预加入柠檬酸螯合亚铁对过硫酸盐降解土壤中农药的影响

螯合亚铁活化过硫酸盐可高效氧化降解土壤中有机污染物，但由于土壤组分的竞争效应，通常情况下修复药剂的利用效率较低. 本研究选取柠檬酸螯合亚铁(Fe2+-CA)为模型活化剂，考察了活化剂预加入对其活化过硫酸盐(PS)氧化降解不同土壤中农药、多环芳烃的影响. 结果表明:Fe2+-CA的预加入影响了柠檬酸螯合亚铁活化过硫酸盐体系(简称“Fe2+-CA/PS体系”)对土壤中莠去津的降解效果，土壤中莠去津的降解率与活化剂预加入时间的关系呈倒U型趋势线，其中在活化剂预加入约5 min时，莠去津的去除率(73.6%)达最大值，相比修复药剂直接加入体系的效果增加了17%. 相关测试表征显示，在活化剂预加入5 min的情况下硫酸根自由基的贡献增大，降低了土壤有机质对氧化剂的消耗，提高了过硫酸钠的有效利用率，促进了土壤中污染物的降解. 柠檬酸螯合亚铁预加入约5 min时促进Fe2+-CA/PS体系降解土壤中污染物的效应适用于不同过硫酸钠常用浓度、不同类型土壤和不同有机污染物(包括农药和多环芳烃)，但促进效果通常与过硫酸盐用量、土壤类型、污染物种类有关. 莠去津污染土壤修复扩大规模试验证实，活化剂预加入5 min使Fe2+-CA/PS体系对含水率为饱和持水量80%的土壤中莠去津的降解效果提高了47%. 研究显示，Fe2+-CA预加入约5 min时对Fe2+-CA/PS体系降解土壤中有机污染物的促进效果最好. 

Effects of Pre-Addition of Citric Acid-Fe2+ Activator on Degradation of Pesticides in Soils by Fe2+-Citric Acid/Persulfates

Chelated ferrous iron is representative of highly efficient activators of persulfates for the removal of organic contaminants in soils. However, chelated ferrous iron-activated persulfate systems suffer from the low utilization efficiency of the remediation reagents, due to the well-known competition of natural soil components for the reactive substances. In this study, we chose citric acid-chelated ferrous iron (Fe2+-CA) as a model activator of persulfates, and investigated effects of pre-addition of Fe2+-CA on remediation performance and utilization efficiency of Fe2+-CA/PS for the removal of organic pollutants in soils. The results showed that pre-addition of Fe2+-CA by 0-120 min affected the degradation rates of atrazine in soils to different degrees, characterized by an inverse U type curve of activator addition interval (min). The maximal removal rate of atrazine by Fe2+-CA/PS was achieved when the activator was added about 5 min in advance. The removal rate of atrazine was 73.6% when the activator was added 5 min in advance. This removal rate was about 17% higher than when Fe2+-CA and PS were added simultaneously. In the soils treated by Fe2+-CA/PS, the contribution of sulfate radical increased significantly and the loss of soil organic matter and persulfates decreased when the activator was added 5 min in advance. These effects resulted in both improvement of atrazine removal and utilization efficiency of persulfates. This phenomenon was obtained in various Fe2+-CA/PS systems, despite large differences in oxidant doses, soil types, and types of organic contaminants. Scale up experiment of soil remediation demonstrated that the removal rate of atrazine in soils (approximately 80% of the maximal water holding capacity of soil) increased by 47% when Fe2+-CA/PS with activator was added 5 min in advance. The study showed that the Fe2+-CA/PS system had the best promotion effect on the degradation of organic pollutions in soil when Fe2+-CA was pre-added for about 5 min.