乙醇对过硫酸盐去除石灰岩含水介质中汽油组分BTEX的影响

随着乙醇汽油的推广应用,其污染岩溶地下水的环境问题受到越来越多的关注。汽油组分苯、甲苯、乙苯和二甲苯(BTEX)可以被过硫酸盐(PS)化学氧化作用有效去除。然而,乙醇的存在是否影响PS去除BTEX尚缺乏深入研究。利用石灰岩颗粒为介质,以汽油组分BTEX(总浓度为20 mg/L)和乙醇(浓度分别为500,5000 mg/L)为污染物,通过微元体(Microcosm)实验模拟污染的岩溶地下水环境,研究PS分别去除BTEX和乙醇,以及同时去除BTEX和乙醇的效果,讨论了乙醇对PS去除BTEX的影响。结果表明:前28 d,PS可以去除91%的BTEX,准一级动力学常数为0.006~0.349 d-1,其中苯最难去除,其次为甲苯。乙醇能够被PS有效去除,准一级动力学常数为0.003~0.054 d-1,去除速率小于BTEX;乙醇与BTEX共存时能够抑制BTEX的去除,但不会影响BTEX去除的优先性。PS浓度增大,有利于去除乙醇和BTEX,但会抑制微生物活性,促使pH值下降,并导致CaSO₄沉淀。该试验结果可为乙醇汽油污染岩溶地下水的原位化学氧化研究提供科学参考。

EFFECTS OF ETHANOL ON REMOVAL OF BTEX FROM GASOLINE BY PERSULFATE IN LIMESTONE AQUEOUS MEDIA

With the increasing application of ethanol gasoline, the contaminated karst groundwater by its release has been concerned. Benzene, toluene, ethylbenzene, and xylene (referred to as BTEX) in gasoline can be effectively removed by in situ chemical oxidation using persulfate (PS). However, it’s still not clear whether the presence of ethanol affects the removal of BTEX by PS. In this paper, limestone particles, acting as the aqueous media, and gasoline BTEX (20 mg/L) combined with ethanol (500 mg/L or 5000 mg/L), acting as the pollutants, were used to form microcosms and simulate a contaminated karst groundwater environment. BTEX and ethanol removal effects by PS chemical oxidation were studied respectively, as well as their removal effects in coexistence. The results showed that 91% of BTEX was removed by PS in the first 28 days, with the first-order rate constants ranging from 0.006 to 0.349 d-1. Benzene was the most difficult to remove, followed by toluene. Ethanol was removed by PS with the pseudo-first-order rate constants ranging from 0.003 to 0.054 d-1, which was less than that of BTEX. The presence of ethanol could decrease the removal rate of BTEX, but couldn’t affect the removal priority of BTEX. The increase of PS concentration was beneficial to the removal of ethanol and BTEX, nevertheless, which could inhibit microbial activity, make the pH value drop more, and cause calcium sulfate precipitation. This work provides scientific data for in situ chemical oxidation of karst groundwater contaminated by ethanol gasoline.