Mechanism and performance of singlet oxygen dominated peroxymonosulfate activation on CoOOH nanoparticles for 2,4-dichlorophenol degradation in water

Peroxymonosulfate (PMS) has gained attention as oxidant for SR-AOPs. It is essential to develop a stable heterogeneous catalyst with strong hydrophilicity and high electron transfer capability for PMS activating. In this study, cobalt oxyhydroxide (CoOOH) was synthesized and activated PMS for degradation of 2,4-dichlorophenol (2,4-DCP) aiming to assess the feasibility of CoOOH/PMS system. 50 mg/L of 2,4-DCP could be 100% degraded within 120 min with 0.20 g/L CoOOH and 6 mM PMS. CoOOH/PMS system possessed a high degradation efficiency (0.0462 min-1), which was about 10 and 4 times higher than Co3O4/PMS and CoFe2O4/PMS system, respectively. Furthermore, it was found that CoOOH/PMS system displayed effective catalytic performance over broad pH range (e.g. 3-9). Importantly, the quenching tests revealed that 1O2 was identified as dominant reactive oxygen species (ROS). Co (Ⅲ) was rapidly reduced to Co (Ⅱ) owing to the efficient electron transfer rate performance of CoOOH in the catalytic reaction. Then, the regeneration of Co (Ⅱ) facilitated CoOH+ owing to the surface of CoOOH with sufficient hydroxyl group, which is crucial for PMS activation and reactive oxygen species-ROS generation. This study proposed an alternative technology based on peroxymonosulfate catalyzed by cobalt-based hydroxide for waste water treatment.