Insights into the effects of cobalt ferrite nanoparticles activated peroxymonosulfate on waste activated sludge dewaterability during ciprofloxacin degradation

Abstract

This research delved into the effect of cobalt ferrite nanoparticles activated peroxymonosulfate (CoFe2O4/PMS) treatment on sludge dewaterability during the ciprofloxacin (CIP) degradation in waste activated sludge (WAS). When the dosage of CoFe2O4 was 80 mg/g TSS and PMS was 60 mg/g TSS, the water content (Wc) of sludge was reduced from 80.84% to 66.33% while the capillary suction time (CST) of sludge descended from 82.6 s to 55.2 s. Considering cost and follow-up operations, the favorable pH for sludge dewatering was 6.9 additionally. During the process, the sludge disintegration brought out the dissolution of organic substances and the destruction of extracellular polymer substances (EPS). The results showed that both of soluble chemical oxygen demand (SCOD) and total nitrogen (TN) dissolved in the supernatant had a remarkable positive correlation with the sludge dewaterability. The strong oxidative free radicals SO4∙- (63.6%), ∙OH (28.2%), and ·O2- (6.3%) produced by CoFe2O4/PMS destructed the EPS structure, accompanied with proteins and polysaccharides oxidization as well as the bound and intracellular water release. There was also a significant positive relationship between polysaccharide ratio to protein and sludge dewatering (CST and Wc), which was consistent with that polysaccharide is more hydrophilic than protein. At last, a mechanism involving oxidization and re-aggregation has been presented, which is beneficial to the dewatering performance of sludge. This research underlines the potential of CoFe2O4/PMS as a promising technology for enhancing the sludge dewatering efficiency and degrading CIP, with significant implication for environmental protection.