Synergistic oxidation-filtration process of electroactive peroxydisulfate with a cathodic composite CNT-PPy/PVDF ultrafiltration membrane

Ultrafiltration is an advanced water treatment process which performs poorly in the removal of small molecule organic pollutants, and is susceptible to irreversible membrane fouling. In this study, a new carbon nanotube cross-linked polypyrrole composite ultrafiltration membrane (CNT-PPy/PVDF) was fabricated, and exhibited excellent conductivity, hydrophilicity, and permeability in a novel electro-filtration activated peroxydisulfate (PDS) system (EFAP) for cathodic electrochemical activation of PDS. The EFAP showed satisfactory performance in removal of series of small molecule organic pollutants (i.e., carbamazepine, sulfamethoxazole, phenol, diclofenac.) and stable removal ratio (remaining above 90% after 20 operating cycles). Further study proved the electric field could effectively protect the cathodic CNT-PPy/PVDF membrane from oxidative damage through continual free electrons injection. Besides, the EFAP achieved up to 95% flux recovery and 80% reduction of irreversible membrane fouling (bovine serum albumin as the model foulant). Moreover, experiments confirmed that the in situ generated •OH, SO4•-, and 1O2 were the main reactive oxygen species contributing to small organics removal, while the irreversible membrane fouling mitigation was mainly due to the electrical repulsion, SO4•- and •OH, rather than 1O2. This new type of EFAP may provide a promising and sustainable approach in organic emerging contaminants control in water treatment.