Investigating the efficiency and mechanism of biochar in-situ reaction zones for groundwater remediation: A case study of 1,2-dichloroethane in gravel column

Dichloroethane (1,2-DCE), a common groundwater contaminant in petroleum extraction and refining areas, poses a threat to both the environment and nearby populations. To address this issue, a cost-effective and straightforward engineering approach is suitable for treating contaminated areas. In this study, nitrogen-doped biochar was prepared through an anoxic roasting modification method using sesame meal. At optimal dosage: 4.5 mM persulfate with 1.2 g/L N-SDB. The system achieved complete removal of 0.1 mM of 1,2-DCE within 90 min, with a total organic carbon (TOC) removal rate of 87.03 %. The biochar exhibited excellent stability, achieving 99.88 % removal of 0.1 mM 1,2-DCE and 76.13 % removal of TOC after six degradation cycles. The results indicated three main pathways for 1,2-DCE degradation, with hydroxyl radicals (·OH) and single-linear oxygen ( 1 O 2 ) as the main reactive species in the reaction system. Moreover, we developed a biochar in-situ reaction zone within a one-dimensional gravel column by optimizing particle size and injection concentration and conducted simulated remediation experiments on 1,2-DCE. The results revealed that all 1,2-DCE passing through the in-situ reaction zone was completely removed within 630 min.