2种水稻土胶体界面五氯酚的还原脱氯转化

研究了紫泥田和浅脚紫泥田2种水稻土胶体界面五氯酚(PCP)的还原转化效果,以及添加Fe2+或草酸对五氯酚还原转化效果的影响.采用表观一级反应动力学描述土壤胶体界面五氯酚的转化过程.结果表明,紫泥田和浅脚紫泥田土壤胶体界面五氯酚的还原转化动力学常数分别为0.0375d-1和0.0430d-1,半衰期分别为18.5d和16.1d;厌氧条件下水稻土胶体中铁氧化物还原溶解产生的吸附态Fe2+对五氯酚具有一定的还原转化能力.添加1.0mmol·L-1Fe2+或1.0mmol·L-1草酸均能显著促进土壤胶体界面五氯酚的还原转化和氯离子的产生,紫泥田土壤胶体界面五氯酚的还原转化半衰期分别减少到9.6d和6.0d,浅脚紫泥田土壤胶体界面五氯酚的转化半衰期分别减少到7.9d和3.0d.草酸促进作用更加显著的原因是铁-草酸配合物的生成.土壤胶体界面五氯酚的还原转化、脱氯效率与土壤胶体的比表面积、吸附态亚铁离子浓度有一定的正相关关系.促进土壤中吸附态亚铁离子和草酸等低分子量有机酸的产生能显著促进有机氯的还原转化.

Reductive Transformation of Pentachlorophenol in the Interface of Paddy Soil Colloids and Water

A series of batch experiments were carried out to investigate the reductive transformation of pentachlorophenol (PCP)in the interface of soil colloids from purple paddy soil(PPS)and flat purple paddy soil(FPPS)and water. The effect of additional 1.0mmol·L-1 Fe2+ and oxalate on the reductive transformation of PCP and the generation of chlorine were also investigated. Reductive transformation could be well described by first-order kinetics model. Results showed that PCP could be reductively transformed and dechlorinated in the interface of both soil colloids and water. The kinetics rate constants of PCP transformation were 0.0375, 0.0430d-1, respectively, and half-life time were 18.5, 16.1d for PPS and FPPF, respectively. Obviously, the additional 1.0mmol·L-1 Fe2+ or oxalate could significantly enhance the reductive transformation of PCP and the generation of chlorine. The half-life time for PCP transformation decreased significantly to be 9.6 and 6.0d in the PPF-water interface, while that decreased to be 7.9 and 3.0d in the FPPS-water interface owing to additional Fe2+ and oxalate, respectively. The enhanced effect of additional Fe2+ and oxalate should be attributable to the formation of adsorbed Fe2+ with a higher concentration. It is very interesting that the enhanced effect of oxalate should be more significant than that of Fe2+ because the generated Fe-oxalate complex have a lower reductive potential than Fe2+. This investigation will give some new insights in soil remediation on site.