Dual role of halloysite nanotubes in the synthesis of the complex with CoAl2O4 and tetracycline degradation

Halloysite nanotubes (HNTs) served as the support and aluminum source for in-situ synthesizing CoAl 2 O 4 /HNTs (CAO/HNTs), which acted as an effective catalyst to activate peroxymonosulfate (PMS) for degrading tetracycline hydrochloride (TC). To achieve the optimal removal performance, various parameters were optimized. The final CAO/HNTs demonstrated a high degradation efficiency of 88 % toward TC within 40 min, which was 1.69 times as high as that of pure CAO. The existence of HNTs made CAO highly dispersed, increasing the number of exposed active sites and the contact opportunities between CAO and TC molecules, which enabled CAO to participate in the reaction more effectively and thus improved the degradation efficiency. Additionally, the formation of Co-O-Al bonds facilitated the growth of CAO into a three-dimensional (3D) spherical structure with more active sites other than the tetrahedral structure on HNTs. In the CAO/HNTs/PMS system, O 2 •– and 1 O 2 contributed mostly to the catalytic process. This work not only provides a novel catalyst for the treatment of antibiotic pollution, but also offers an innovative strategy for fabricating functional materials on the basis of chemical composition and morphology characteristics of natural minerals.