulfide inhibitory concentrations that completely stopped the phenol‐biodegradation activity (IC100). A maximum phenol‐biodegradation activity of 83 µmol g^?1 VSS h^?1 was assessed and the IC100 values were 21.8 mmol dm^?3 and 13.4 mmol dm^?3 for phenol and sulfide respectively. The limitation of the phenol biodegradation flow by phenol inhibition seemed to be related to the more important sensitivity of phenol‐degrading bacteria. The up‐flow anaerobic sludge bed reactor operating in a non‐phenol‐dependent inhibition condition did not present any sensitivity to sulfide concentrations below 9.6 mmol dm^?3. At this residual concentration, the pH and bisulfide ions' concentration might be responsible for the general collapsing of the reactor activity. Copyright © 2004 Society of Chemical Industry     

Adsorptive removal of hexavalent chromium using sawdust: Enhancement of biosorption and bioreduction

Simultaneous biosorption and bioreduction experienced by Cr(VI) species were initially validated by mixing 500 µM of Cr(VI) with 0.20 g of sawdust biosorbent. Accordingly, a complete disappearance of Cr(VI) species with emergence of 25% of Cr(III) ions was recorded; evidencing that both processes transpired simultaneously. An increase in the initial Cr(VI) concentration to 1500 µM could further induce more reduced Cr(VI) concentration. The enhancement of Cr(VI) biosorption and bioreduction was found to occur upon increasing the sawdust dosage to 4 g L^?1 and decreasing the solution pH to 2. However, the presence of a Zn(II) co-pollutant at 2500 µM had deteriorated the removal of Cr(VI) species.     

Bioaccumulation of palladium by Desulfovibrio desulfuricans

Palladium uptake by resting cell suspensions of Desulfovibrio desulfuricans NCIMB 8307 was studied without or with electron donor (formate), which gave metal uptake attributable to biosorption of Pd(II) and bioreduction of Pd(II) to Pd(0), respectively. The maximum biosorption capacity of palladium (at pH 2) was up to 196 mg Pd g^?1 dry cells (1.85 mmol g^?1; approx 20% of the dry weight). Biosorption was to 85% of the maximum in less than 10 min and the biomass was saturated within 30 min. Biosorption of Pd(II) was greater from the chloro‐ than the ammine complex and was inhibited in the presence of excess chloride ion. Bioreductive accumulation of Pd(II) from Pd(NH₃)₄²⁺ was achieved in the presence of electron donor (formate) but was also inhibited by excess Cl^?. Up to 100% of Pd(II) reduction to Pd(0) was achieved within 5 min anaerobically at pH 7 and 30 min at pH 3. Pd(0) was localized on the biomass surface using electron microscopy and was characterized using energy dispersive X‐ray microanalysis (EDAX) and X‐ray diffraction analysis (XRD). Biosorption was Pd‐specific with respect to Pt and Rh using test solutions and acid (aqua regia) leachates from spent automotive catalysts. The total Pd removed from the latter was only 15%, attributable to the inhibitory effect of residual chloride ion from the acidic extractant. Pd biorecovery is limited by the need for an improved extraction technology to minimize the formation of PdCl₄^2? in solution rather than by constraints of the Pd‐accumulating biomass. © 2002 Society of Chemical Industry     

Removal of trivalent chromium(III) from solution by biosorption in cork powder

The removal of trivalent chromium from solutions using biosorption in cork powder is described. The adsorption isotherm was determined, along with the effect of different variables, such as biomass particle size, solid–liquid ratio, reaction time, metal concentration and pH, on the efficiency of chromium removal. It was concluded that the adsorption is slow and favoured by an increase in pH. Therefore, using a solid–liquid ratio of 4 g dm^?3 it is possible to reduce the chromium concentration in the solution from 10 mg dm^?3 to less than 1.5 mg dm^?3 in 2 h at 22 °C. The kinetic studies verified that the sorption of chromium by cork was described by a second‐order model. The elution results showed that 50% of the chromium bound to the cork was eluted using 0.5 mol dm^?3 H₂SO₄ and that cork maintains its binding capacity over four cycles of biosorption/elution. © 2002 Society of Chemical Industry