Enhanced Electrokinetic Remediation of Zn-Pb-Cd Co-Contaminated Soil Using a Surfactant-Modified Montmorillonite Permeable Reactive Barrier

Electrokinetic-Permeable Reactive Barrier (EK-PRB) technology can effectively remediate heavy metal-contaminated soil, and the properties of PRB materials play an important role in determining the remediation efficiency. To select a suitable PRB material, montmorillonite (MMT) was modified using cetyltrimethylammonium bromide (CTAB), sodium dodecylbenzenesulfonate (SDBS), and cocamidopropyl betaine (CAB), respectively; their remediation efficiencies for soils co-contaminated with Zn2+, Pb2+, and Cd2+ were then compared within an EK-PRB system. The results indicated that remediation efficacy varied significantly depending on the heavy metal and the surfactant used for modification. After 7 days of remediation, SDBS-modified MMT achieved the highest Zn2+ removal efficiency (49.65%), whereas CTAB-modified MMT showed optimal removal performance for both Pb2+ (38.03%) and Cd2+ (76.02%). When the remediation time was extended to 14 days, SDBS-modified MMT attained the highest removal efficiencies for Zn2+ (69.80%) and Pb2+ (69.50%), while CTAB-modified MMT maintained superior Cd2+ removal performance (86.94%). Energy consumption analysis showed that both CAB- and SDBS-modified MMT reduced energy consumption moderately compared with the unmodified control, whereas CTAB modification resulted in a substantial increase in energy demand. Experimental results confirm that surfactant-modified MMT effectively optimizes the EK-PRB remediation. A comprehensive evaluation considering both removal efficiency and energy consumption identified SDBS-MMT as the optimal material. The optimized EK-PRB parameters established in this study provide theoretical and technical support for the remediation of soils co-contaminated with multiple heavy metals.