碱活化过硫酸钠和热脱附技术对TPH和PAHs污染土壤修复的试验研究

Experimental Study on Remediation of TPH and PAHs Contaminated Soil by Alkali-activated Sodium Persulfate and Thermal Desorption

该研究以上海市某地块石油烃(TPH)和多环芳烃(PAHs)有机污染土壤为例,采用目前修复工程中常用的碱活化过硫酸钠和热脱附技术,分别对TPH和PAHs污染土壤开展修复模拟试验,根据污染去除效果确定了该氧化剂对不同浓度污染土壤的投加量和热脱附温度。在碱活化过硫酸钠体系中,针对低浓度的TPH和PAHs有机污染土壤修复时,投加1.0%的氧化药剂即可达到修复目标;对于高浓度的TPH和PAHs有机污染土壤修复时,投加3.0%的氧化药剂无法达到修复目标。随着药剂投加量的增加,目标污染物的去除率增幅减弱,大量地使用化学药剂修复经济性差且效果有限。采用热脱附技术,在脱附温度为300℃且持续加热1 h的条件下,即可将低浓度TPH和PAHs修复至达到目标值;而对于高浓度污染土,需将温度提升至500℃才可达到修复目标。脱附温度越高,目标污染物的去除效果越好,且其去除效果不受污染物浓度高低的限制。对于受污染土壤的治理应综合考虑经济、时间以及二次污染等因素来确定其适用的修复技术。

By taking soil contaminated by total petroleum hydrocarbon(TPH)and polycyclic aromatic hydrocarbon(PAHs)from a site in Shanghai as an example,experiments of remediation of TPH and PAHs contaminated soil were carried out in this paper using alkali-activation sodium persulfate and thermal desorption technology which commonly used in the remediation projects.The dosage of such oxidizing agent and the temperature of thermal desorption against the soils contaminated at different levels was determined according to the contamination removal effect.Soil contaminated by the low-concentration TPH and PAHs could be repaired by adding 1.0%oxidizing agent in the alkali-activation sodium persulfate system.However,TPH and PAHs of high concentration could not reach the remediation targets by adding 3.0%oxidizing agent.The growth of removal rate of target contaminant declined along with the increase of dosage.The remediation using a great quantity of chemical agent brought poor economic benefit and limited effect.With adoption of thermal desorption technology,the low-level TPH and PAHs could be repaired to target value after continuous heating for 1h at a desorption temperature of 300℃.For soil with high levels of contamination,the temperature should be raised to 500℃to achieve the target.The higher the desorption temperature,the better the removal effect of targeted contaminant.Furthermore,the removal effect was not limited by the levels of contaminant.As to the governance of contaminated soil,the appropriate restoration technique should be determined based on factors such as economy,time and secondary contamination.