Remediation Of Hexavalent Chromium Research Articles

Remediation of Cr (VI) by inorganic-organic clay

Application of inorganic–organic clays (IOCs) for the remediation of hexavalent chromium (Cr (VI)) and the effect of bisphenol-A (BPA) were investigated. IOCs were better adsorbents for the removal of Cr (VI) than organoclay. Solution pH significantly affected the surface charge of IOCs and speciation of Cr in the solution; hence, the adsorption of Cr onto IOCs. Pseudo-second order model and Langmuir model were the best fit for the kinetics and equilibrium data, indicating chemisorption and formation of monolayer on homogenous adsorption sites, respectively. Cr (VI) adsorption by IOCs was driven by electrostatic interactions between positively charged IOC surfaces and HCrO4- anions. The IOC adsorption capacity for Cr (VI) correlates with the amount of loosely held ODTMA on the external surface of the clay. Involvement of an anion-exchange reaction was suggested in which the counter halide ions of the cationic surfactants were replaced by HCrO4- anions. Cr (VI) adsorption was not affected by the presence of BPA in the medium and two mechanisms for the adsorption of BPA and Cr (VI) were suggested. Partial reduction of Cr (VI) to Cr (III) was observed on the surface of IOC and the reducing agent responsible was suggested to be the Fe (II) in montmorillonite.

Remediation of hexavalent chromium spiked soil by using synthesized iron sulfide particles

Carboxymethyl cellulose (CMC) stabilized microscale iron sulfide (FeS) particles were synthesized and applied to remediate hexavalent chromium (Cr(VI)) spiked soil. The effects of parameters including dosage of FeS particles, soil moisture, and natural organic matter (NOM) in soil were investigated with comparison to iron sulfate (FeSO4). The results show that the stabilized FeS particles can reduce Cr(VI) and immobilize Cr in soil quickly and efficiently. The soil moisture ranging from 40% to 70% and NOM in soil had no significant effects on Cr(VI) remediation by FeS particles. When molar ratio of FeS to Cr(VI) was 1.5:1, about 98% of Cr(VI) in soil was reduced by FeS particles in 3 d and Cr(VI) concentration decreased from 1407 mg kg−1 to 16 mg kg−1. The total Cr and Cr(VI) in Toxicity Characteristic Leaching Procedure (TCLP) leachate were reduced by 98.4% and 99.4%, respectively. In FeS particles-treated soil, the exchangeable Cr fraction was mainly converted to Fe-Mn oxides bound fraction because of the precipitation of Cr(III)-Fe(III) hydroxides. The physiologically based extraction test (PBET) bioaccessibility of Cr was decreased from 58.67% to 6.98%. Compared to FeSO4, the high Cr(VI) removal and Cr immobilization efficiency makes prepared FeS particles a great potential in field application of Cr(VI) contaminated soil remediation.

Chromium immobilization in soil using quaternary ammonium cations modified montmorillonite: Characterization and mechanism

The potential risk of heavy metal in soil can be reduced by stabilization techniques. Stabilizing amendments, montmorillonites modified with tetramethylammonium (TMA) and hexadecyltrimethylammonium (HDTMA) at different loadings were prepared, characterized and assayed for remediation of hexavalent chromium contaminated soil. Characterization results demonstrated that TMA modification resulted in increased surface area and pore volume, whereas HDTMA modification resulted in decreased surface area and pore volume. For HDTMA modified montmorillonites (H-Monts), the arrangement model of surfactant molecules and the structural characteristics strongly depended on the surfactant loading density. Less pronounced packing density dependence was observed for TMA modified montmorillonites (T-Monts). Modified toxicity characteristic leaching procedure (TCLP) was utilized to evaluate the chromium immobilizing capacity of the prepared organo-montmorillonites, and the results revealed that both T-Monts and H-Monts can be reasonably effective in chromium stabilization under different leaching condition. The comparison of chromium leaching behavior manifested by T-Monts and H-Monts suggested that mechanisms for chromium immobilization by organo-montmorillonites amendment proceeded via two adsorption approaches. Each approach involves different functional groups, depending on the leaching pH and surfactant loading concentration. In addition, the effect of HDTMA loading concentration, amendment dosage, initial chromium concentration and incubation time on the immobilizing efficiency of H-Monts was investigated.

Remediation of hexavalent chromium contaminated soil by biochar-supported zero-valent iron nanoparticles

In this study, a kind of high-efficiency and low-cost biochar-supported zero-valent iron nanoparticles (nZVI@BC) was synthesised and used in the remediation of Cr(VI)-contaminated soil. The remediation tests indicated that the immobilisation efficiency of Cr(VI) and Crtotal was 100% and 91.94%, respectively, by 8g nZVI@BC per kg soil for 15 d of remediation. Further investigations showed that exchangeable Cr was almost completely converted to Fe-Mn oxides and organic matter. Moreover, nZVI@BC could effectively improve soil fertility and reduce the leachability of Fe caused by nZVI. At the same time, the cabbage mustard growth experiments indicated that the phytotoxicity of Cr(VI) and Fe in the seedlings was effectively decreased by nZVI@BC treatment, and that the cabbage mustard growth was enhanced.

Bacteria-immobilized electrospun fibrous polymeric webs for hexavalent chromium remediation in water

The development of hexavalent chromium remediating fibrous biocomposite mats through the immobilization of a hexavalent chromium reducing bacterial strain, Morganella morganii STB5, on the surfaces of electrospun polystyrene and polysulfone webs is described. The bacteria-immobilized biocomposite webs have shown removal yields of 93.60 and 93.79 % for 10 mg/L, 99.47 and 90.78 % for 15 mg/L and 70.41 and 68.27 % for 25 mg/L of initial hexavalent chromium within 72 h, respectively, and could be reused for at least five cycles. Storage test results indicate that the biocomposite mats can be stored without losing their bioremoval capacities. Scanning electron microscopy images of the biocomposite webs demonstrate that biofilms of M. morganii STB5 adhere strongly to the fibrous polymeric surfaces and are retained after repeated cycles of use. Overall, the results suggest that reusable bacteria-immobilized fibrous biocomposite webs might be applicable for continuous hexavalent chromium remediation in water systems.

Potential of cobalt ferrite nanoparticles (CoFe2O4) for remediation of hexavalent chromium from synthetic and printing press wastewater

Cobalt ferrite (CoFe2O4) nanoparticles were successfully synthesized, characterized and utilized for the treatment of chromium containing synthetic wastewater and printing press wastewater. Characterization of CoFe2O4 nanoparticles was carried out by XRD, TEM, SEM, AFM, VSM and BET surface area analysis. TEM analysis confirmed the formation of nanoparticles in the range of approximate 12–21nm having the surface area of 41.31m2g−1. The saturation magnetization of nanoparticles was determined to be 50.8Am2kg−1. Langmuir adsorption capacity of CoFe2O4 nanoparticles was calculated to be 16.73mgg−1. Kinetic study revealed that the Cr(VI) removal on CoFe2O4 nanoparticles followed the pseudo-second-order kinetic model. Further, the temperature study revealed the endothermic nature of Cr(VI) adsorption. Thermodynamic study revealed the feasibility of Cr(VI) adsorption on CoFe2O4 nanoparticles. Desorption study suggested that nanoparticles could be efficiently reused up to three cycles. The present study demonstrated that synthesized nanoparticles were quite efficient for the treatment of chromium ions and other metallic ions from printing press wastewater which further suggested that CoFe2O4 nanoparticles could be successfully used for the treatment of metal- rich industrial effluents.

Insolubilization of hexavalent chromium in highly alkaline cement sludge by anaerobic bioremediation

ABSTRACTChemical treatment using reducing agents such as ferrous sulfate is the most popular method for remediation of hexavalent chromium–contaminated sludge. However, the use of such chemical agents poses the risk of secondary pollution through the elution of other heavy metals. Therefore, a bioremediation method was developed to remediate high-alkali cement sludge containing hexavalent chromium. When a biomediator mainly composed of lignocellulose and lignoarabinoxylan was added to hexavalent chromium–contaminated sludge under anaerobic conditions, the amount of hexavalent chromium eluted from the treated sludge decreased significantly to below the level of the environmental standard value in Japan and its pH was reduced to 8. Moreover, the oxidation-reduction potential of the treated sludge decreased and its microbiota changed. These results indicate that anaerobic microbes can facilitate the change of hexavalent chromium to an immobilized form of trivalent chromium. Nucleotide sequence analysis suggested that anaerobic microbes activated in the sludge were Exiguobacterium aurantiacum, which are known to tolerate high pH environments and produce organic acids, even in the cement sludge. Finally, treated sludge did not elute hexavalent chromium during shaking in acid or alkaline solution.

Stabilisation of nanoscale zero-valent iron with biochar for enhanced transport and in-situ remediation of hexavalent chromium in soil

In this study, a biochar-supported nanoscale zero-valent iron (nZVI@BC) material was used for in situ remediation of hexavalent chromium-contaminated soil. Sedimentation tests and column experiments were used to compare the stability and mobility of nZVI@BC and bare-nZVI. The immobilisation efficiency of chromium, toxic effect of chromium and the content of iron were assessed through leaching tests and pot experiments. Sedimentation tests and transport experiments indicated that nZVI@BC with nZVI to BC mass ratio of 1:1 exhibited better stability and mobility than that of bare-nZVI. The immobilisation efficiency of Cr(VI) and Crtotal was 100% and 92.9%, respectively, when the soil was treated with 8 g/kg of nZVI@BC for 15 days. Moreover, such remediation effectively reduced the leachability of Fe caused by bare-nZVI. In addition, pot experiments showed that such remediation reduced the phytotoxicity of Cr and the leachable Fe and was favourable for plant growth.

Microchannel-embedded metal–carbon–polymer nanocomposite as a novel support for chitosan for efficient removal of hexavalent chromium from water under dynamic conditions

A blend of micron-sized chitosan and carbon nanofibers (CNFs)-supported iron (Fe)-oxide nanoparticles (NPs) was dispersed in a modified polyvinyl alcohol to produce an approximately 1mm-thick metal–carbon–polymer nanocomposite film. The film was laser-ablated to create microchannels (150μm-wide, 100μm-deep and 30mm-long), thereby exposing the in situ dispersed chitosan and Fe-oxide NPs to the surrounding liquid through the porous walls of the fabricated microchannels. The prepared micro-textured nanocomposite film was used as a novel contactor for the remediation of hexavalent chromium (Cr(VI))-contaminated water under flow conditions. The material showed a high metal-uptake (∼80mgperg of chitosan/Fe-CNF composite), which was approximately the same as the equilibrium adsorption capacity determined under batch conditions. The spent nanocomposite film could be successfully regenerated and reused four times. The prepared material cum contactor in this study provides a potential solution to the difficulty of supporting all such micron- and submicron (nano)-sized metal/polymer particles that are prone to elution in liquid flow, by providing them a mechanically and thermally stable support for their practical use in separation and purification applications.

Adsorptive remediation of hexavalent chromium from synthetic wastewater by a natural and ZnCl2 activated Sterculia guttata shell

The present study deals with the removal of Cr(VI) ions from aqueous solutions by raw Sterculia guttata shell waste (RSGS) and ZnCl2 activated S. guttata shell waste (ASGS). Effect of various process parameters like solution pH, adsorbent dose, initial Cr(VI) concentration and temperature has been studied in batch system. The experimental data were fitted to the isotherm models. Langmuir isotherm model best fitted the adsorption equilibrium data and the adsorption capacity of RSGS and ASGS was found as 45.45 and 90.90mg/g respectively at 2.0pH. The data were analyzed on the basis of pseudo-first-order, pseudo-second-order, intra-particle diffusion and Boyd models. Higher degree of coefficient of determination was obtained for the pseudo-second-order kinetic model. The calculated thermodynamic parameters such as ΔG°, ΔH° and ΔS° showed that the adsorption of Cr(VI) ions onto adsorbents was spontaneous, endothermic and increased randomness in nature. Desorption study was carried out with different concentrations of NaOH solutions. The results of the present study suggested that RSGS and ASGS can be used beneficially in treating industrial effluents containing hexavalent chromium.

Environmental Remediation of Hexavalent Chromium in Aqueous Medium Using Fe(II)-Montmorillonite as Reductant

Hexavalent chromium contamination of groundwater and soil possess a significant threat to human health and the environment. The remediation by reduction, Cr(VI) → Cr(III), with a variety of reducing agents and techniques are explored for many years. In this study, Fe(II)–montmorillonite (Fe(II)–mont) was interacted with K2Cr2O7 solution at different pH and temperature. The decreasing Cr(VI) concentration was monitored by UV-Vis spectrophotometer. In general, the Cr(VI) reduction was rapid at acidic pH and increases with temperature up to 40 0C. There was 100% reduction achieved in pH 3 – 5 at 30 and 45min respectively. At different temperature time taken for 100% reduction at 0 0C, RT (30 0C) and 40 0C was 120, 60 and 30min respectively. The reduction followed by immobilization of Cr on the spent clay mineral was evident from FESEM/EDX and chemical extraction analysis. The results also revealed that the prepared Fe(II)–mont could be potentially applied as a adsorbent enabling promising applications for the removal of Cr(VI) from aqueous solution.

Using Ferrous Ion for the Reductive Degradation of Hexavalent Chromium

This paper discusses the toxicity and mobility of chromium species. And it presents the extent and kinetics of reductive remediation of hexavalent chromium, Cr+ using ferrous ion, Fe2+. Molar ratios of 1:3 and 1:6 of Cr (VI) to Fe (II) were used. Integral method of data analysis showed reaction followed second-order kinetics with R square values near unity. Reaction was initially fast but with a rapid precipitation attributed to Cr (III)-Fe (III) in previous studies. This colloidal precipitate ultimately stops the reaction, which explains while conversion efficiency increases with increased molar ratio of Cr (VI) to Fe (II). The impact of pH was investigated by adjusting the Cr (VI)-Fe (II) medium to pH 2.78, 5.24, 7.00, 9.00 and 11.96 using predetermined drops of acid or base. Reaction was more rapid under alkaline conditions with higher extent of degradation consistent with previous research. In soil system, mass transfer limitation was hardly noticed as high extent of reduction was recorded relative to aqueous phase. The high solubility of Cr (VI) aided the release into the aqueous media for reduction by ferrous sulfate.

Comment on “Enhanced Biosorptive Remediation of Hexavalent Chromium Using Chemotailored Biomass of a Novel Soil Isolate Bacillus aryabhattai ITBHU02: Process Variables Optimization through Artificial Neural Network Linked Genetic Algorithm”

ADVERTISEMENT RETURN TO ISSUEPREVCorrespondenceNEXTComment on “Enhanced Biosorptive Remediation of Hexavalent Chromium Using Chemotailored Biomass of a Novel Soil Isolate Bacillus aryabhattai ITBHU02: Process Variables Optimization through Artificial Neural Network Linked Genetic Algorithm”Xiang Cheng and Shaojun Li*View Author Information Key Laboratory of Advanced Control and Optimization for Chemical Process, Ministry of Education, East China University of Science and Technology, Shanghai 200237, People’s Republic of China*Tel.: +86-21-64253820. E-mail: [email protected]Cite this: Ind. Eng. Chem. Res. 2014, 53, 17, 7268–7270Publication Date (Web):April 15, 2014Publication History Published online15 April 2014Published inissue 30 April 2014https://doi.org/10.1021/ie501189cCopyright © 2014 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views353Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (156 KB) Get e-AlertsSUBJECTS:Chemical structure,Layers,Neural networks,Optimization,Theoretical and computational chemistry Get e-Alerts

Response to “Comment on ‘Enhanced Biosorptive Remediation of Hexavalent Chromium Using Chemotailored Biomass of a Novel Soil Isolate Bacillus aryabhattai ITBHU02: Process Variables Optimization through Artificial Neural Network Linked Genetic Algorithm’”

ADVERTISEMENT RETURN TO ISSUEPREVCorrespondenceResponse to “Comment on ‘Enhanced Biosorptive Remediation of Hexavalent Chromium Using Chemotailored Biomass of a Novel Soil Isolate Bacillus aryabhattai ITBHU02: Process Variables Optimization through Artificial Neural Network Linked Genetic Algorithm’”Devendra Kumar Verma†, Syed Hadi Hasan‡, Devendra Kumar Singh‡, Shalini Singh†, and Yogendra Singh*†View Author Information† †School of Biochemical Engineering and ‡Water Pollution Research Laboratory, Department of Applied Chemistry, Indian Institute of Technology (Banaras Hindu University), Varanasi−221005 (U.P.), India*Tel.: +91 9450283646. E-mail: yogendrasingh.rs.bce @iitbhu.ac.inCite this: Ind. Eng. Chem. Res. 2014, 53, 17, 7271–7272Publication Date (Web):April 15, 2014Publication History Published online15 April 2014Published inissue 30 April 2014https://doi.org/10.1021/ie501357uCopyright © 2014 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views295Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (142 KB) Get e-AlertsSUBJECTS:Bacteria,Biomass,Chromium,Neural networks,Soils Get e-Alerts

Remediation of hexavalent chromium contaminated soil by stabilized nanoscale zero-valent iron prepared from steel pickling waste liquor

Abstract The removal of Cr(VI) from contaminated soil using sodium carboxymethyl cellulose (CMC)-stabilized nanoscale zero-valent iron prepared from steel pickling waste liquor was systematically investigated. Laboratory batch experiments indicated that 0.09 g L −1 of Fe 0 nanoparticles at a soil to solution ratio of 1 g: 10 mL completely reduced the aqueous-bound Cr(VI), which contributed about 46% of the pre-sorbed Cr(VI) in the soil (Cr(VI) = 102 mg kg −1 ). Furthermore, the addition of Fe 0 nanoparticles only removed a portion of the soil-bound Cr(VI). When the soil was treated with 0.3 g L −1 of Fe 0 nanoparticles for 72 h, 80% of the loaded Cr(VI) was reduced to Cr(III), which resulted in a residual Cr(VI) concentration of 20 mg kg −1 . Based on the studies of elemental distributions and XPS analysis, it is proposed that reduction and immobilization may be equally important removal mechanisms for Cr(VI) by CMC-nZVI. Following the treatment by CMC-nZVI, the TCLP leachability of the Cr(VI) and Cr total was significantly reduced by 100% and 82%, respectively. This study sheds new light on the remediation of Cr(VI)-contaminated soil by CMC-nZVI.

Enhanced Biosorptive Remediation of Hexavalent Chromium Using Chemotailored Biomass of a Novel Soil Isolate Bacillus aryabhattai ITBHU02: Process Variables Optimization through Artificial Neural Network Linked Genetic Algorithm

A modified biomass of a novel bacterium, Bacillus aryabhattai ITBHU02, was investigated for the removal of hexavalent chromium [Cr(VI)] from water. It was found that modification of the biomass had an improved 28.2% higher Cr(VI) removal and 9.4 mg/g greater uptake capacity as compared to unmodified biomass. At ANN-GA optimized condition of parameters, namely, pH 2.61, biomass dose of 2.8 g/L, temperature of 44 °C, and initial Cr(VI) concentration of 112 mg/L, the maximum uptake capacity of biomass was achieved as 31.2 mg/g and removal was 93.6%. The residual 6.4% chromium in water was found in the form of Cr(III) instead of Cr(VI), which clearly illustrated the reduction of toxic Cr(VI) into nontoxic Cr(III) due to the detoxification capability of biomass during the sorption process. Sorption followed pseudo-second order kinetics with a monolayer pattern in an endothermic and spontaneous way. SEM-EDX and FTIR studies were used to confirm the sorption as well as the functional groups involved in the sorption process.

ChemInform Abstract: Chemical and Microbial Remediation of Hexavalent Chromium from Contaminated Soil and Mining/Metallurgical Solid Waste: A Review

AbstractReview: 231 refs.

Effect of Alternative Electrolytes on Enhanced Electrokinetic Remediation of Hexavalent Chromium in Clayey Soil

Hexavalent chromium is mobile and hazardous in the environment. Electrokinetic remediationof chromium (IV)-contaminated soils is intended either to remove or to reduce Cr (VI) to Cr (III). This studyexamines the effectiveness of utilizing EDTA and acetic acid solutions as alternative electrolytes in theelectrokinetic (EK) process, with coupled nano-scale zero-valent iron (nZVI) as a barrier for the remediationof Cr (VI)-contaminated clay. An nZVI barrier was installed adjacent to the anode, and different electrolytesolutions (0.1 M EDTA and 1 M acetic acid) were used to investigate the effect of both on the electrokineticremediation efficiency. Soil was contaminated to 300 ppm of Cr (IV), and a constant DC voltage gradient of1 V/cm was applied to the soil sample for 72 h. It was found that an nZVI permeable reactive barrier (PRB)could improve the Cr (VI) remediation efficiency and reduce electrical energy consumption. Results alsoshowed that acetic acid as electrolyte promoted the reduction of Cr (VI) to Cr (III), while EDTA applicationas electrolyte led to more chromium removal and reduction than an EK-nZVI barrier.

Remediation of hexavalent chromium by consortia of indigenous bacteria from tannery waste-contaminated biotopes in Fez, Morocco

Bioremediation is a promising, safe and economical technology widely used to clean up both soils and wastewaters containing Cr(VI). Most work uses pure microbial cultures. Little research has been done with mixed microbial cultures. In this study, consortia of indigenous bacteria isolated from a polluted site have been used to study the effect of different conditions such as Cr(VI) concentration, metal ions, electron donors and pH on Cr(VI) reduction by the consortia. We also evaluate the microbial ability to detoxify repeatedly and continuously in a non-modified medium. Results show that consortia of indigenous bacteria are resistant to greater than 200 mg/L Cr(VI). However, mixed cultures exhibited decreasing diversity with increasing levels of chromate. The consortia show high Cr(VI) removal capacity under various conditions and exhibit an ability for continuous reduction of Cr(VI) up to three consecutive inputs. The consortia may be appropriate for environmental applications for Cr(VI) remediation.

Stabilization of Fe 0 nanoparticles with silica fume for enhanced transport and remediation of hexavalent chromium in water and soil

Effective in situ remediation of Cr(VI) in groundwater requires the successful delivery of reactive iron particles to the subsurface. Fe 0 nanoparticles (20–110 nm diameter) supported on silica fume were synthesized by borohydride reduction of an aqueous iron salt in the presence of a support material. The experimental result showed that attachment of Fe 0 nanoparticles on the commercial available sub-micrometer silica fume prevented them from aggregation while maintaining the particle reactivity. When the Fe 0 concentration was 0.4 g/L, 88.00% of 40 mg/L Cr(VI) was removed by silica fume-supported Fe 0 nanoparticles (SF-Fe 0) in 120 min, 22.55% higher than unsupported Fe 0. Furthermore, transport experiments confirmed that almost all unsupported Fe 0 was retained, whereas 51.50% and 38.29% of SF-Fe 0 were eluted from the vertical and horizontal sand column, respectively. Additionally, the effect of solution ionic strength on the transport ability of SF-Fe 0 was evaluated. The result showed that increase in the salt concentration led to a decrease in the mobility and also the divalent ion Ca 2+ had a greater effect than that of monovalent ion Na +.