Acetaminophen degradation and byproduct formation in advanced oxidation processes using hydrogen peroxide or persulfate with graphene oxide-iron oxide

Graphene oxide (GO) loaded with magnetite (Fe3O4@GO) shows promise as a catalyst for advanced oxidation processes (AOPs). Fe3O4 generates free radicals by reacting with oxidants, while GO enhances the reaction. This study evaluated Fe3O4@GO with hydrogen peroxide (H2O2) and persulfate (S2O82−) for acetaminophen (APAP) degradation and examined the formation of harmful haloacetamides (HAMs) during subsequent chlorination and analyzes the evolving surface characteristics of the catalyst. The Fe3O4@GO/H2O2 system achieved 49% APAP removal after 1 h, primarily through adsorption onto Fe3O4@GO (23%) and direct oxidation by H2O2 (19%). It generated fewer radicals (•OH and SO4•–), resulting in a reduced potential for HAM formation during subsequent chlorination. In contrast, the Fe3O4@GO/S2O82− system showed a synergistic effect, with APAP removal attributed to adsorption onto Fe3O4@GO (23%), direct oxidation by S2O82− (7%), and AOP mediated by the Fe3O4@GO/S2O82− system (76%). This system also exhibited efficient radical generation, resulting in an increased HAM formation potential. Although H2O2 can work as both an oxidant and a reductant, it appeared to act mainly as a reducing agent in the presence of Fe3O4@GO. This interaction weakened the oxygen-containing functional groups of GO and caused Fe loss, thereby reducing the catalytic performance of GO/S2O82−. In contrast, S2O82− caused less structural damage to the catalyst, thereby enhancing its reusability. The Fe3O4@GO/S2O82− system maintained high APAP degradation efficiency over multiple reaction cycles, highlighting its potential for sustainable AOP applications.