Unveiling the kinetics and mechanism of sulfide-modified zero-valent iron activated hydrogen peroxide for phenol degradation

In this study, sulfide-modified zero-valent iron (S-ZVI) synthesized by a two-step process with optimal S/Fe ratio of 0.056 was used to activate hydrogen peroxide (H2O2) 2 O 2 ) to degrade phenol, and the kinetics and reaction mechanism of phenol degradation were investigated under different conditions. Phenol degradation kinetics in SZVI/H2O2 2 O 2 system was characterized by an initial lag phase followed by a rapid reaction period, which was accurately described by Logistic regression model, deviating from conventional pseudo-first-order and pseudo- second-order models. Over 80 % of phenol degradation occurred via liquid-phase reactions, predominantly driven by hydroxyl radicals (center dot OH). The consumption of H2O2 2 O 2 and the removal of total organic carbon (TOC) were both significantly correlated with the total dissolved iron content, underscoring the importance of iron dissolution. The S-ZVI/H2O2 2 O 2 system outperformed other activated H2O2 2 O 2 systems, with a 41.71 %, 35.89 %, and 44.02 % increase in H2O2 2 O 2 utilization efficiency for TOC removal compared to FeSO4, 4 , ZVI, and ZVI(H+), + ), respectively. Sulfide-modification of ZVI significantly promoted the sustained release of dissolved iron with a higher proportion of Fe2+, 2+ , which was identified as a key factor in enhancing H2O2 2 O 2 utilization efficiency. Our findings provide new insight into a better description of the pollutant removal kinetics process in the S-ZVI/H2O2 2 O 2 system and the synergistic effects between S-ZVI and H2O2 2 O 2 for organic pollutant degradation.