Novel halloysite nanotube-based ultrafine CoMn₂O₄ catalyst for efficient degradation of pharmaceuticals through peroxymonosulfate activation

In this study, a highly efficient catalyst was prepared by loading CoMn₂O₄ spinel oxide (CMO) on halloysite (HNT), a natural mineral nanotube, for the activation of peroxymonosulfate (PMS) towards the degradation of some frequently detected pharmaceuticals in water bodies. The CMO nanoparticles are evenly distributed on the outer surface of HNT tubes with little agglomeration and smaller grain size compared to bare CMO. A moderate loading of 40% CMO on HNT (i.e. 40-CMO/HNT) displayed an excellent catalytic ability, leading to the complete degradation of carbamazepine in 20 min. Carbamazepine was decomposed gradually by oxidation, hydrolysis and the cleavage of rings with 60% mineralization rate. The adhering of CMO on HNT contributed to better stability and durability than bare CMO and the recycling of 40-CMO/HNT was found feasible and efficient. A test of three-(3)-time-reuse showed that over 90% of carbamazepine was removed in each cycle, while the leaching of Co and Mn was reduced stepwise by 12.6% and 8.9%, respectively. The possible universal application of 40-CMO/HNT in removing common antibiotics was verified by targeting tetracycline, ofloxacin and sulfamethoxazole. The positive results promise the development of an effective treatment technology for the removal of common pharmaceuticals.