Piezoelectric\nActivation of Peroxymonosulfate by CoMn<sub>2</sub>O<sub>4</sub> for\nHighly Efficient Tetracycline Degradation

Advanced oxidation processes employing peroxymonosulfate\n(PMS)\nshow significant promise for wastewater treatment. However, PMS activation\ntypically relies on energy- and chemically intensive techniques due\nto its relatively low reactivity. Hence, the exploration of novel\nand energy-efficient approaches, such as the piezoelectric effect,\nfor PMS activation is of paramount importance. Herein, we prepared\na piezoelectric material (CoMn<sub>2</sub>O<sub>4</sub>) via a simple\nhydrothermal method followed by calcination. The degradation experiments\nof tetracycline (TC) demonstrated that CoMn<sub>2</sub>O<sub>4</sub> exhibited excellent performance under ultrasound, the apparent rate\nconstant <i>k</i> is 0.191 min<sup>–1</sup>, and\nits degradation rate reached 83.63% after 10 min. Piezo force microscopy\n(PFM) tests confirmed that CoMn<sub>2</sub>O<sub>4</sub> exhibited\na piezotronic effect under ultrasound. <i>In situ</i> electron\nparamagnetic resonance (<i>in situ</i> EPR) tests revealed\nthat PMS could be activated to form hydroxyl radicals (<sup>•</sup>OH) and sulfate radicals (SO<sub>4</sub><sup>•–</sup>) under ultrasound, which are active species for TC degradation.\nConsequently, CoMn<sub>2</sub>O<sub>4</sub> effectively activated\nPMS into <sup>•</sup>OH and SO<sub>4</sub><sup>•–</sup> active species, enabling the effective TC degradation. Moreover,\nbiotoxicity experiments using germination tests showed that CoMn<sub>2</sub>O<sub>4</sub> was capable of effectively degrading TC, thereby\nreducing environmental toxicity. This work not only provides mechanistic\ninsights into piezoelectric material-activated PMS for pollutants\ndegradation but also establishes a basis for the application of piezoelectric\nmaterials in pollutant degradation.