摘要
在欧美发达国家,以Fe0为填料的PRB(permeable reactive barriers)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-、SO42-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SO42-(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.
Permeable reactive barriers （PRB） based on zcro-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 pH of the water; pretreatment of the iron with dilute acid ; the weight ratio of iron to nitrate-N ; addition of aetive 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 pH value was not great beeanse 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-N was above 100 and the removal rate of nitrate remained constant even if the ratio was higher, beeanse 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 raoidlv. The concentration of dissoluble Fe（ Ⅱ ） and Fe（ Ⅲ ） in the solution was less 0.2 mg·L^-1
出处
《环境科学学报》
CAS
CSCD
北大核心
2007年第8期1292-1299,共8页
Acta Scientiae Circumstantiae
基金
陕西省自然科学基金(No.2005C105)~~
关键词
硝酸盐
土壤水
Fe0
黄土地区
nitrate
soil water
zero-valent iron
loess soils
作者简介
唐次来（1981-）男,硕士,E-mail：bolong8111@163.com
张增强（1963-）,通讯作者（责任作者）,男,教授,博士生导师.主要从事固体废弃物资源化研究.E-mail：zhangzq58@126.com.
