Remediation of composite groundwater contaminants in petrochemical sites via lab-scale permeable reactive barriers

Composite groundwater contaminants at petrochemical sites were remediated via lab-scale PRBs. • Efficient oxidative removal of petrochemical hydrocarbons was achieved through enhanced Fenton-like reactions. • Metal ions and chlorinated hydrocarbons were removed via direct reduction with high electron transfer efficiency. • A sequential reduction-oxidation coupling strategy achieved complete mineralization of chlorinated nitroaromatic compounds. Petrochemical-contaminated sites are commonly characterized by complex mixtures of pollutants rather than a single target compound. However, these co-existing contaminants often differ substantially in reactivity and may therefore require distinct remediation pathways, which remains insufficiently addressed in conventional PRB design. In this study, we employed oxalate-modified ZVI (Ox-ZVI) as the PRB filler. By classifying and treating the typical composite contaminants at petrochemical sites according to their chemical properties, efficient and stable degradation of composite pollutants was achieved through laboratory column experiments. For typical composite pollutants including petroleum hydrocarbons, trichloroethylene and toluene, we applied a Fenton-like oxidation method and demonstrated the superior hydrogen peroxide activation capability and oxidative removal efficiency of Ox-ZVI. Regarding reducible pollutants containing metal ions and chlorinated hydrocarbons, we revealed a direct reductive removal mechanism and highlighted the high electron transfer efficiency of the iron core, while surface FeC 2 O 4 functioned as strong adsorption sites. Building on these findings, a sequential reduction-oxidation coupling strategy was further developed, which achieved efficient mineralization of chlorinated nitroaromatic compounds. During the 12-day continuous PRB operation, the Ox-ZVI system demonstrated stable performance and consistently outperformed conventional ZVI. This work offers a versatile and targeted technical pathway for the efficient remediation of complex petrochemical-contaminated sites. By classifying and treating typical composite contaminants at petrochemical sites, we achieved efficient and stable remediation of groundwater through laboratory PRB system filled with oxalate-modified ZVI. Download: Download high-res image (68KB) Download: Download full-size image