巯基功能化沸石吸附Hg^(2+)特征及固化/稳定化含汞废物研究

Characteristics of mercury sorption and stabilization/solidification of mercury-contaminated hazardous wastes by thiol-functionalized zeolites

采用3-巯基丙基三甲氧基硅烷在天然斜发沸石表面进行自组装巯基改性,制得巯基功能化沸石.研究了吸附剂用量、pH值、温度、Hg2+浓度和吸附时间对巯基功能化沸石吸附Hg2+的影响,测定了巯基含量,并进一步研究了吸附机理.同时,探讨了巯基功能化沸石吸附剂作为稳定化剂固化/稳定化含汞危险废物的可行性.结果表明,巯基功能化沸石具有较高的巯基含量(1.91%±0.01%),对Hg2+的吸附容量为87.72mg·g-1,比天然沸石对Hg2+的吸附容量(8.06mg·g-1)提高了近10倍.巯基功能化沸石吸附Hg2+的机制主要是表面的巯基与Hg2+的反应,其受pH值、温度的影响小于天然沸石.动力学实验结果表明,巯基功能化沸石吸附Hg2+以较快的速率进行,3h时基本达到吸附平衡.巯基功能化沸石做稳定化剂能够促进汞的稳定,与单独使用水泥相比固化体浸出汞浓度显著降低,含汞1000mg·kg-1的模拟废物固化体浸出汞浓度低于国家标准.

3-Mercaptopropyltriethoxysilane was used to graft the thiol group（—SH）onto natural clinoptilolite zeolites to enhance their mercury adsorption capacity. Our objectives are to evaluate the effects of sorbent dosage,pH values,temperature,adsorption time and Hg^2＋ concentration on mercury adsorption by thiol modified zeolite,to analyze the amounts of —SH group,and then to further explore the adsorption mechanism. Also,the feasibility of thiol-functionalized zeolites used to stabilize mercury in solid waste was studied. The amount of —SH in the thiol-functionalized zeolite was as high as 1.91% 0.01% and it had a 87.72 mg·g^-1 adsorption capacity for Hg^2＋ which was 10 times higher than that of the natural clinoptilolite zeolites. The mercury retention by thiol-functionalized zeolite was attributed to the reaction between mercury and —SH group in the thiol-functionalized zeolites,and pH and temperature had less influence on the capacity than that of the natural zeolite. With a high adsorptive rate,the modified zeolite took 3h to reach the adsorption equilibrium. Thiol-functionalized zeolites can improve stabilization of Hg in the waste surrogate and greatly lower the mercury concentration in the leaching filtrate for S/S treated waste. Treated surrogate containing 1000 mg·kg^-1 Hg can successfully pass the leaching test.