pH;
zerovalent iron;
nitrate;
iron oxides;
kinetics;
D O I:
10.1016/j.watres.2004.03.015
中图分类号:
X [环境科学、安全科学];
学科分类号:
08 ;
0830 ;
摘要:
The effect of low pH (2-4.5) on nitrate reduction in an iron/nitrate/water system was investigated through batch experiments conducted in a pH-stat. The results showed that nitrate could be rapidly reduced to ammonium at pH 24.5. A black coating, consisted of both Fe(II) and Fe(III), was formed on the surface of iron grains as an iron corrosion product. X-ray diffractometry indicated that the black coating was poorly crystalline, and its spectrum could not be matched with commonly known iron oxides/hydroxides/oxide hydroxides or green rust I/II. The black coating does not inhibit the reactivity of Fe-0 (at least at pH < 3). The black coating was unstable and evolved with time into other oxides under certain conditions. A kinetic model incorporating the effects of pH on nitrate reduction and Langrymuir adsorption of nitrate was proposed, and the parameters were estimated by nonlinear curve fitting. Based on this model, the two major effects of pH on the kinetics of nitrate reduction are that: (a) H+ ions directly participate in the redox reaction of nitrate reduction following first-order kinetics; and (b) H+ ions affect the nitrate adsorption onto reactive sites. (C) 2004 Elsevier Ltd. All rights reserved.