Piezoelectric Activation of Peroxymonosulfate by CoMn2O4 for Highly Efficient Tetracycline Degradation

Advanced oxidation processes employing peroxymonosulfate (PMS) show significant promise for wastewater treatment. However, PMS activation typically relies on energy- and chemically intensive techniques due to its relatively low reactivity. Hence, the exploration of novel and energy-efficient approaches, such as the piezoelectric effect, for PMS activation is of paramount importance. Herein, we prepared a piezoelectric material (CoMn2O4) via a simple hydrothermal method followed by calcination. The degradation experiments of tetracycline (TC) demonstrated that CoMn2O4 exhibited excellent performance under ultrasound, the apparent rate constant k is 0.191 min–1, and its degradation rate reached 83.63% after 10 min. Piezo force microscopy (PFM) tests confirmed that CoMn2O4 exhibited a piezotronic effect under ultrasound. In situ electron paramagnetic resonance (in situ EPR) tests revealed that PMS could be activated to form hydroxyl radicals (•OH) and sulfate radicals (SO4•–) under ultrasound, which are active species for TC degradation. Consequently, CoMn2O4 effectively activated PMS into •OH and SO4•– active species, enabling the effective TC degradation. Moreover, biotoxicity experiments using germination tests showed that CoMn2O4 was capable of effectively degrading TC, thereby reducing environmental toxicity. This work not only provides mechanistic insights into piezoelectric material-activated PMS for pollutants degradation but also establishes a basis for the application of piezoelectric materials in pollutant degradation.