酸性干湿循环下赤泥-石灰固化镉铅污染土性能

Properties of Red Mud-Lime Solidified Cadmium and Lead Contaminated Soil under Acidic Dry-Wet Cycle

为实现固废资源化利用并达到以废治废,变废为宝的目的,提出采用赤泥-石灰作为固化剂对镉、铅重金属污染土进行固化/稳定化处理,通过酸性干湿循环试验、无侧限抗压强度试验、毒性浸出试验以及微观结构分析,研究不同固化剂配比、污染物浓度、溶液pH值和干湿循环次数对赤泥-石灰固化剂固化污染土的质量损失率、强度变化、毒性浸出浓度以及微观形态的影响。结果表明:在各种条件下,R4C4固化土质量损失率最低;在溶液pH值为7、干湿循环下,固化土抗压强度随石灰掺量增加而增加,随循环次数的增加先增大后减小,在循环次数为两次时达到峰值;溶液pH值减小时,强度也随之减小;浸出浓度随循环次数以及溶液pH值的增大而增大,在初始浓度为M1时所有试样均满足标准要求;在多次酸性干湿循环后土体出现裂缝,且水化物减少导致结构被破坏。

To achieve the goal of utilizing solid waste resources and turning waste into treasure,red mud-lime was proposed as a solidifying agent for the solidification/stabilization treatment of cadmium and lead heavy metal contaminated soil.The effects of different ratios of solidifying agents,pollutant concentrations,solution pH values,and dry-wet cycle times on mass loss rate,strength change,toxicity leaching concentration and microstructural morphology were studied through acid dry-wet cycle tests,unconfined compressive strength tests,toxicity leaching tests,and microscopic structure analysis.Results showed that R4C4 solidified soil had the lowest mass loss rate under various conditions.Under the dry-wet cycle with solution pH=7,the compressive strength of the solidified soil increased with the increase of lime content.As the cycle times increased,the strength increased first and then decreased,reaching a peak at two cycles.As the pH value of the solution decreased,the strength also decreased.The leaching concentration increased with the increase of the cycle times and the pH value of the solution.All samples met the standard requirements at initial concentration M1.After multiple wet-dry cycles,cracks appeared in the soil and reduced hydration products led to structural damage.