Enhanced peroxymonosulfate activation for carbamazepine degradation under strongly alkaline conditions using Cu-doped Mn3O4 catalyst: Characterization, catalytic performance, and mechanism insights

Abstract

Activation of peroxymonosulfate (PMS) under strongly alkaline conditions for pharmaceutical removal faces the obstacle of activity because SO52− is the predominant form of PMS, which makes it difficult to be activated for radical generation. In this study, we designed Cu-doped Mn3O4 as a heterogeneous catalyst for PMS activation to degrade carbamazepine (CBZ) under alkaline conditions. Remarkably, at low catalyst dosage (30 mg/L) and low PMS dosage (100 mg/L), complete removal of CBZ (100%) was achieved within 5 min in the Cu1.5Mn1.5O4/PMS system at pH 11. The kinetic constant for CBZ degradation was determined to be 1.128 min−1, which is 94.0 times higher than that of the Mn3O4/PMS system. SO4∙-, ∙OH, and 1O2 were generated in the Cu1.5Mn1.5O4/PMS system, with SO4∙- playing a key role in CBZ degradation. The Cu site in Cu1.5Mn1.5O4 was identified as the active site responsible for PMS activation. Cu doping enhanced the –OH group generation and electron transfer of Cu1.5Mn1.5O4, leading to its high catalytic activity towards SO52−. The generation of free radicals was found to be associated with the Cu(I)/Cu(II) cycle, while Mn(III) promoted the redox cycle of Cu(I)/Cu(II). The Cu1.5Mn1.5O4/PMS system exhibited sustained activity and stability even after undergoing five cycles of recycling (>95% CBZ removal). Overall, the present study provides a novel system with superior performance for strongly alkaline pharmaceutical wastewater treatment.