Detailed study on reduction of hazardous Cr(VI) at acidic pH using modified montmorillonite Fe(II)-Mt under ambient conditions
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Contamination of groundwater and soil by high levels of hexavalent chromium directly affects the environment and human health as a serious pollutant. Remediation by reduction, i.e., Cr(VI) → Cr(III), using a variety of reducing agents and/or processes has been explored for many years. In the present study, application of Fe(II)-Montmorillonite [a dioctahedral smectite, Fe(II)-Mt] containing interlayer Fe(II) ions as an environmentally benign clay mineral for reduction of Cr(VI) in acidic pH from aqueous solution was investigated. Fe(II)-Mt was reacted at stoichiometric excess [Fe(II)-Mt: 0.32 g; Cr(VI): 1 mM, 100 mL] in K2Cr2O7 solution at pH of 5.5 and 3.0. The decrease of Cr(VI) was monitored spectrophotometrically, and the results were corrected for the anion exclusion effect, i.e., the electrostatic interaction of HCrO 4 − ions with the negatively charged surface of the clay mineral. Stoichiometric reduction of Cr(VI) was achieved in short time; at pH 5.5, 20 % reduction was achieved in the first 10 min, after which the reduction proceeded gradually to consume all of the interlayer Fe(II) ions at about 6 h. On the other hand, at pH 3.0, the reaction completed in about 15 min. Moreover, Fe(II)-Mt clay mineral can be conveniently prepared and handled in large amounts, making this method feasible even for remediation of Cr(VI) contamination over large areas in real applications.
KeywordsCr(VI) contamination Environmental remediation Cr(VI) reduction Fe(II)–montmorillonite [Fe(II)-Mt]
M.V. acknowledges the Principal, and Board of Management NIE-IT for encouragement and support throughout this research work. The authors thank Mr. K. Chandrasekhar for help with XRD analysis, and Prof. G. U. Kulkarni at JNCASR for providing FESEM facility.
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