铬污染土壤对水泥熟料强度和铬浸出浓度的影响

Effect of chromium-contaminated soil on strength and chromium ions leaching concentration of cement clinker

为探索水泥窑协同处置铬污染土壤(CCS)的可行性,用CCS部分替代硅质原料配制生料,于1 400℃煅烧成熟料,通过化学分析、强度测试、浸提实验及XRD/SEM分析,研究了CCS对生料易烧性、熟料强度及六价铬/总铬(Cr(VI)/∑Cr)浸出浓度的影响。结果表明,CCS能改善熟料烧成,掺量从0到15%,熟料中f-CaO含量略有下降,硬化试体的3 d、28d、90 d强度略有提高。Cr(VI)/∑Cr浸出浓度随CCS掺量增加而增大,但随养护龄期延长而减小;当CCS掺量小于8%时,熟料3 d至90 d水化物的浸出液中,Cr(VI)浓度均低于0.05 mg/L,符合II类地表水环境质量标准限值。铬离子浸出毒性减小是由于铬在熟料矿物和水化产物中的固溶以及水化产物对它的包裹封固作用。研究表明,水泥窑协同处置CCS是一种可行的无害化处理和资源化利用途径。

Cement kilns are capable to co-process a variety of solid industrial wastes. Here chromium-con- taminated soll （CCS） was taken as partial substitution of siliceous raw material to produce cement clinker at 1 400℃. Results indicate that CCS is beneficial to raw meal sintering. As adding quantity of CCS varies from 0 to 15% , f-CaO content of clinker reduces, while 3 d/28 d/90 d compressive strength of hardened cement paste increases. The more CCS is added, the higher leaching concentration of Cr（ VI）/~ Cr will be. Then the concen- tration drops off with the prolongation of cement paste＇ s curing time. According to GB 3828-2002, as CCS quan- tity increases to 8% , 3 -90 d leaching concentration of Cr（VI） is lower than the environmental quality standards of II surface water （0.05 mg/L）. The decrease of Cr（ VI）/~ Cr concentration should be attributed to solid solution of Cr in clinker mineral and its hydrate, then hydrate （C-S-H mainly） can wrap some Cr ions and prevent them from leaching. The innocuous treatment and utilization of CCS with cement kilns is available, and relevant research will be appreciated.