Comparative study of tetracycline degradation efficiency using peroxydisulfate activated with sludge biochar and activated coke: the role of surface defects

Abstract

Both sludge biochar (BC) and activated coke (ACO) are hierarchical while their surface properties have a large disparity. We show that sludge biochar pyrolyzed at 600°C (BC600) outperforms biochar produced at other temperatures for a range of biomass feedstock. BC600 displays lower carbon content, lower surface area, and importantly more abundant surface oxygen-containing functional groups when compared with ACO. BC600 and ACO were used to activate peroxydi - sulfate (PDS) for tetracycline oxidation while the degradation mechanisms were comprehen - sively discussed. Interestingly, ACO demonstrated a particularly higher performance where activating PDS compared with BC600. The K app value for the synergetically combined ACO-PDS process was 2.15 times that of the sum of adsorption and PDS oxidation processes alone, while it was 1.72 times for the BC600-PDS process. Solution pH had a more dramatic influence on BC600 than on ACO. Quenching experiments proved that both OH • and SO 4 •– contributed insignificantly while most of the degradation was attributed to superoxide radical (O 2 •– ), singlet oxygen ( 1 O 2 ), and active holes (h + ). After reducing carbonyl groups on both carbons by KBH 4 in absolute alcohol, quenching experiments did not indicate the key role of carbonyl groups for 1 O 2 generation. Non-radical pathway proved dominant in the carbon/PDS catalytic process. Excellent reusability and stability for ACO was observed in repeated use experiments.