Coupled effects of Fenton-like systems with different concentrations of H2O2/Biochar on diethyl phthalate removal: Dominant role of environmental persistent free radicals (EPFRs)

To investigate the impact of different H 2 O 2 concentrations on the Fenton-like systems of H 2 O 2 /biochar, this study examined the mechanism of the physical structure and environmental persistent free radicals (EPFRs) of biochar during diethyl phthalate (DEP) removal by the Fenton-like system. The peak-splitting method was utilized to differentiate EPFRs types in cotton stalk biochar produced at different temperatures. High-temperature environments promote π-electron delocalization, which facilitates phenyl π free radicals and σ-π oxygen-containing free radicals. By analyzing relationships between the removal rate K 1 and removal constant K obs of DEP with the structural properties of biochar, it was discovered that EPFRs concentrations in biochar had a significant positive correlation with K 1 (r = 0.92) and K obs (r = 0.97). Different H 2 O 2 concentrations added to the biochar removal system resulted in varied DEP removal efficiency. Among them, CS 500 , CS 550 , and CS 600 exhibited superior DEP removal efficiency when H 2 O 2 concentration was 5 mM.