Self-Neutralized Conditions Constructed by Amphoteric Zinc in Cobalt-Induced Peroxymonosulfate Activation for Sustainable Degradation of Organic Pollutants

Heterogeneous cobalt catalysts are universally used in advanced oxidation processes (AOPs) based on peroxymonosulfate (PMS) with a preference for neutral conditions. However, achieving neutral conditions in practice poses a challenge due to the acidic nature of PMS itself. In this study, we developed a method to create a neutral microenvironment at the interface of ZnCo carbonate hydroxide hydrate (ZnCo-CHH) by utilizing amphoteric Zn(OH)2. The ZnCo-CHH/PMS system demonstrated outstanding performance in phenol degradation and exhibited the ability to self-neutralize pH within a wide range of 3.0–11.0. This enhanced activity was attributed to the improved performance of PMS activation without modifying the oxidizing species in the presence of the neutral microenvironment. The effectiveness of this strategy was further validated on commercial CoO, Co3O4, and CoFe2O4, resulting in respective improvements of 98.2, 36.0, and 47.1% in PMS activation. In addition, the facile alkalization process utilized in long-term degradation was proved effective in reactivating the ZnCo-CHH and recovering the leaching cations. The successful treatment of actual wastewater, along with minimal impact from common anions and natural water resources, further supports the practical potential of this strategy. This research offers a universal approach to establish self-neutralized conditions for cobalt-based catalysts, thereby enhancing PMS activation without altering the oxidative species.