State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China.
Key Laboratory of Rock Mechanics in Hydraulic Structural Engineering of the Ministry of Education, Wuhan University, Wuhan 430072, China.
Environ Sci Technol. 2022 Aug 16;56(16):11343-11353. doi: 10.1021/acs.est.2c01311. Epub 2022 Jul 29.
In situ chemical oxidation (ISCO) has proven successful in the remediation of aquifers contaminated with dense nonaqueous phase liquids (DNAPLs). However, the treatment efficiency can often be hampered by the formation of solids or gas, reducing the contact between remediation agents and residual DNAPLs. To further improve the efficiency of ISCO, fundamental knowledge is needed about the complex multiphase flow and reactive transport processes as new solid and fluid phases emerge at the microscale. Here, via microfluidic experiments, we study the pore-scale dynamics of trichloroethylene degradation by permanganate. We visualize how the remediation evolves under the influence of solid phase emergence and explore the roles of injection rate, oxidant concentration, and stabilization supplement. Combining image processing, pressure analysis, and stoichiometry calculations, we provide comprehensive descriptions of the oxidant concentration-dependent growth patterns of the solid phase and their impact on the remediation efficiency. We further corroborate the stabilization mechanism provided by phosphate supplement, which is effective in inhibiting solid phase generation and thus highly beneficial for the oxidation remediation. This work elucidates the pore-scale mechanisms during remediation of chlorinated solvents with a particular context in the solid phase production and the associated effects, which is of general significance to understanding various processes in natural and engineered systems involving solid phase emergence or aggregation phenomena, such as groundwater and soil remediation.
原位化学氧化 (ISCO) 已被证明在修复受密集非水相液体 (DNAPLs) 污染的含水层方面是成功的。然而，由于固体或气体的形成，处理效率往往会受到阻碍，从而减少了修复剂与残留 DNAPLs 之间的接触。为了进一步提高 ISCO 的效率，需要深入了解复杂的多相流和反应传输过程，因为在微尺度上会出现新的固、液相间。在这里，我们通过微流控实验研究了高锰酸盐降解三氯乙烯的孔隙尺度动力学。我们直观地了解了在固相出现的影响下修复是如何演变的，并探索了注入速率、氧化剂浓度和稳定化补充的作用。通过图像处理、压力分析和化学计量计算相结合，我们提供了对氧化剂浓度依赖性固相生长模式及其对修复效率影响的全面描述。我们进一步证实了磷酸盐补充提供的稳定化机制的有效性，它能有效抑制固相生成，从而对氧化修复非常有利。这项工作阐明了在含氯溶剂修复过程中的孔隙尺度机制，特别关注固相生成及其相关影响，这对于理解涉及固相出现或聚集现象的各种自然和工程系统中的过程具有普遍意义，如地下水和土壤修复。
