苯酚作用下有机改性膨润土化学相容性试验研究

Experimental study on impact of phenol solution on chemical compatibility of organically modified bentonites

季铵盐阳离子改性膨润土阻控有机污染物能力强,对水和无机盐溶液防渗性能不足。膨润土经亲水性有机聚合物改性,在无机盐溶液作用下渗透系数显著降低。为提升膨润土系竖向阻隔屏障对含有机物地下水污染羽的防渗性能,综合这两类膨润土有机改性的优势,采用季铵盐阳离子与亲水性有机聚合物共同改性膨润土。通过膨胀指数和改进滤失试验,对比十六烷基三甲基溴化铵和羧甲基纤维素钠(CTMAB-CMC)共同改性膨润土、CMC改性膨润土和未改性膨润土的化学相容性。试验结果表明,相同条件下CMC改性膨润土膨胀和防渗性能相对最优,而CTMAB-CMC改性则有效削弱苯酚溶液对膨胀指数和渗透系数的影响程度。综合特征官能团和黏土矿物(001)面特征衍射峰分析,CTMAB阳离子对苯酚的分配作用是改性膨润土化学相容性增强的主因。透射电子显微镜观测显示,苯酚溶液未显著影响改变两种改性膨润土的微观结构,CTMAB-CMC改性膨润土分散程度优于CMC改性膨润土。

Bentonite modified with quaternary ammonium cations possesses a high capacity of containing organic contaminants,meanwhile,its water or salt solution permeability could not meet the requirement of regulatory limitation.Polymer modification contributes to reducing hydraulic conductivity when bentonite is permeated with an inorganic salt solution.To enhance the performance of soil-bentonite cutoff wall for groundwater plumes containing organic contaminants containment,the advantages of both bentonite modification methods are overall considered;and,bentonite is modified using hexadecyl trimethyl ammonium bromide(CTMAB)and carboxymethylcellulose sodium(CMC).A series of swell index tests and modified fluid loss tests were conducted to compare the chemical compatibility of CTMAB-CMC-modified bentonite,CMC-modified bentonite,and unmodified bentonite.The results indicate that CMC-modified bentonite possesses a relatively highest swell index and lowest hydraulic conductivity value among the three groups of bentonites.The impact of phenol solution on the chemical compatibility of CTMAB-CMC-modified bentonite is lower than that of CMC-modified bentonite and unmodified bentonite.The resulting characteristic functional group and clay mineral(001)peak analysis shows that the partitioning effect is the main reason for enhancing the chemical compatibility of bentonite.After a TEM image analysis,it is found that the change in microstructure due to phenol solution of both modified bentonites is insignificant,and CTMAB-CMC-modified bentonite shows a relatively more dispersed structure compared to CMC-modified bentonite.