Recovery Of Hexavalent Chromium Research Articles

A comparative study on the removal and recovery of hexavalent chromium from tannery wastewater using an isolated strain Aspergillus proliferans LA and a known strain Aspergillus terreus

Isolation of a potent microorganism from the soil near tanneries and a comparative analysis of the removal and recovery of different concentrations of hexavalent chromium using known strain Aspergillus terreus and isolated strain Aspergillis proliferansLA are done. The isolated fungal species from the chromium contaminated soil sites located in the industrial area of Kanpur, U.P. were tested for its potential for the removal of hexavalent chromium from wastewater streams. The experiments were conducted comparing the biosorption efficiency of the isolated species Aspergillus proliferansLA and Aspergillus terreus by varying the initial Cr (VI) concentration and media constituents. The highest removal efficiency of 99.19% was shown by the isolated species Aspergillus proliferansLA for an initial Cr (VI) concentration of 10ppm followed by increasing the concentration to 50ppm whereas Aspergillus terreus showed 78.43% removal of hexavalent chromium. This was then followed by desorption using 0.8M NaOH and 75.12% hexavalent chromium was desorbed from the cells. The isolated strain Aspergillus proliferansLA was seen to show better removal and recovery results than the known strain Aspergillus terreus.

Facile fabrication of a phosphonium-based ionic liquid impregnated chitosan adsorbent for the recovery of hexavalent chromium.

Chitosan adsorbents impregnated with a phosphonium-based ionic liquid (Chi_IL), trioctyldodecyl phosphonium chloride, were prepared for the adsorption of hexavalent chromium and compared to the performance of native chitosan. The physical and chemical properties of the adsorbents were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Effects of various parameters, such as pH, adsorbent dosage, contact time, temperature, and multi-component systems, were systematically examined. Chi_IL showed a high adsorption capacity (282.6 mg g−1) compared to native chitosan (238.1 mg g−1). The adsorption kinetics of the metals followed a pseudo-second-order kinetic model, and the experimental data were a good fit for the Freundlich isotherm model. Following the isotherm and activation energy parameter, adsorption of Cr(vi) onto Chi_IL follows a chemisorption process, possibly through an anionic exchange with the anion of the IL. The thermodynamic parameters suggested that the adsorption of Cr(vi) is a spontaneous and exothermic reaction. In the column adsorption, Chi_IL exhibited a longer column exhaustion time than that of native chitosan owing to the enhanced adsorption capacity caused by the introduction of IL. Moreover, the column with the parameters of 6 cm bed depth, 5 mL min−1 flow rate, and 50 mg L−1 was able to achieve the best performance in Cr(vi) adsorption.

Enhanced recovery of hexavalent chromium by remodeling extracellular polymeric substances through engineering Agrobacterium tumefaciens F2

Commonly used modification of materials added the operational complexity and was unsustainable for enhanced chromium recovery. Bioengineering was applied for enhancing Cr(VI) recovery in a facile and green manner. The engineered strain F2-exoY-O produced a significantly higher level of EPSs (1219 mg/L) containing more polysaccharide (59.1%) than that (44.3% polysaccharide in 686 mg/L EPSs) by wild strain F2. The proportion of glucose and galactose increased in polysaccharide in EPSs produced by F2-exoY-O. Control EPSs (411.6 mg/L) produced by wild strain F2 showed 70.5% Cr(VI) recovery at pH 3.0, by contrast, EPSs produced by engineered strain F2-exoY-O reached 88.5% at the same conditions. A minor Cr(III) existed in the aqueous solution after chromium recovery by EPS, accompanied by the increased solution pH. X-ray photoelectron spectroscopy showed that Cr(VI) was the main form on EPS with a minor Cr(III). Fourier transform infrared spectra suggested that polysaccharides (i.e. mainly hemiacetal groups) in EPSs were major participants in Cr(VI) recovery. Chelation between functional groups on EPS and Cr(VI) was the main recovery mechanism, along with a minor reduction of Cr(VI) into Cr(III) on EPSs. The enhanced recovery performance was attributed to the increased polysaccharide in EPSs produced by engineered strain F2-exoY-O. Cr(VI) recovery was enhanced by bioengineering method, providing a facile, effective and sustainable way for the preservation of chromium resource.

Carbon microfibers with tailored surface functionalities supporting iron/nickel bisalloy for highly efficient hexavalent chromium recovery

Carbon microfibers with a tailored surface functionality supporting iron/nickel bisalloy (FeNi@CMFs) have been successfully prepared in a single step by electrospinning combined with high temperature annealing method at an optimal condition: 5 wt% mass fractions of metal salts (ferric nitrate and nickel nitrate) annealed at 800 °C for 60 min in 5% (v/v) hydrogen/argon atmosphere. By simply controlling the microstructures and surface functional groups of CMFs in FeNi@CMFs through mass fractions of metal salts, annealing temperature and annealing time, FeNi@CMFs could acquire an outstanding ability to efficiently reduce hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) by iron/nickel bisalloy and simultaneously adsorb Cr(III) by carboxyl groups on the CMFs through chelation. The Cr(VI) removal by FeNi@CMFs follows the pseudo-second-order model. In thermodynamics, the negative ΔG0 and positive ΔH0 reveal that the Cr(VI) removal by FeNi@CMFs is a spontaneous and endothermic process, meaning that the increase in temperature is favorable for the Cr(VI) removal. Consequently, FeNi@CMFs are a kind of novel and efficient materials for Cr(VI) remediation.

Adsorption and recovery of hexavalent chromium from tannery wastewater over magnetic max phase composite

ABSTRACT Magnetic max phase composite (MNPs- Ti3AlC2) was synthesized in the laboratory and used for the adsorption and recovery of hexavalent chromium from Tannery wastewater. Maximum adsorption of Cr (IV), about 99% was found to occur at pH 3, 100 mg adsorbent dose for 30 mL sample and 5 min vortex time in presence of various competing ions. About 98 ± 1 % of Cr (IV) was easily recovered from the adsorbent surface by alkaline leaching. The adsorption process was found to bespontaneous, endothermic, and followed pseudo second order kinetics. Longmuir and Freundlich isotherms models were also applied to the adsorption data.

Single stage extraction and recovery of hexavalent chromium using blended TOA-TOMAC in palm oil-based diluent via supported liquid membrane process

Diluent is an important components in the supported liquid membrane (SLM) process. The conventional diluents used in SLM are usually flammable, volatile, and toxic. To promote a sustainable development, the palm oil was incorporated in the SLM for the removal and recovery of chromium. SLM is a three-phase system with an organic phase containing the carrier in diluent which immobilized in a membrane support and is set in between the simulated chromium and sodium hydroxide solutions that act as a feed and stripping phases respectively. Both solutions were pumped into the membrane support cell in a recycled operation for about 5 hours. To monitor the changes of the chromium ion concentration for both phases, the chromium ion concentration in the feed and stripping phases as a function of time was analysed using an atomic absorption spectrometry (AAS). Several parameters namely type of stripping agent, diluent composition and carrier concentration were investigated. Results showed that about 75 and 73% of chromium was extracted and recovered, respectively at the best conditions of using sodium hydroxide, mixture of palm oil-kerosene (50:50) and TOA-TOMAC (0.20-0.20M). Thus, palm oil is regarded as feasible as a greener diluent in SLM process for chromium ion extraction.

Bacteria cell templated porous polyaniline facilitated detoxification and recovery of hexavalent chromium

Increased porosity and H+ storage capacity by the bacteria templated-PANI facilitate improved Cr(vi) detoxification and subsequent recovery.

Nanoporous carbon synthesized from grass for removal and recovery of hexavalent chromium

Nanoporous carbon structures were synthesized by pyrolysis of grass as carbon precursor. The synthesized carbon has high surface area and pore volume. The carbon products were acid functionalized and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller, transmission electron microscopy, and Energy Dispersive X-ray microanalysis. Acid functionalized nanoporous carbon was explored for use in removal of toxic Cr(VI) ions from aqueous media. An adsorption study was done as a function of initial concentration, pH, contact time, temperature, and interfering ions. The experimental equilibrium data fits well to Langmuir isotherm model with maximum monolayer adsorption capacity of 35.335 mg/g. The results indicated that removal obeys a pseudo-second-order kinetic model, and that equilibrium was reached in 10 min. A desorption study was done using NaOH. The results of the present study imply that acid functionalized nanoporous carbon synthesized from grass is an efficient, renewable, cost-effective adsorbent material for removal of hexavalent chromium due to its faster removal rate and reusability.

Removal and Recovery of Cr(VI) from Industrial Plating Wastewater Using Fibrous Anion Exchanger

The aim of this study was to investigate the removal and recovery of hexavalent chromium (Cr(VI)) from industrial plating wastewater using anion exchanger Kanecaron SA fibers in batch systems. The surface morphology and physicochemical properties of the fiber were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDAX), and Fourier transform infrared spectroscopy (FT-IR). The removal efficiency was affected by the solution pH and showed a plateau formation decreasing on both sides of pH 4. The Cr(VI) uptake on Kanecaron SA fibers was rapidly increased in the first 10 min, and the kinetic data fit well to the Elovich model. Isotherm model analysis demonstrates that the Redlich-Peterson model suitably describes the equilibrium data, and the maximum adsorption capacity (Qm) from the Langmuir model was 87.366 mg/g for Cr(VI) in distilled water, 117.977 mg/g for total Cr, and 57.101 mg/g for Cr(VI) in wastewater. Additionally, the Cr(III) contained in the plating wastewater was removed by the Kanecaron SA fibers, while the other heavy metals were not removed. Thermodynamic analysis indicates that Cr(VI) adsorption to Kanecaron SA fibers decreased with increasing temperature from 10 to 50 °C, indicating the spontaneous and exothermic nature of the sorption process. The removal efficiency was maintained above 80 % during four regeneration cycles.

Recovery of hexavalent chromium from water using photoactive TiO2-montmorillonite under sunlight

Hexavalent chromium was removed from water under sunlight using a synthesized TiO 2 -montmorillonite (TiO 2 -M) employing tartaric acid as a hole scavenger. Cr(VI) species was then reduced to Cr(III) species by electrons arising from TiO 2 particles. After that, the produced Cr(III) species was transferred to montmorillonite due to electrostatic attractions leading to set free TiO 2 particles for a further Cr(VI) species reduction. Furthermore, produced Cr(III), after Cr(VI) reduction, does not penetrate into the solution. The results indicate that no dark adsorption of Cr(VI) species on TiO 2 -M is present, however, the reduction of Cr(VI) species under sunlight increased strongly as a function of tartaric acid concentration up to 60 ppm, for which the extent of reduction is maximum within 3 h. On the other hand, the reduction extent of Cr(VI) species is maximum with an initial concentration of Cr(VI) species lower than 30 ppm by the use of 0.2 g/L of TiO 2 -M. Nevertheless, the increase of the Cr(VI) initial concentration led to increase the amount of Cr(VI) species reduced (capacity of reduction) until a Cr(VI) concentration of 75 and 100 ppm, for which it remained constant at around 221 mg/g. For comparison, the increase of Cr(VI) species concentration in the case of the commercial TiO 2 P25 under the same conditions exhibited its deactivation when the reduced amount decreased from 198.1 to 157.6 mg/g as the concentration increased from 75 to 100 ppm.

Reduced graphene oxide based a novel polymer inclusion membrane: Transport studies of Cr(VI)

In this study, the removal and recovery of hexavalent chromium using reduced graphene oxide based polymer inclusion membrane from chrome plating water was investigated. The prepared modified membrane improved the mechanical properties and permeability of polymer inclusion membrane. Important outcomes of this study are high permeability, seamless porous structure, high selectivity and development of the polymer inclusion membrane by minimized nano-reinforced against pollution in addition of the unique physical properties of graphene oxide. The effects of carrier concentration, plasticizer type and temperature on the transport, the membrane's stability and thickness were examined. The polymer inclusion membrane was characterized by using atomic force microscopy, X-photo electron spectroscopy and contact angle measurements. The transport efficiency of Cr(VI) from chrome plating bath water was found to be 100% under optimized conditions. The experimental results showed that reduced graphene oxide modified polymer inclusion membrane exhibits great stability and selectivity in the presence of other metal cations in chrome plating bath water for the removal of Cr(VI).

Tetrahydrofuran (THF)-assisted alkaline extraction to determine hexavalent chromium (Cr(vi)) in retardant polymers containing Sb(iii)

THF-assisted alkaline extraction method was developed to overcome low recovery of hexavalent chromium (Cr(VI)) in polymers due to the reduction to Cr(iii) by Sb(iii).

Effect of solvent type on removal and recovery of hexavalent chromium from industrial wastewaters

Metals, especially chromium exists in a wide range of concentrations in natural water and wastewaters from various industrial operations. Reactive liquid extraction can be used for removing chromium. In this report, equilibrium experiments are presented on the removal of hexavalent chromium (Cr(VI)) using Aliquat 336 in various non-traditional solvents. The solvents are sunflower oil (fresh and recycled) and lubricating oil (fresh and recycled). The results are presented for the removal of Cr(VI) from aqueous solutions in the concentration range 0.5–500 ppm using Aliquat 336 (in the range 1.0–20% (v/v)). It is shown that sunflower oil and lubricating oil, both in the fresh and recycled forms, are able to remove Cr(VI) from ground waters and industrial wastewaters at their natural pH (range 6–8). These solvents gave satisfactory percentage extractions, producing water that can be recycled and they also offer advantages from health and safety, and environmental points of view. The results of the re-extraction process using KCl, K2CO3 and seawater are also presented. Seawater at its natural pH of 8 has shown potential for re-extraction. The findings have been applied to remove Cr(VI) from complex industrial wastewaters. The results provide good guidelines to the development of Cr(VI) removal and recovery processes using renewable, biodegradable, safe and cheap solvent systems demonstrated in this paper.

Microbial Detoxification of Hexavalent Chromium from Chromium-Containing Slag

In this paper,treatment and recovery of hexavalent chromium(Cr(Ⅵ)) from chromium-containing slag by bacteria was studied.The work showed that a bacterial strains of Ch-1 isolated from chromium-containing slag can efficiently accelerate Cr(Ⅵ) leaching and remove it.Moreover,bacteria Ch-1 can effectively change the structure of chromium-containing slag by Scanning Electron Microscopy(SEM) and the Energy Dispersive X-Ray(EDX),which is benefitial to Cr(Ⅵ) leaching and its detoxification by changing Cr(Ⅵ) to Cr(Ⅲ).The effect of detoxification by bacteria of Ch-1 is obvious,the toxicity in leached slag was 3.3 μg/g lower than the national standard of 5 μg/g,and the recovery rates of hexavalent chromium are more than 90%.

Hexavalent chromium recovery by liquid–liquid extraction with 2-octylaminopyridine from acidic chloride media and its sequential separation from other heavy toxic metal ions

A systematic study of extraction of chromium(VI) with 2-octylaminopyridine (2-OAP) in xylene at room temperature has been conducted. Quantitative extraction of chromium(VI) was observed in the 0.4–0.8M concentration range of hydrochloric acid. From the extracted complex species in the organic phase, chromium(VI) was back extracted with 7N ammonia (3×10mL), and was determined by spectrophotometric method. Various parameters such as 2-OAP concentration, equilibrium period, effect of various diluents, aqueous: organic volume ratio, acidity and diverse ions were studied. The extraction reaction proceeds with ion-pair formation and the stoichiometry of extracted species was found to be [(2OAPH+) CrO3Cl−](org). The separation and determination of chromium(VI) from associated and toxic metals in binary, ternary and multicomponent mixture were carried out. The method permits the sequential separation of chromium(VI) from other toxic metals and has been used to separate and determine chromium(VI) from alloys, and effluent water samples from tannery industries.

Hexavalent Chromium Recovery by Electrochemical Reactor of Ceramic Spacers Compartments Separated by Potentiostat Operating Mode

The key parameters in the control of an electrochemical reactor in operation are the potential of working electrode and the current distribution, which depend on many factors, among which include: the transfer, the hydrodynamic conditions and the total voltage of the cell, Uc. However, it is often impossible to monitor these parameters and we must resort to measure other parameters such as total intensity, (the electrode potential) and the total voltage of the cell. Thus in the control of an electrochemical reactor (or the operation of an electrochemical reactor) can be carried out by controlling one of three variables: the electrode potential, voltage or current total. In this paper works in potenctiostat mode determined the main parameters or figures of merit that characterize this type of reactor, which is designed first and then at laboratory pilot scale

Feasibility study on the recovery of hexavalent chromium from a simulated electroplating effluent using Alamine 336 and refined palm oil

Chromium is an element that is widely used in stainless steel manufacturing, leather tanning and electroplating. Its hexavalent species are toxic and cause of considerable damage if released into the environment. Coupled with depleting reserves and stricter environmental laws it becomes necessary to reduce, reuse and recycle this important commodity. The objective of the study is to test the suitability of Alamine 336 and a renewable and biodegradable diluent, i.e. refined palm oil, in the recovery of hexavalent chromium from synthetic concentrated electroplating effluents using the anionic liquid ion exchange (ALIX) process. The performance of refined palm oil was compared with kerosene, a flammable nonbiodegradable commercial solvent. Alamine 336:diluent molar ratios of up to 1:1 can be carried out with refined palm oil over a pH range of 1–4 with a single-step extraction efficiency of up to 95%. Speciation modelling with Visual MINTEQ ® suggests a high Alamine 336 affinity for hexavalent chromium species CrO 3SO 4 2− and HCrO 4 −. The presence of interfering metal ions like iron and zinc slightly suppressed the chromium uptake capability of Alamine 336. Sulphate anions, as well as the presence of copper and nickel ions have no negative effect on Cr(VI) extraction. Visual MINTEQ ® has proven to be a useful tool in solving relatively complex metal speciation and solubility problems encountered in ALIX extraction. The findings of this study provide a significant step towards a greener and safer chromium recovery process in the electroplating industry but also commercial and academic analytical laboratories.

Studies on recovery of hexavalent chromium from plating wastewater by supported liquid membrane using tri- n-butyl phosphate as carrier

The transport of chromium(VI) ions from an aqueous feed solution through a flat type supported liquid membrane (SLM) containing tri- n-butyl phosphate (TBP) as carrier was studied. The influence of pH on the source phase, effect of concentration of receiving phase, stirring speed, effect of initial Cr(VI) concentration, feed to strip ratio and the influence of support characteristics was studied. Polytetrafluoroethylene (PTFE) with 1.0 μm pore size was found to have more flux permeability than 0.50 μm. The results indicated that the aqueous feed solution at pH 1 ± 0.1 to have high permeability. The initial feed phase Cr(VI) concentration of 9.6 × 10 − 4 M can be completely extracted and stripped with 0.50 M sodium hydroxide as stripping solution within 8 h. Stirring of aqueous solutions at 500 rpm with a magnetic stirrer showed high transport rate. After ten transport studies with one impregnation of carrier, the TBP carrier showed no significant loss in its permeability and retained the same transport ability. Under the optimum conditions chromium(VI) recovery from real plating wastewater was tested and found to be satisfactory with a flux value of 1.4 × 10 − 3 mol/m 2/s.

Hexavalent chromium recovery by liquid-liquid extraction with tributylphosphate from acidic chloride media.

A method is introduced for recuperation of chromium(VI) in water samples by liquid-liquid extraction with tributylphosphate PO(C4H9O)3 (TBP) from acidic chloride media. The optimum conditions for quantitative extraction of Cr(VI) were evaluated by varying the experimental parameters, such as the shaking period, the pH of the aqueous phase, the hydrochloric acid concentration, the hydrogen and chloride ion concentrations, the extractant concentration and the ratio of aqueous-to-organic phase. The probable extracted species of hexavalent chromium in organic phase, deduced from log-log plots, were H2CrO4 in acid media in absence of chloride and HCrO3Cl in acidic chloride media. Chromium(VI) was found to be extracted with tributylphosphate from acidic chloride media according to the following reaction: HCrO4-(aq), + 2H+(aq) + Cl-(aq) + 2TBP(org) <==> [HCrO3Cl, 2TBP](org) + H2O(aq). Since the tributylphosphate (TBP) exhibited a high selectivity for chromium(VI), this method can be applicable to the extraction and the determination of chromium in both oxidation states [Cr(VI) and Cr(III)] in water samples.

Optimal design of membrane processes for wastewater treatment and metal recovery

Different continuous operating modes of a nondispersive solvent extraction (NDSX) process with membrane modules of hollow fibre for wastewater treatment and metal recovery are evaluated. Cocurrent and countercurrent flow of aqueous and organic phases in the membrane modules with alternative product extraction locations for the removal and recovery of hexavalent chromium from wastewater are studied. The design of NDSX process in a countercurrent continuous operation is addressed for the first time in this work and the improvement achieved is reported. The membrane area required in the countercurrent operation is reduced significantly compared with the cocurrent operation, requiring also less investment in pumps and pumping cost leading to the minimum total cost. Thus a significant improvement in the design of this new and cleaner technology is presented.