Adsorption of Cr(Ⅵ) by nano iron oxide and the surface?catalyzed Cr(Ⅵ) reduction by citric acid were examined together with their significance in soil environments. As the results showed, nano iron oxide had high capacity for Cr(Ⅵ) adsorption, which was unfavorable when pH and ionic strength were increased. The Cr(Ⅵ) adsorption was characterized by an initial fast phase followed by a slow phase, evidenced by the adsorbed Cr(Ⅵ) accounting for 80%of the total amount within 5 min. Cr(Ⅵ) reduction by citric acid was accelerated in the presence of nano iron oxide, especially at low pH. Fe (Ⅱ) generated from the interaction between citric acid and aqueous Fe(Ⅲ) partly contributed to the catalytic effect. Moreover, Cr(Ⅵ) reduction in the oxisol?citric acid system was relatively low, and was promoted with the addition of nano iron oxide. The result suggest that nano iron oxides in soil environments are helpful to alleviate the risk posed by Cr(Ⅵ) .
nano iron oxidecitric acidhexavalent chromiumsoil environments
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