铜对硒(Ⅳ)在高庙子膨润土中吸附行为的影响

Effects of Cu on the sorption of selenite in Gaomiaozi bentonite

硒-79是高放废物(HLW)地质处置库安全评价中重点关注的放射性核素之一.在多重屏障体系中,高放废物外包装起到隔离放射性废物和地下水的作用.已有国家把铜作为废物包装容器的备选材料,如瑞典、芬兰等,而我国还未确定废物包装容器材料.因此,研究不同价态的铜与硒(Ⅳ)的相互作用可为我国废物包装容器材料选取提供支持.本文使用批式吸附实验法探究了不同价态的铜对硒(Ⅳ)在高庙子膨润土上吸附的影响,结果表明,在碱性条件下硒(Ⅳ)在膨润土上的吸附百分比小于20%,而引入CuCl2后,硒的吸附百分比可达100%.进一步研究发现,硒在铜(Ⅱ)的水解产物氯铜矿上有很强的吸附.膨润土可与氯铜矿发生相互作用,减弱硒(Ⅳ)在氯铜矿上的吸附,在c(Se)=10-4 mol·L-1,pH=6时,引入膨润土后硒的吸附百分比从97%降至70%.在酸性条件下低价态铜,如CuCl、Cu和Cu2O等可将硒(Ⅳ)还原到低价态(0,-I,-II),使得硒的吸附百分比从8%提高到90%以上,促进了硒的吸附.在含CuCl、Cu和Cu2O的3种体系中,硒在含CuCl的体系有最快的吸附速率.

Se-79 is one of the key radionuclides in the safety assessment of high-level radioactive wastes(HLW)repository.In the multiple barrier system,the canister is set to separate solid waste from ground water.Copper is a spare material for canister in Sweden and Finland,and China has not chosen the material for canister yet.Therefore,studies on the interactions of selenite with different valence states of Cu can provide information for the selection of canister material in China.In this work,we investigate the effects of different valence states of Cu on selenite sorption in Gaomiaozi bentonite with batch experiment.The results show that under alkaline condition,selenite sorption percentage was below 20%.When CuCl2 was introduced into this system,selenite sorption percentage reached 100%.Atacamite,the hydrolysate of CuCl2,had strong affinity for selenite.Bentonite interacted with atacamite,and reduced the sorption percentage of selenite from 97%to 70%at pH 6,c(Se)=10-4 mol·L-1.Under acidic condition,Cu with lower valence such as CuCl,Cu and Cu2O reduceed selenite into Se(0,-Ⅰ,-Ⅱ),which increased the sorption percentage of selenite onto bentonite from 7.6%to over 90%.Selenite sorption was the most rapid in the systems containing CuCl among the system containing CuCl,Cu and Cu2O.