酸性干湿循环下铬污染土固化体浸出行为研究  

Leaching characteristics of solidified Cr-contaminated soil under acidic wet-dry cycles

作　　者：刘祥宁 张文杰 LIU Xiang-ning;ZHANG Wen-jie(School of Mechanics and Engineering Science,Shanghai University,Shanghai 200072,China;School of Civil Engineering and Architecture,Taizhou University,Taizhou,Zhejiang 318000,China)

机构地区：[1]上海大学力学与工程科学学院,上海200072 [2]台州学院建筑工程学院,浙江台州318000

出　　处：《岩土力学》2025年第4期1196-1204,共9页Rock and Soil Mechanics

基　　金：国家自然科学基金(No.52478353)。

摘　　要：干湿循环和酸雨侵蚀下污染土固化效果将产生劣化。针对碱激发高炉矿渣固化/稳定化的铬污染土进行酸性条件下的干湿循环试验,通过毒性浸出和加速浸出试验研究固化体中铬浸出规律和机制,通过扫描电子显微镜和能谱分析揭示微观机制,通过表观扩散系数评价长期稳定性。结果表明:中性pH下短期干湿循环后,高炉矿渣进一步水化,总Cr和Cr(Ⅵ)浸出浓度减小,随干湿循环次数增加生成了更多钙矾石,其膨胀产生微裂缝导致浸出增加;酸性干湿循环时,钙矾石首先溶解,通过置换作用,固定的Cr(Ⅵ)被释放,随酸性增强水化硅酸钙凝胶溶解,生成的石膏导致更多微裂缝,大量铬因包封作用减弱而浸出,而水化硫铝酸钙仍保持稳定。对数的累计浸出比例-时间斜率在0.373~0.675之间,使用纯扩散解析解拟合的误差基本小于0.5%,扩散是铬浸出的主导机制,但pH=3下18次干湿循环后溶解作用占比增加,不再满足扩散主导的判定标准。中性、弱酸性、强酸性干湿循环后固化体中铬的迁移性分别为低、中等、高,将固化土资源化利用时应采取措施减少酸雨入渗和干湿循环。研究为固化污染土长期稳定性评价提供了借鉴。The solidification effect of contaminated soil degrades under wet-dry(W-D)cycles and acid rain.Acidic dry-wet cycle tests for Cr-contaminated soil solidified by alkali-activated granulated blast furnace slag(GGBS)are carried out.Toxic leaching test and accelerated leaching test are performed to study the leaching characteristic and mechanism.Scanning electron microscopy and energy spectrum analysis are used to investigate the microscopic mechanism.The long-term stability is evaluated through the apparent diffusion coefficient.The results show that a few W-D cycles at pH=7 will cause additional hydraulic reaction of GGBS and thus reduce the leaching concentration of total Cr and Cr(Ⅵ).Along with W-D cycles more AFt is generated.The expansion of AFt results in micro-fracture and thus more Cr leaching.In acidic W-D cycles,AFt dissolves first,releasing Cr immobilized by ion exchange.With the increasing acidity,C-S-H gels dissolve and more gypsum is generated,resulting in more micro-fractures.Consequently,the encapsulation effect weakens,resulting in more Cr leaching.However,the C-A-S-H gels remain stable.The slopes of the logarithmic curves of cumulative leached fraction versus time range from 0.373 to 0.675.The errors of fitting by a pure-diffusion analytical solution are mainly below 0.5%,indicating that diffusion is the dominant leaching mechanism.However,after 18 W-D cycles at pH=3,the effect of dissolution increases and the diffusion-dominated criteria are not satisfied.The mobility of Cr under neutral,weak acidic,and strong acidic W-D cycles is low,moderate,and high,respectively.It is necessary to take measures to reduce acid rain infiltration and W-D cycles when utilizing solidified soil.This research provides a reference for evaluating the long-term stability of solidified contaminated soil.

关 键 词：铬污染土 固化/稳定化 长期稳定性 酸性干湿循环 加速浸出试验 

分 类 号：TU43[建筑科学—岩土工程]