Cobalt oxide decorated activated carbon/peroxymonosulfate pretreatment for ultrafiltration membrane fouling control in secondary effluent treatment: Insights into interfacial interaction and fouling model transformation

To control the ultrafiltration (UF) membrane fouling caused by the secondary effluent, cobalt oxide loaded activated carbon (CoOx-PAC) activating peroxymonosulfate (PMS) was applied as a pretreatment. The degradation of natural organic matter (NOM) and membrane fouling mitigation performance for the CoOx-PAC/PMS pretreatment were comprehensively investigated. The dissolved organic carbon (DOC), fluorescent organics, and phenol in the secondary effluent system were utilized to evaluate the removal effect of the CoOx-PAC/PMS process on the organic matter. Results showed that 100 mg/L 0.5 %CoOx-PAC combined with 2 mM PMS (0.5 %CoOx-PAC/PMS) had an excellent degradation on NOM, removing 84.92 % of DOC, and above 97 % of fluorescent organics within 120 min. The catalytic activity of phenol in this process was even superior to that of homogeneous catalysis (Co2+/PMS). Moreover, the normalized specific flux and membrane fouling resistance were employed to verify the influences of the CoOx-PAC/PMS on membrane fouling. The 0.5 %CoOx-PAC/PMS system significantly improved the specific flux, with a 94.26 % decline in reversible membrane fouling resistance and a 53.05 % reduction in irreversible fouling resistance. O2•− and 1O2 were involved in the reaction as crucial reactive oxide species according to electron paramagnetic resonance and quenching tests. They changed the physicochemical properties of NOM, which decomposed the high molecular weight organics into low molecular weight hydrophilic fractions, thereby delaying the formation of cake layers and alleviating membrane fouling. The Extended Derjaguin-Landau-Verwey-Overbeek theory was used to assess the interaction between the foulants and the UF membranes. The transformation of fouling models was analyzed and found that the intricate membrane fouling filtration mechanisms were transformed into a single standard blocking mode after 0.5 %CoOx-PAC/PMS pretreatment.