Refractory organics removal in PMS and H2O2/PMS oxidation system activated by biochar/nZVI/MoS2 composite: Synthesis, performance, mechanism and dosing methods

A biochar composite loaded with nZVI particles and MoS2 nanosheets (nZVI/MoS2-BC) was prepared by calcination and hydrothermal methods, and could activate peroxymonosulfate (PMS) more efficiently to produce reactive oxygen species (ROSs) for refractory organics degradation. Due to the interaction between nZVI and MoS2, the reaction sites increased with nZVI dispersing more evenly and multitudinous MoS2 growing on the surface of biochar. PMS activated by nZVI/MoS2-BC produced SO4·-, ·OH, O2·- and 1O2 to degrade pollutants. In addition, the increase of specific surface area and electrical conductivity accelerated the electron transfer from pollutions to metastable PMS to achieve pollutant degradation. The effects of catalyst dosage, PMS dosage, pH, inorganic anions and humic acid, and Cl- concentration in catalytic oxidation system were investigated. nZVI/MoS2-BC was regenerated by calcination at 300 ℃ after four cycles, and could still keep higher rhodamine B (Rh-B) removal (90.88%). Various pollutants removal efficiency could reach greater than 80% in nZVI/MoS2-BC catalytic oxidation system, such as Rh-B, methylene blue, chloramphenicol, tetracycline and bisphenol A. The combination of H2O2 and PMS could greatly reduce the cost, improve the pollutant removal and shorten the reaction time by changing the interval time and content ratio of oxidants addition. nZVI/MoS2-BC applied to the H2O2/PMS double oxidation system exhibited excellent removal capability of pollutants. The intermediates of Rh-B were analyzed and the degradation pathways were proposed in nZVI/MoS2-BC and H2O2/PMS double oxidation system.