Zhang Yuting, Boparai Hardijleet K, Wang Jinguo, Sleep Brent E
School of Earth Science and Engineering, Hohai University, No.8 Focheng West Road, Nanjing 211100, China; Department of Civil & Mineral Engineering, University of Toronto, 35 St. George Street, Toronto, ON M5S 1A4, Canada.
Department of Civil & Mineral Engineering, University of Toronto, 35 St. George Street, Toronto, ON M5S 1A4, Canada.
J Hazard Mater. 2022 Mar 15;426:127785. doi: 10.1016/j.jhazmat.2021.127785. Epub 2021 Nov 13.
Research on electrokinetics-permeable reactive barrier (EK-PRB) remediation to date has mainly focused on homogeneous soils or soils with micro-scale heterogeneities. The potential impact of macro-scale physical heterogeneities, such as stratified layers or lenses, on EK-PRB remediation has not received much attention. This study investigates the effect of a low permeability stratum on EK-PRB remediation of hexavalent chromium (Cr(VI)). Sandbox experiments were conducted to treat Cr(VI)-contaminated kaolinite/sand media, consisting of vertically-layered high permeability (HPZ) and low permeability zones (LPZ), where distance between LPZ and anode (DLA) was 3, 9, or 15 cm. Parameters including current, moisture content (MC), pH, and removal of Cr(VI) were evaluated. With 72 h of EK-PRB treatment, tests with larger DLA (15 cm) had greater Cr(VI) migration from contaminated area to modified-zeolite PRB. Cr(VI), Cr(III), and Cr(Total) removal and energy utilization efficiency followed the trend as: DLA-15 > DLA-9 > DLA-3. MC generally decreased from anode towards cathode and pH was alkaline in all the zones for DLA-3 and DLA-15. In DLA-9 (LPZ in the middle), MC increased and pH was alkaline in HPZs near cathode whereas HPZs near anode were very dry (MC < 1%) and acidic (pH < 5.5). Our results show that the location of LPZ relative to electrode locations has a significant influence on Cr(VI) removal efficiency and macro-scale physical heterogeneity is an important factor to be considered during EK-PRB remediation.
迄今为止，关于电动渗滤反应墙（EK-PRB）修复技术的研究主要集中在均质土壤或具有微观尺度非均质性的土壤上。宏观尺度的物理非均质性，如分层或透镜状地层，对EK-PRB修复的潜在影响尚未得到足够的关注。本研究调查了低渗透层对六价铬（Cr(VI)）的EK-PRB修复效果的影响。进行了砂箱实验，以处理受Cr(VI)污染的高岭土/砂介质，该介质由垂直分层的高渗透区（HPZ）和低渗透区（LPZ）组成，其中LPZ与阳极之间的距离（DLA）为3、9或15厘米。评估了包括电流、含水量（MC）、pH值和Cr(VI)去除率等参数。经过72小时的EK-PRB处理，DLA较大（15厘米）的试验中，Cr(VI)从污染区域向改性沸石PRB的迁移量更大。Cr(VI)、Cr(III)和总铬（Cr(Total)）的去除率以及能量利用效率遵循以下趋势：DLA-15 > DLA-9 > DLA-3。MC一般从阳极向阴极降低，对于DLA-3和DLA-15，所有区域的pH值均呈碱性。在DLA-9（LPZ在中间）中，阴极附近的HPZ中MC增加且pH呈碱性，而阳极附近的HPZ非常干燥（MC < 1%）且呈酸性（pH < 5.5）。我们的结果表明，LPZ相对于电极位置对Cr(VI)去除效率有显著影响，宏观尺度的物理非均质性是EK-PRB修复过程中需要考虑的重要因素。
