CoM/diatomite (M = Mg and Al) for the activation of peroxymonosulfate to degrade atrazine in water: Effect of preparation method, role of acidic/basic sites, and catalytic mechanism

Abstract

A cost-effective and eco-friendly catalyst is desirable for activating peroxymonosulfate (PMS) into reactive oxygen species (ROS) to abate organic pollutants in water. It is the first-ever research to synthesize a highly efficient PMS-activator by incorporating cobalt on as-synthesized Mg- and Al-loaded diatomite (DM) by impregnation (IM) and precipitation-deposition (PD) methods. The catalysts showed a mixture of the plate and pinnate-like morphologies. Atrazine (ATZ) degradation by diatomite-based catalysts followed the order of Co6Mg10/DM-IM > Co6Mg10/DM-PD > Co6Al10/DM-IM > Co6Al10/DM-PD. ATZ removal by sole PMS and adsorption was negligible. The Co6Mg10/DM-IM morphology, structure, and catalytic activity were well-maintained after reuse, with minor Co (0.05 mg L−1) and Mg (3.05 mg L−1) leaching. The ROS (OH, SO4−, O2− and 1O2) were generated due to redox couples [Co2+/Co3+, and O2−/O2] and decomposition of PMS. Improved catalytic efficiency was ascribed to the Co/Mg and Co/Al synergism, spatially interconnected architecture with lower charge-transfer resistance, open porous structure, diffusion-friendly channels, abundant OH groups, and ROS generation. This research provides an insight into how tuning the surface chemistry of DM in terms of acidity and basicity can enhance the catalytic activity of other transition metals (such Fe, Mn, Cu, and their composites) for AOPs.