Comparative study of organic removal by pre-adsorption oxidation and synchronous adsorption oxidation processes: performance and mechanism

Both adsorption and oxidation occur and contribute to organics removal in carbonaceous materials based advanced oxidation processes, while the correction of adsorption and oxidation, and the role of adsorption in the veritable removal of organic are not clear. Herein, we investigated the performance of carbamazepine (CBZ) removal by peroxymonosulfate (PMS) activated by magnetic Fe-doped biochar in two models of pre-adsorption oxidation and synchronous adsorption oxidation processes. The adsorption process was better fitted by pseudo-second-order kinetic model and the adsorption mechanism was obtained by comprehensive analysis of equilibrium adsorption capacities, surface functional groups, specific surface area, pore volume, and ID/IG value. It is noted that pre-adsorption highly inhibited the further oxidation of CBZ in 0.5Fe@LSBC700/PMS system due to the occupied catalytic active sites. Total CBZ removal in pre-adsorption oxidation (45%) was inferior to synchronous adsorption oxidation (~100%), as well as the veritable CBZ oxidation removal of 27% for pre-adsorption oxidation vs ~100% in synchronous adsorption oxidation at 30 min. Oxidation degradation of CBZ based on radical oxidation was identified by quenching experiments and electron paramagnetic resonance measurements. This work is conducive to identifying the role of adsorption during the removal of organics in the adsorption-oxidation process, as well as veritable adsorption and oxidation removal of organics. The relationship between adsorption and catalytic oxidation, and their virtual contribution to pollutant removal in heterogeneous biochar composite materials activated AOPs is lacking. How to choose a suitable model of pre-adsorption oxidation or synchronous adsorption oxidation to achieve an excellent veritable organic removal is blurry. Herein, magnetic Fe-doped biochar composites were synthesized and used for PMS activation with CBZ as the targeted compound through pre-adsorption oxidation process and synchronous adsorption oxidation processes. Especially, the apparent CBZ removal, veritable CBZ adsorption removal, and veritable CBZ oxidation removal were calculated and clarified. The detailed adsorption and catalytic oxidation mechanisms were elucidated.