• 关键词：零价铁  硝酸盐  阴离子  动力学

• 基金项目：陕西省自然科学基金(No.2005C105)

• 唐次来
• 西北农林科技大学　资源与环境学院, 杨凌 712100

• 张增强
• 西北农林科技大学　理学院, 杨凌 712100

• 李荣华
• 西北农林科技大学　理学院, 杨凌 712100

• 摘要：通过批实验,考察了4种无机阴离子(HCO₃^-、SO₄^2-、Cl^-和PO₄^3-)和3种有机阴离子(C₂O₄^2-、C₆H₅O₇^3-和CH₃COO^-)对Fe⁰还原NO₃^-的影响.结果表明,除PO₄^3-外,其它离子都能不同程度地促进NO₃^-的还原,促进程度与其浓度有关.由于PO₄^3-与铁及其腐蚀物具有强吸附作用,占据了活性点位,从而明显抑制了NO₃^-的还原;而其它无机离子由于与Fe(Ⅱ)/Fe(Ⅲ)的络合作用而促进铁的腐蚀,同时它们与铁氢氧化物形成的绿锈也有助于NO₃^-的还原.有机离子主要因为络合作用促进了铁腐蚀而加快NO₃^-的还原,也存在部分有机离子由于在铁表面的吸附作用占据活性点位而不利于硝酸盐还原的情况,但前者作用更强.在所有体系中,NO₃^-还原的主要产物是氨,NO₂^--N只在前期有少量积累,随后降低到1.0mg·mL^-1以下.由于加入离子的络合作用,增加了可溶性铁的含量,尤其是添加有机阴离子的处理中可溶性铁最高时达246.2mg·mL^-1.反应后的溶液中检测到的三氮(NO₃^--N、NO₂^--N和NH₄⁺-N)之和只有理论总氮的50%～80%.在所有体系中,NO₃^-还原基本符合一级反应动力学.本研究结果有助于了解水和废水中常见阴离子对Fe⁰还原NO₃^-的影响大小和作用机理,为实际应用提供理论参考.

• Abstract：Batch tests were conducted to investigate the effects of four inorganic anions(bicarbonate、sulfate、chloride and phosphate)and three organic anions(oxalate、citrate and acetate)on nitrate reduction by zero-valent iron(Fe⁰).The results demonstrated that all anions except phosphate enhanced nitrate reduction to some degree depending on their concentrations.Phosphate significantly inhibited nitrate reduction because of its strong adsorption on the surface of Fe⁰ and its corrosion products,such that phosphate occupied the nitrate reduction reaction sites.But other inorganic anions promoted the corrosion of iron through complexation with Fe(Ⅱ)/Fe(Ⅲ).Moreover,these inorganic anions transformed to green rusts by combining with Fe(Ⅱ)-Fe(Ⅲ)oxyhydroxides,which were able to reduce nitrate to ammonia.Organic anions accelerated the corrosion of iron because they form complexes with iron corrosion products.Synchronously,their adsorption on the surface of Fe⁰ occupied some of the active sites which are related to nitrate reduction.However,the acceleration by organic anions was stronger than the inhibition of nitrate reduction.Ammonia was the dominant end-product for nitrate reduction by Fe⁰,but nitrite accumulated only a little in the prior period and finally decreased to below 1.0 mg·L^-1.The complexation of added anions with Fe(Ⅱ)/Fe(Ⅲ)led to the accumulation of dissolved iron in solution,especially after organic anions were introduced.Finally,in the all treatments adding Fe⁰,the sum of three nitrogen(NO₃^--N、NO₂^--Nand NH₄⁺-N)in the solution were just about 50%～80% of the theoretical total net nitrogen.Kinetics analysis revealed that the denitrification reaction by Fe⁰ appeared to occur by a pseudo-first-order model.This research may lead to an understanding of the mechanisms and effects of normal anions in water on nitrate reduction by Fe⁰,and it may provide guidance for practical application in the remediation of ground water pollution.

• Key words：zero-valent iron  nitrate  anions  kinetics

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