电压对氧化剂和活化剂在土壤中的迁移及对PAHs去除的影响

Effects of voltage on the migration of oxidant and activator and the removal of PAHs in soil during electrokinetic-enhanced in situ chemical oxidation

为探究电动-原位化学氧化(EK-ISCO)中不同电压对土壤中氧化剂、活化剂迁移和污染物去除的影响,以多环芳烃(PAHs)污染土壤为研究对象,通过电动土柱试验(阳极投加氧化剂过硫酸钠,阴极投加活化剂柠檬酸亚铁),研究了4种电压(5、10、20 V和40~30 V)对土壤中氧化剂、活化剂的迁移机制及对污染物去除的影响。结果表明:电流随着电压的升高而升高,最高电流出现在40~30 V电压处理;电渗量与电压关系较为复杂,10 V电压处理获得了最高的电渗流(981 mL),其次是40~30 V和20 V处理,5 V处理电渗流最低;10 V电压处理的高电渗流有利于过硫酸盐从阳极向土柱中迁移,而较高的电压(20 V和40~30 V)一方面减弱了电渗流,减少了过硫酸盐向土柱中迁移,另一方面高电流加快了阴极液和阴极附近土壤溶液的碱化,降低了柠檬酸亚铁的活性,不利于柠檬酸亚铁从阴极向土柱迁移并与过硫酸盐反应。从PAHs去除率来看,10 V处理总去除率可达37.0%,高于其他处理的21.3%~28.4%,且能耗相对较低(268.6 kWh·t^(-1))。研究表明,10 V电压处理有利于氧化剂和活化剂在土柱中的迁移和反应,可获得最高的PAHs去除率和相对较低的电能消耗,是适宜的电压条件。

To investigate the effects of voltage on the migration of oxidant and activator and the removal of pollutants in soil during electrokinetic-in situ chemical oxidation(EK-ISCO),four voltages(5,10,20 V,and 40-30 V)were used to explore the removal of polycyclic aromatic hydrocarbons(PAHs)in soil via electrokinetic column experiments(adding sodium persulfate as an oxidant at the anode and ferrous citrate as an activator at the cathode).The results showed that the current increased with an increase in voltage,and the highest current occurred in the 40-30 V treatment.However,the relationship between electroosmotic flow(EOF)and voltage was complex.The 10 V treatment had the highest EOF(981 mL),followed by the 40-30 V and 20 V treatments,and the 5 V treatment had the lowest EOF.The 10 V treatment was beneficial to the migration of persulfate from the anode to the soil column,whereas higher voltages(20 V and 40-30 V)weakened the EOF,accelerated the alkalization of the catholyte and soil solution near the cathode,reduced the activity of ferrous citrate and was unfavorable for the migration of persulfate and ferrous citrate from the anode and cathode to the soil column.In terms of the PAH removal rate,in the 10 V treatment,the total removal rate reached 37.0%,which was higher than 21.3%-28.4%of the other treatments,and the energy consumption was relatively low(268.6 kWh·t^(−1)).In conclusion,the experiments showed that a 10 V treatment was favorable for the migration and reaction of oxidant and activator in the soil column and had the highest PAH removal rate and relatively low energy consumption,which indicated that 10 V was the appropriate voltage condition.