• 关键词：硝酸盐  土壤水  Fe⁰  黄土地区

• 基金项目：陕西省自然科学基金(No.2005C105)

• 唐次来
• 西北农林科技大学理学院, 杨凌 712100

• 朱艳芳
• 西北农林科技大学生命科学学院, 杨凌 712100

• 张增强
• 西北农林科技大学理学院, 杨凌 712100

• 张英超
• 西北农林科技大学理学院, 杨凌 712100

• 摘要：在欧美发达国家,以Fe⁰为填料的PRB(permeable reactivebarriers)技术已成功用于去除土壤和地下水中的硝酸盐污染,而在我国的实际应用还未见报道,但我国许多地区的土壤水中硝酸盐污染日趋严重,必须采取相应措施.为此,在实验室条件下,通过批实验采用200～300目的还原铁粉研究了在有黄土存在时溶液pH、铁粉表面预处理及铁粉与硝态氮质量比、土壤水中主要阴离子及加活性炭等对硝酸盐去除效果的影响.结果表明,在黄土的碱性条件下,Fe⁰仍然可以还原硝酸盐,起始pH值影响不大,因为土壤的缓冲作用能抵消进水pH值的影响;铁粉经过酸预处理后能提高反应速率和硝酸盐的去除率;增大铁粉与硝态氮的质量比能提高硝酸盐的去除率,但当这个比值超过100∶1以后,用酸预处理和不作预处理的效果相当,且再增大比值对硝酸盐的去除率影响不大.黄土地区土壤水中的主要阴离子Cl^-、SO₄^2-和HCO₃^-可促进铁粉腐蚀进而加快硝酸盐的还原,同浓度下促进作用顺序为SO₄^2-(HCO₃^-(Cl^-;加入活性炭可形成原电池从而加快硝酸盐的去除.硝酸盐还原产物主要是氨,亚硝酸盐只是在反应初期出现但很快就减少,可溶性铁含量都小于0.2mg·L^-1.

• Abstract：Permeable reactive barriers (PRB) based on zero-valent iron have been implemented successfully for nitrate removal from groundwater in developed countries, but they have not been used for field-scale applications in China even though groundwater nitrate pollution is very serious in most areas of China. Batch experiments were conducted using 200～300 mesh reducing iron powder to test the effects of parameters including: initial pHof the water; pretreatment of the iron with dilute acid; the weight ratio of iron to nitrate-N; addition of active carbon; and the concentration of the major anions present in the water. The results indicated that zero-valent iron could reduce the nitrate under the alkaline conditions of loess soils. The effect of the original pHvalue was not great because the buffer effect of the soil counteracted the effect of the influent water's pH. The nitrate removal rate was increased when the iron was pretreated with dilute acid or if the ratio of iron to nitrate-N was higher. However, the advantage of pretreating the iron was eliminated if the weight ratio of iron to nitrate-Nwas above 100 and the removal rate of nitrate remained constant even if the ratio was higher, because the proportion of nitrate removed reached 100%. Nitrate reduction was enhanced by the major anions in loess soils such as Cl^-, SO₄^2- and HCO₃^-, which contribute to iron corrosion. At the same concentrations, the promotion effect decreased in the order: SO₄^2-﹥HCO₃^-﹥Cl^-. The nitrate removal rate could also be enhanced by adding active carbon. The primary product of nitrate reduction was ammonia. Nitrite was only present at the beginning of the reaction and decreased rapidly. The concentration of dissoluble Fe(Ⅱ) and Fe(Ⅲ) in the solution was less 0.2 mg·L^-1.

• Key words：nitrate  soil water  zero-valent iron  loess soils

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