Pyrolysis characteristics of biochar composite loaded with Fe(III) and its activation mechanism to persulfate

Although metals (Fe(III)) loaded with BC (MBC) exhibited good catalytic reactivity, the structural evolution process of MBC with pyrolysis and the evaluation of electron transfer capacity of MBC during persulfate oxidation were typically overlooked. Results of this study indicated that increasing pyrolysis temperature could promote the carbonization of biomass and lead to the formation of a well-developed microporous structure. Large numbers of functional groups and Fe species were formed by pyrolysis, but the content varies greatly under different pyrolysis temperatures. MBC prepared at pyrolysis temperature of 300 °C (MBC300) exhibited an excellent activation capacity, and the removal efficiency of 2,4-dinitrotoluene reached 83.7% within 5 h of the reaction by adding in 2.5 mmol/L persulfate and 0.5 g/L MBC300. Sulfate radical (SO 4 ·- ) and hydroxyl radical (·OH) participated in the reaction, but ·OH was mainly responsible for the degradation of 2,4-dinitrotoluene. Multiple characterization methods confirmed that Fe(III) maghemite and Fe 2p1/2 in MBCs mainly promoted the activation of persulfate, and oxygen-containing functional groups as an electronic shuttle accelerated the electron transfer in the persulfate/MBC system. Compared to that of biochar, the electron donating and electron accepting capacity of MBC were increased by an order of magnitude. This result is of significance for the preparation of green activation material used in the remediation of organically polluted groundwater with persulfate oxidation.