Chromium Binding Research Articles

Application of Chattim tree (devil tree, Alstonia scholaris) saw dust as a biosorbent for removal of hexavalent chromium from contaminated water

Abstract“Devil tree saw dust”; a novel biosorbent has been utilised successfully for the removal of hexavalent chromium from contaminated water. Batch adsorption procedure is utilised to test the ability of saw dust as an adsorbent for hexavalent chromium (reduction coupled adsorption). The contribution of various parameters on sorption, such as contact time, sorbate concentration, pH of the medium and temperature were estimated and maximum uptake of hexavalent chromium from contaminated water was 333.33 mg g−1 at pH 2.0 and temperature of 35°C. Hexavalent chromium uptake from contaminated water followed the pseudo‐first‐order rate expression. The standard free energy change (ΔG0), standard enthalpy change (ΔH0) and standard entropy change (ΔS0) have also been evaluated and it has been concluded that the sorption was feasible, spontaneous and endothermic in nature. The process follows well Langmuir isotherm. Fourier Transform Infra‐Red (FTIR) spectroscopy and scanning electron microscopy (SEM) of hexavalent chromium loaded and unloaded saw dust were performed, SEM clearly indicates chromium adsorption. FTIR spectroscopy revealed the involvement of carbonyl, hydroxyl and amide groups on the cell surfaces in chromium binding. Very good adsorption capacity and low cost or cost free of devil tree saw dust makes this biosorbent as one of the best adsorbents for removal of hexavalent chromium from contaminated water. © 2012 Canadian Society for Chemical Engineering

Hexahapto‐Metal Complexes of Single‐Walled Carbon Nanotubes

AbstractWe report the preparation of organometallic side‐wall complexes of single‐walled carbon nanotubes (SWNTs) under conditions, which allow the study of both mono‐ and bis‐hexahapto SWNT coordination compounds [(η6‐SWNT)Cr(CO)3, (η6‐SWNT)Cr(η6‐C6H6), (η6‐SWNT)2Cr]. The results are interpreted in terms of exohedral and endohedral binding of chromium to the SWNT sidewalls and ligand competition reactions suggest that endohedral binding provides a very stable and kinetically inert mode of organometallic bonding. We demonstrate that the electrical conductivity of SWNT thin films are significantly enhanced by side‐wall bonding to Group 6 transition metals (M = Cr, Mo, and W), which serve to reduce the inter‐carbon nanotube junction electrical resistance by the formation of SWNT interconnects [(η6‐SWNT)2M].

A spectroscopic study for understanding the speciation of Cr on palm shell based adsorbents and their application for the remediation of chrome plating effluents

Palm shell based adsorbents prepared under five different thermochemical conditions have been shown to be quite effective for removal of chromium (III and VI) from aqueous solutions. X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FT-IR) have been used to determine information about the speciation and binding of chromium on the adsorbents under study. X-ray photoelectron spectroscopy (XPS) studies indicate that oxidation of lignin moieties takes place concurrently to Cr(VI) reduction and leads to the formation of hydroxyl and carboxyl functions. The maximum adsorption capacity for hexavalent chromium was found to be about 313mg/g in an acidic medium using PAPSP. This is comparable to other natural substrates and ordinary adsorbents. The efficacy of the adsorbents under study to remove chromium from plating waste water has been demonstrated.

Comparative kinetics, equilibrium, thermodynamic and mechanistic studies on biosorption of hexavalent chromium by live and heat killed biomass of Acinetobacter junii VITSUKMW2, an indigenous chromite mine isolate

The current study focuses on the quantification and mechanistics of Cr(VI) biosorption with Acinetobacter junii, indigenous bacteria isolated from chromite mine sites of Sukinda valley, Orissa, India. The equilibrium sorption capacity 22.22, 13.88, 6.94mg of Cr(VI)g−1 of biomass was obtained for logarithmic phase, stationary phase and heat killed biomass respectively at optimum sorption conditions (pH: 2.0, contact time: 120min, temperature: 27°C, initial Cr(VI) concentration: 100mgL−1, biosorbent dosage: 2gL−1). The Langmuir isotherm model and pseudo first order (Lagergren kinetic model) were observed to hold good for the bio-sorbents. Three subsequent sorption/desorption cycles yielded 54.9, 38.4 and 34.5% regeneration of the biosorbent indicating an irreversible chromium(VI) binding property of the sorbent system. The mechanistic aspects of sorption by heat killed and log phase biomass were compared using FTIR and SEM techniques. The number of binding sites on biomass surface measured by acid/base titration (215μmolg−1 and 99μmolg−1 for logarithmic phase and heat killed biomass respectively) corroborated with the observations made by batch sorption studies. Detailed surface characterization studied through FT-IR, SEM, EDX and zeta potential measurement provided evidence for sorption through oxyanionic binding to the cell surface. The EPR spectroscopy revealed the reduction of Cr(VI) to Cr(V) on the biomass surface upon Cr(VI) sorption.

Biosorption and biotransformation of chromium by Serratia sp. isolated from tannery effluent

A bacterium isolated from soil and sediment of a leather tanning mill's effluent was identified as Serratia sp. by the analysis of 16S rDNA. Scanning electron microscopy–energy dispersive X-ray analysis (SEM-EDX) and transmission electron microscopy (TEM) were used to assess morphological changes and confirm chromium biosorption in Serratia sp. both in a shake-flask culture containing chromium and in a tannery wastewater. The SEMEDX and the elemental analysis of the chromate-containing samples confirmed the binding of chromium with the bacterial biomass. The TEM exhibited chromium accumulation throughout the bacterial cell, with some granular deposits in the cell periphery and in the cytoplasm. X-ray diffraction analysis (XRD) was used to quantify the chromium and to determine the chemical nature of the metal–microbe interaction. The XRD data showed the crystalline character of the precipitates, which consisted of mainly calcium chromium oxide, chromium fluoride phosphate and related organo-Cr(III) complex crystals. The XRD data also revealed a strong involvement of cellular carboxyl and phosphate groups in chromium binding by the bacterial biomass. The results of the study indicated that a combined mechanism of ion-exchange, complexation, croprecipitation and immobilization was involved in the biosorption of chromium by bacterial cells in contaminated environments.

Biosorption of chromium (Cr(III)/Cr(VI)) on the residual microalga Nannochloris oculata after lipid extraction for biodiesel production

In order to increase the economic feasibility of biodiesel production from microalgae, the residual biomass after biodiesel production can be utilized as biosorbent for heavy metal removal. In this study, biosorption of chromium by residual Nannochloris oculata after lipid extraction was investigated. Increased surface area of N. oculata was observed after lipid extraction. Cr(III) removal increased as the pH increased from 2 to 6, while Cr(VI) removal was highest at pH 2 and it decreased with the increase in pH. Cr(VI) was reduced to Cr(III) in the presence of biomass under acidic conditions; X-ray photoelectron spectroscopy revealed that the converted Cr(III) was bound to the biomass. Chromium removal was significantly enhanced at high chromium concentrations, which indicates that surface reactions may occur at high chromium/biomass ratios. FTIR study indicated that phosphate and carboxyl functional groups of the biomass were mainly responsible for chromium binding.

Study of Cr(III) desorption process from a water-soluble polymer by ultrafiltration

Polymer Enhanced Ultrafiltration (PEUF) has been reported as a suitable process to separate heavy metals from pollutant wastewaters. Desorption of metal ion is a required step in order to recycle the polymer. At acidic pH values, nearly quantitative desorption has been achieved for divalent ions but a limited efficiency has been reached for trivalent ions. This paper studies the Cr(III) desorption yield from ethoxylated polyethylenimine (EPEI) by means of an ultrafiltration ceramic membrane. Experimental results show that about only 20% of the chromium (III) remains adsorbed at pH 1. The feasibility of several sorption isotherms (Langmuir, Freundlich, Redlich–Peterson and Temkin) was tested to describe the binding of chromium (III) and EPEI and the Freundlich one showed the best fits with experimental data at all pH values. Further, it was observed that normalized permeate fluxes decreased as initial Cr(III) concentration and pH were higher. Membrane fouling was analyzed by long–term experiments at different pHs which indicate that the intermediate pore blocking was the main mechanism of fouling.

Characterization of the Organic Component of Low-Molecular-Weight Chromium-Binding Substance and Its Binding of Chromium

Chromium was proposed to be an essential element over 50 y ago and was shown to have therapeutic potential in treating the symptoms of type 2 diabetes; however, its mechanism of action at a molecular level is unknown. One chromium-binding biomolecule, low-molecular weight chromium-binding substance (LMWCr or chromodulin), has been found to be biologically active in in vitro assays and proposed as a potential candidate for the in vivo biologically active form of chromium. Characterization of the organic component of LMWCr has proven difficult. Treating bovine LMWCr with trifluoroacetic acid followed by purification on a graphite powder micro-column generates a heptapeptide fragment of LMWCr. The peptide sequence of the fragment was analyzed by MS and tandem MS (MS/MS and MS/MS/MS) using collision-induced dissociation and post-source decay. Two candidate sequences, pEEEEGDD and pEEEGEDD (where pE is pyroglutamate), were identified from the MS/MS experiments; additional tandem MS suggests the sequence is pEEEEGDD. The N-terminal glutamate residues explain the inability to sequence LMWCr by the Edman method. Langmuir isotherms and Hill plots were used to analyze the binding constants of chromic ions to synthetic peptides similar in composition to apoLMWCr. The sequence pEEEEGDD was found to bind 4 chromic ions per peptide with nearly identical cooperativity and binding constants to those of apoLMWCr. This work should lead to further studies elucidating or eliminating a potential role for LMWCr in treating the symptoms of type 2 diabetes and other conditions resulting from improper carbohydrate and lipid metabolism.

Role of microbial exopolymeric substances (EPS) on chromium sorption and transport in heterogeneous subsurface soils: I. Cr(III) complexation with EPS in aqueous solution

Chromium (III) binding by exopolymeric substances (EPS) isolated from Pseudomonas putida P18, Pseudomonas aeruginosa P16 and Pseudomonas stutzeri P40 strains were investigated by the determination of conditional stability constants and the concentration of functional groups using the ion-exchange experiments and potentiometric titrations. Spectroscopic (EXAFS) analysis was also used to obtain information on the nature of Cr(III) binding with EPS functional groups. The data from ion-exchange experiments and potentiometric titrations were evaluated using a non-electrostatic discrete ligand approach. The modeling results show that the acid/base properties of EPSs can be best characterized by invoking four different types of acid functional groups with arbitrarily assigned p K a values of 4, 6, 8 and 10. The analysis of ion-exchange data using the discrete ligand approach suggests that while the Cr binding by EPS from P. aeruginosa can be successfully described based on a reaction stoichiometry of 1:2 between Cr(III) and HL 2 monoprotic ligands, the accurate description of Cr binding by EPSs extracted from P. putida and P. stutzeri requires postulation of 1:1 Cr(III)-ligand complexes with HL 2 and HL 3 monoprotic ligands, respectively. These results indicate that the carboxyl and/or phosphoric acid sites contribute to Cr(III) binding by microbial EPS, as also confirmed by EXAFS analysis performed in the current study. Overall, this study highlights the need for incorporation of Cr–EPS interactions into transport and speciation models to more accurately assess microbial Cr(VI) reduction and chromium transport in subsurface systems, including microbial reactive treatment barriers.

Synthesis of polypyrrole nanoparticles and its grafting with silica gel for selective binding of chromium(VI)

Polypyrrole nanoparticles of desired structure have been synthesized through simple micelle technique. It is then grafted with functionalized silica gel to develop a novel organic–inorganic hybrid material. The role of dimethyl dichloro silane (coupling agent) in grafting is demonstrated. The nanoparticles are characterized by TEM, SEM and TGA. Grafting reactions are evaluated by spectral (FTIR) analysis and chemical test. The Cr(VI) binding behavior of the composite is studied in various pH of the medium. The selectivity in binding Cr(VI) is monitored. The metal ion adsorption capacity and surface area of the material are found to be 38mg/g and 235m2/g, respectively.

Removal of Cr(VI) from aqueous solution by fungal biomass

AbstractChromium compounds are released by industrial processes including leather production, mining, petroleum refining, in textile industry and dyeing. They are a significant threat to the environment and public health because of their toxicity. Removal of hexavalent chromium by living biomass of different fungi was effective in the order of Aspergillus terricola>Aspergillus niger>Acremonium strictum>Aureobasidium pullulans>Paecilomyces variotii>Aspergillus foetidus>Cladosporium resinae>Phanerochaete chrysosporium. Non‐living dried fungal biomass showed higher potential for metal removal than living cells. Among all fungi dead biomass of P. chrysosporium, C. resinae and P. variotii had the maximum specific chromium uptake capacity, which was 11.02, 10.69 and 10.35 mg/g of dry biomass respectively at pH 4.0–5.0 in batch sorption. Removal of Cr(VI) by P. chrysosporium from multi‐metallic synthetic solution as well as chrome effluent was significant by bringing down the residual concentration to 0.1 mg/L in the effluent, which falls within the permissible range and its removal was not affected by the presence of other metal ions such as Fe, Zn and Ni. Fourier transform infrared spectral analysis revealed the presence of carboxylate (C=O) and amine (−NH, −NH) functional groups commonly present on the cell surface of all fungi, with possible involvement in chromium binding. The result indicates that non‐living fungal biomass either obtained as a by‐product of fermentation industry or mass produced using inexpensive culture media can be used for bioremediation of Cr(VI) from chrome effluent on large scale.

Imaging Metals in Proteins by Combining Electrophoresis with Rapid X-ray Fluorescence Mapping

Growing evidence points toward a very dynamic role for metals in biology. This suggests that physiological circumstance may mandate metal ion redistribution among ligands. This work addresses a critical need for technology that detects, identifies, and measures the metal-containing components of complex biological matrixes. We describe a direct, user-friendly approach for identifying and quantifying metal-protein adducts in complex samples using native- or SDS-PAGE, blotting, and rapid synchrotron X-ray fluorescence mapping with micro-XANES (X-ray absorption near-edge structure) of entire blots. The identification and quantification of each metal bound to a protein spot has been demonstrated, and the technique has been applied in two exemplary cases. In the first, the speciation of the in vitro binding of exogenous chromium to blood serum proteins was influenced markedly by both the oxidation state of chromium exposed to the serum proteins and the treatment conditions, which is of relevance to the biochemistry of Cr dietary supplements. In the second case, in vivo changes in endogenous metal speciation were examined to probe the influence of oxygen depletion on iron speciation in Shewanella oneidensis.

Characterization and comparison of chitosan/PVP and chitosan/PEO blend films

The objective of this study was to investigate and compare the physical and functional properties of chitosan films prepared with poly (N-vinyl-2-pyrrolidone) (PVP) and polyethylene oxide (PEO). Addition of PVP or PEO reduced yellowish coloration of chitosan-based films and made the films easier to puncture and tear. Contrary to chitosan/PEO films, where addition of PEO had tendency to reduce water vapor permeability (WVP), the chitosan/PVP films with PVP content of 75% had significantly higher WVP compared to pure chitosan films. Chromium binding capacity of the films was not significantly reduced by any of the tested synthetic polymers even when they replaced up to 75% chitosan in the films. Similarly, antimicrobial efficiency was reduced only when 75% PEO or 50% PVP was used in the films. It appears that incorporation of PVP or PEO in chitosan films could significantly reduce production price with no effect on functionality of the films.

Nanofibrous chitosan non-wovens for filtration applications

Abstract Chitosan containing nanofibrous filter media has the advantage of filtering material based on both its size and functionality. They can be potentially applicable in a wide variety of filtration applications ranging from water purification media to air filter media. We have fabricated nanofibrous filter media by electrospinning of chitosan/PEO blend solutions onto a spunbonded non-woven polypropylene substrate. Filter media with varying fiber diameter and filter basis weight were obtained. Heavy metal binding, anti-microbial and physical filtrations efficiencies of these chitosan based filter media were studied and correlated with the surface chemistry and physical characteristics of these nanofibrous filter media. Filtration efficiency of the nanofiber mats was strongly related to the size of the fibers and its surface chitosan content. Hexavalent chromium binding capacities up to 35 mg chromium/g chitosan were exhibited by chitosan based nanofibrous filter media along with a 2–3 log reduction in Escherichia coli bacteria cfu.

Removal of chromium (VI) ions from aqueous solution by adsorption onto two marine isolates of Yarrowia lipolytica

The removal of chromium (VI) ions from aqueous solutions by the biomass of two marine strains of Yarrowia lipolytica (NCIM 3589 and 3590) was studied with respect to pH, temperature, biomass, sea salt concentration, agitation speed, contact time and initial concentration of chromium (VI) ions. Maximum biosorption was observed at pH 1.0 and at a temperature of 35 °C. Increase in biomass and sea salts resulted in a decreased metal uptake. With an agitation speed of 130 rpm, equilibrium was attained within 2 h. Under optimum conditions, biosorption was enhanced with increasing concentrations of Cr (VI) ions. NCIM 3589 and 3590 displayed a specific uptake of Cr (VI) ions of 63.73 ± 1.3 mg g −1 at a concentration of 950 ppm and 46.09 ± 0.23 mg g −1 at 955 ppm, respectively. Scatchard plot analysis revealed a straight line allowing the data to be fitted in the Langmuir model. The adsorption data obtained also fitted well to the Freundlich isotherm. The surface sequestration of Cr (VI) by Y. lipolytica was investigated with a scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS) as well as with ED-X-ray fluorescence (ED-XRF). Fourier transform infrared (FTIR) spectroscopy revealed the involvement of carboxyl, hydroxyl and amide groups on the cell surfaces in chromium binding.

The New Application of Biosorption Properties of Enteromorpha prolifera

The main goal of this paper was to elaborate the possibility of industrial application of biosorption properties of Enteromorpha prolifera (production of mineral feed additives for livestock). In this study, biosorption process was used in the binding of chromium(III) ions from aqueous solution by the green macroalga. The kinetics of biosorption process was studied in a batch system with respect to the initial pH, temperature, initial metal ion concentration, and initial biomass concentration. E. prolifera demonstrated good biosorption properties. The equilibrium biosorption capacity increased with pH and with initial concentration of metal ions. The uptake of chromium(III) ions by the dried alga was affected by the temperature, but in small extent. With increase of the biomass concentration, the decrease of biosorption capacity at equilibrium was observed. The best biosorption conditions were determined as the initial pH 5, temperature 25 degrees Celsius, the initial chromium(III) ions concentration 400 mg/L, and biosorbent concentration 1.0 g/L. Biosorption capacity at equilibrium reached at these conditions was 100 mg/g. The mechanism of the biosorption of chromium(III) ions by E. prolifera was analyzed in equilibrium experiments. Equilibrium data were fitted to Langmuir, Dubinin-Radushkevich, and Freundlich adsorption isotherms. The most suitable model for describing the obtained data was Langmuir model. The experimental results and the analysis of the solution before and after biosorption process suggested ion-exchange mechanism.

Fungal bioremediation of chromates: Conformational changes of biomass during sequestration, binding, and reduction of hexavalent chromium ions

This paper highlights the mechanistic aspects of white rot fungus Coriolus versicolor as a complexing/reducing agent for chromium bioremediation. The chemical reduction of Cr(VI) to Cr(III) via the formation of Cr(VI) thio ester as an intermediate, is pH dependent and controls the overall chromium adsorption kinetics. The strong adsorption affinity of the biomass towards Cr(VI) anions was evaluated by the Freundlich and the Langmuir adsorption isotherms. The FTIR spectroscopic analysis suggested the involvement of amino, carboxylate, and thiol groups from fungal cell wall in chromium binding and reduction. The mechanism of the adsorption was preferential sequestration along with binding of the metal to the ligating groups present in the biomass followed by reduction to trivalent state. The results indicate step-wise progression of overall reaction dictated and modulated by structural and conformation effects in the biomass that lead to saturation, acceleration, and ultimate saturation kinetics effects.

Removal of Cr(VI) from aqueous solution using Bael fruit ( Aegle marmelos correa) shell as an adsorbent

In this study, a new activated carbon prepared from non-usable Bael fruit shell (BS) has been used as an efficient low cost adsorbent to remove the Cr(VI) toxic metal from aqueous phase. Batch mode experiments have been performed as a function of initial pH of solution, agitation time, adsorbate concentration and adsorbent dosage. Maximum chromium removal was found at pH 2.0 in an equilibrium time of 240 min by adsorption-coupled reduction. The sorption data fitted satisfactorily with Langmuir as well as Freundlich adsorption model. Evaluation using Langmuir equation gave the monolayer sorption capacity as 17.27 mg/g. Chromium uptake (adsorption-coupled reduction) by Bael fruit shell activated carbon (BSAC) was best described by pseudo-second-order chemisorption model. The progressive changes on surface texture and the confirmation of chromium binding on adsorbent surface at different stages were obtained by the scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectrometer (FT-IR) analysis. Phosphoric acid activation played a significant role to develop the well defined pores on adsorbent surface. The results obtained in this study illustrate that the BSAC is expected to be an effective and economically viable adsorbent for Cr(VI) removal from aqueous system.

A novel study of hexavalent chromium detoxification by selected seaweed species using SEM-EDX and XPS analysis

Abstract The toxicity and mobility of Cr(VI) means that it is crucial that the amount of the heavy metal discharged in industrial waste streams is significantly decreased. Seaweed biomass represents a benign, cost-effective, sustainable and efficient solution for the detoxification of anionic Cr(VI) to the less hazardous cationic Cr(III). Chromium binding and reduction behaviour of three seaweeds, Fucus vesiculosus (brown), Ulva spp. (green) and Palmaria palmata (red), was investigated using a colorimetric method while the surface characteristics of the biomasses were examined using SEM/EDX and XPS techniques. This is the first study of red seaweeds for the detoxification of Cr(VI). Results indicated that F. vesiculosus and P. palmata had comparable total Cr removal efficiencies of approximately 18%, while Ulva spp. removed 14% Cr from a 2000 mg L −1 metal solution. Conversion of Cr(VI) to Cr(III) in solution ranged from 51% for F. vesiculosus to 34% for Ulva spp. over a 6-h period. SEM revealed considerable morphological differences between Cr(III) and Cr(VI)-loaded seaweeds while EDX results confirmed an ion-exchange mechanism for Cr(III) binding. XPS results indicated that significant quantities of Cr(VI) solution were reduced when placed in contact with the seaweed surface over a 6-h period, resulting in a 64–75% conversion to Cr(III) bound to the seaweed. Thus, the potential of these seaweeds to bio-reduce and detoxify elevated Cr(VI) concentrations over relatively short time periods has been demonstrated. Cr(VI) binding also altered the relative quantities of carboxyl and alcohol groups in biomass polysaccharides, thus indicating the importance of these functionalities in binding and reduction of Cr(VI) to Cr(III). This work, coupled with existing capacity data points towards the viability of these environmentally friendly biosorbents for use in packed columns in a number of industries including electroplating and tanning.

Interaction of Chromium with Resistant Strain Aspergillus versicolor: Investigation with Atomic Force Microscopy and Other Physical Studies

The interaction of chromium and a chromate resistant Aspergillus versicolor strain has been studied by atomic force (AFM) and transmission electron (TEM) microscopies. The nanomechanical properties such as cell wall rigidity and elasticity were measured by force spectroscopy and found to be 0.61 +/- 0.08 N/m, and 20.5 +/- 2.1 MPa, respectively. On chromium binding, ultrastuctural changes of the cell wall along with the formation of layered structures on the cell wall were observed. TEM and AFM micrographs demonstrate the accumulation of chromium on the cell wall, which were rough and irregular compared with the smooth pristine mycelia. The surface roughness, cell wall rigidity and elasticity increased to 35.5 +/- 3.5 nm, 0.88 +/- 0.05 N/m, and 62.5 +/- 3.5 MPa, respectively, from the corresponding values of 5.2 +/- 0.68 nm, 0.61 +/- 0.02 N/m, and 20.5 +/- 2.1 MPa for the pristine mycelia. X-ray photoelectron spectroscopy and Fourier transform infrared studies suggest that bound chromium was reduced to its trivalent state by the cell wall components. The reduced chromium species on the cell surface further electrostatically bind chromate ions forming layered structure on the cell wall.