Regeneration of saturated activated carbon by electro-peroxone and ozonation: Fate of micropollutants and their transformation products

Abstract Many micropollutants (MPs) that may adversely affect aquatic life when released into the environment are common in modern societies. The presence of MPs in the environment is frequently connected to release from wastewater treatment plants. Therefore, advanced treatments are needed to remove these MPs. Powdered activated carbon (PAC) efficiently removes MPs in both laboratory experiments and full-scale applications. However, its single-use nature and the difficulty of handling spent PAC has limited the popularity of this approach. Therefore, various methods for PAC regeneration have been investigated. The current study compares two methods for regenerating spent PAC saturated with MPs: ozonation and the electro-peroxone (E-peroxone) process. Six MPs were tested: benzotriazole, carbamazepine, ciprofloxacin, diclofenac, perfluorooctanoic acid (PFOA), and trimethoprim. Both methods achieved regeneration efficiencies (REs) of >100% for four of the MPs. However, the REs for diclofenac (95–102%) and PFOA (67–69%) were below 100%. Surface characterization showed that PAC regeneration did not restore the micro- and mesopores that are mainly responsible for MPs sorption by virgin PAC. Instead, MPs sorption onto regenerated PAC was determined to be related to different interactions between PAC surface and MPs' ionic states including electrostatic, H-bonding, and electron donor-acceptor interactions. Transformation products of adsorbed MPs typically remained sorbed on the regenerated PAC rather than being transferred to the regeneration effluent.