Performance of persulfates activated by agricultural waste-derived biochar for the removal of pentachlorophenol in groundwater

Biochar (BC) is an emerging material produced by the pyrolysis of biomass and has been used for various environmental applications. In this study, BC prepared from rice husk waste was employed to activate peroxymonosulfate (PMS) and peroxydisulfate (PDS) for the removal of pentachlorophenol (PCP) in groundwater. Specifically, the removal kinetics was investigated, the influences of groundwater matrix were examined, and the removal mechanism was explored. The results showed that the prepared BC could only activate PMS to degrade PCP while PDS could not be activated by the BC. The rate of PCP removal increased with the increasing PMS concentration and BC loading, in which more than 85% removal can be achieved in 90 min. Radical quenching experiments and electron paramagnetic resonance studies indicated that singlet oxygen (1O2) was responsible for the degradation of PCP in the PMS system. The presence of HCO3− and humic acid appeared to inhibit the removal of PCP under groundwater conditions. Reusability tests showed that the performance of PCP removal decreased after four cycles but calcination regeneration at 150 °C for 30 min was effective to recover the PMS activation capacity of BC.