Influence of various organic molecules on the reduction of hexavalent chromium mediated by zero-valent iron

• Published in: Chemosphere (Oxford) Vol. 76; no. 9; pp. 1240 - 1248
• Main Authors: Rivero-Huguet, Mario, Marshall, William D.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.08.2009; Elsevier
• Subjects: Acids - chemistry; Air. Soil. Water. Waste. Feeding; Animal, plant and microbial ecology; Applied ecology; Applied sciences; Ascorbic acid; Biological and medical sciences; Carboxylates; Chelating; Chelating Agents - chemistry; Chromium - chemistry; Ecotoxicology, biological effects of pollution; Environment. Living conditions; Environmental Restoration and Remediation; Ethylenediaminetetraacetic acids; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Hexavalent chromium; Hydrogen-Ion Concentration; Iron - chemistry; Medical sciences; Organic Chemicals - chemistry; Organic molecules; Oxidation-Reduction; Pollution; Public health. Hygiene; Public health. Hygiene-occupational medicine; Reduction; Reductive remediation; Soil Pollutants - chemistry; Soils; Water Pollutants, Chemical - chemistry; Zero-valent iron; Hexavalent chromium; Reductive remediation; Organic molecules; Zero-valent iron; Hexavalent metal; Decontamination; Zerovalent metal; Iron
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2009.05.040

Hexavalent chromium is a priority pollutant in many countries. Reduction of Cr(VI) to Cr(III) is desirable as the latter specie is an essential nutrient for maintaining normal physiological function and also has a low mobility and bioavailability. A variety of naturally-occurring organic molecules (containing α-hydroxyl carbonyl, α-hydroxyl carboxylate, α-carbonyl carboxylate, phenolate, carboxylates and/or thiol groups, siderophore, ascorbic acid); chelating agents (ethylenediaminetetraacetic acid derivates, acetyacetone) and others were examined their reducing activity towards a surfactant preparation (Tween 20) containing Cr(VI) and Fe(0) under a variety of reaction conditions. An appreciable enhancement (up to 50-fold) of the pseudo-first-order rate constant was achieved at acidic and circum neutral pH values for those compounds capable of reducing Cr(VI) (α-hydroxyl carboxylate, ascorbic acid, cysteine). Comparable enhancements were obtained for certain chelating agents (ethylenediaminetetraacetic acid derivates and siderophores) which is attributed to the formation of complexes with reaction products, such as Cr(III) and Fe(III), which impede the precipitation of Cr(III) and Fe(III) hydroxides and Cr x Fe 1− x (OH) 3 and thus reduce passivation of the Fe(0) surface. The results suggest that these molecules might be used in effective remediation mediated by Fe(0) of Cr(VI)-contaminated soils or groundwater in a wide range of pH, thus increasing reaction rates and long-term performance of permeable reductive barriers.