Photothermally-activated peroxymonosulfate (PMS) pretreatment for fouling alleviation of membrane distillation of surface water: Performance and mechanism

•Photothermally-activated PMS pre-treatment was applied for MD fouling alleviation.•NOM in the surface water can be effectively removed after PMS pre-treatment.•Stable permeance (PMS (2 mM)) vs 50 % reduction (control) of flux were obtained.••OH and SO4•− radicals generated by PMS contributed to the NOM removal.•The MD membrane properties could be kept conserved by the PMS pre-treatment step.