Nickel ferrite-activated peroxydisulfate advanced oxidation process for enhanced sludge dewatering: performance evaluation and mechanism analysis

This study proposes a sustainable sludge dewatering strategy utilizing magnetic nickel ferrite (NiFe₂O₄, NFO) to activate sodium persulfate (Na₂S₂O₈, PDS) through advanced oxidation processes (AOPs). Systematic optimization of key operational parameters - including catalyst/oxidant mass ratio, pH, and reaction time - revealed that sulfate radicals (SO₄•⁻) played a dominant role in extracellular polymeric substances (EPS) degradation. This optimized AOPs-based conditioning achieved remarkable improvements in sludge dewaterability compared to raw sludge: water content (Wc) and specific resistance to filtration (SRF) were reduced by 12.8% and 81.6%, respectively. EPS characterization confirmed that SO₄•⁻ cleaved hydrophobic components (e.g. humic acids, aromatic proteins) in tightly bound EPS (TB-EPS), leading to a 46.28% reduction in bound water content and a marked increase in sludge hydrophilicity. The NFO catalyst exhibited robust recyclability, with a magnetic recovery rate exceeding 75% after four consecutive cycles and sustained catalytic activity. This work offers valuable mechanistic insights into persulfate-activated sludge conditioning and establishes a sustainable, economically feasible technology for sludge treatment.