The isolated Ca-Nx sites in biochar boosting Fe catalyzed Fenton-like oxidation of Tris(2-chloroethyl) phosphate: Properties, mechanisms, and applications

The biochar with single Ca atom (1.7 wt%) loaded nanoscale zero-valent iron composites (Fe@Ca-N-C) were prepared and effectively degraded tris(2-chloroethyl) phosphate (TCEP) via Fenton-like oxidation. Systematic experiments and theoretical calculations indicated that the enhanced removal of TCEP was attributed to the synergistic effect of adsorption (Ca-N x sites) and degradation (Fe sites). Remarkably, the optimal system of 0.1 g L −1 Fe@Ca-N-C, 1 mM peroxydisulfate (PDS) achieved 99.5 % TCEP degradation (2 mg L −1 ) in 30 min and maintained 100 % TCEP removal for 72 h in continuous-flow reaction column. The Ca-N x sites exhibited high adsorption energy for TCEP (especially the Ca-N 1 sites), and the Fe sites (Fe(0) and Fe(Ⅱ)) activated PDS into HO•, which quickly degrades the adsorbed TCEP through C-O bond breaking and C-Cl bond hydroxylation. This study provided insights into single Ca atom utilization and TCEP pollution remediation.