Study on the microscale structure and barrier mechanism of magnesium phosphate cement modified with fly ash cutoff walls for lead pollution in groundwater
Study on the microscale structure and barrier mechanism of magnesium phosphate cement modified with fly ash cutoff walls for lead pollution in groundwater
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粉煤灰防渗墙改性磷酸镁水泥微观结构及阻隔地下水铅污染机理研究
DOI：
10.1016/j.conbuildmat.2021.124994
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发表时间：
2021-11
影响因子：
7.4
通讯作者：
Bing Liao
中科院分区：
文献类型：
--
作者：
Ji Xing;Changwen Ye;Jinqiu Zhou;Kui He;Rui Zhu;Hang Xiang;Jiancheng Liu;Zhenbin Xie;Bing Liao
•合成了粉煤灰改性磷酸镁水泥，作为一种新型截流壁材料。•最佳试样的渗透性满足防渗和力学要求。•通过孔隙尺度建模分析内部结构参数。•采用格子玻尔兹曼方法对渗透率和速度场进行了模拟。•利用Visual MODFLOW模拟了防渗墙对地下水铅的控制效果。合成了磷酸镁水泥-粉煤灰（MPC-FA）作为防治地下水铅污染的新型截流壁材料。通过一系列实验研究了磷酸镁水泥-粉煤灰截流墙对Pb（Ⅱ）的吸附、力学性能、形貌、微观结构和迁移等性能。采用x射线微计算机体层析成像技术，获得了断流壁的微尺度三维真实几何图像。通过数字图像处理技术对其内部结构参数进行分析。采用点阵玻尔兹曼方法（Lattice Boltzmann method， LBM）模拟了截流墙的导流率和三维速度场分布。最佳截流壁粉煤灰质量比为40%，磷酸二氢钠/磷酸二钾摩尔比为1:1。14 d的抗压强度为23.2 MPa，抗折强度为5.6 MPa。MPC-FA的实验水导率为1.22 × 10−9 m/s，理论最大吸附量为467.87 mg/g。孔隙网络模型表明，MPC-FA的连通孔隙度为14.45%，截流壁上的孔隙和喉道以半径≤12 μm的微流道为主。LBM模拟的导水率与实测结果基本吻合，流速场表明水流路径曲折复杂。在不同的突破浓度标准下，初始浓度为4000 mg/L的Pb（Ⅱ）穿透厚度分别为0.6 m、1 m、1.2 m、1.5 m的截流壁所需时间分别为8 ~ 10年、22 ~ 28年、31 ~ 41年和49 ~ 64年。通过Visual MODFLOW数值模拟得到的模型显示，在设置了MPC-FA截流墙的污染场地，7400天后污染物的铅羽（Ⅱ）得到了控制，说明MPC-FA达到了铅污染场地良好控制Pb（Ⅱ）的要求。
• Magnesium phosphate cement modified with fly ash was synthesized as a kind of novel cutoff wall material. • Permeability of the optimal sample can meet the anti-seepage and mechanical requirement. • Internal structural parameters were analyzed through the pore-scale modeling. • Permeability and velocity filed were simulated using the Lattice Boltzmann Method. • The control effect of cutoff wall on Pb in groundwater was simulated by Visual MODFLOW. Magnesium phosphate cement-fly ash (MPC-FA) has been synthesized as a new cutoff wall material to control lead pollution in groundwater. A series of experiments were conducted to investigate its properties including adsorption, mechanical performances, morphologies, microstructure and migration of Pb(Ⅱ) through the magnesium phosphate cement-fly ash cutoff walls. X-ray microcomputed tomography was used to get the microscale three-dimensional real geometry images of the cutoff walls. The internal structural parameters were analyzed through digital image processing technology. Lattice Boltzmann method (LBM) was employed to simulate the hydraulic conductivity and three-dimensional velocity fields distribution of cutoff walls. The optimized fly ash ratio (in mass) of cutoff walls was 40%, and the sodium dihydrogen phosphate/monopotassium phosphate molar ratio was 1:1. The compressive strength and flexural strength during 14 days were 23.2 MPa a nd 5.6 MPa, respectively. The laboratorial hydraulic conductivity of MPC-FA was 1.22 × 10 −9 m/s and the theoretical maximum adsorption capacity was 467.87 mg/g. The pore-network model showed that the connected porosity of MPC-FA was 14.45%, and the most of the pores and throats in cutoff walls were microflow paths (radius ≤ 12 μm). The hydraulic conductivity simulated by LBM basically coincided with the measured results, and the velocity fields indicated that the flow paths were tortuous and complex. Under different breakthrough concentration standards, the penetration of Pb(Ⅱ) at initial concentration of 4000 mg/L through cutoff walls with thickness of 0.6 m, 1 m, 1.2 m, 1.5 m needed 8–10, 22–28, 31–41 and 49–64 years, respectively. The model obtained by Visual MODFLOW numerical simulation showed that the contaminant plume of Pb(Ⅱ) was controlled after 7400 days in the polluted site with MPC-FA cutoff walls, which supported that the MPC-FA met the requirements for good control of Pb(Ⅱ) in the lead-contaminated sites.
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影响因子：
11.4
作者：
Yang, QB;Wu, XL
通讯作者：
Wu, XL
DOI：
10.1080/15320380500180440
发表时间：
2005-09
期刊：
Soil and Sediment Contamination: An International Journal
影响因子：
--
作者：
I. Lo;Jianhong Zhang;Liming Hu
通讯作者：
I. Lo;Jianhong Zhang;Liming Hu
影响因子：
7.4
作者：
Fan Shijian;Chen Bing
通讯作者：
Chen Bing
影响因子：
3.9
作者：
Wenjing Qin;Dongmei Han;Xianfang Song;P. Engesgaard
通讯作者：
Wenjing Qin;Dongmei Han;Xianfang Song;P. Engesgaard
影响因子：
11.4
作者：
SEEHRA, SS;GUPTA, S;KUMAR, S
通讯作者：
KUMAR, S