Degradation of dihydroxybenzophenone through monopersulfate activation over nanostructured cobalt ferrites with various morphologies: A comparative study

Abstract

Differences in the structural morphology of heterogeneous catalysts, oxygen vacancy (OV), and lattice defect degree could induce different catalytic performances due to the possession of different active sites and abundance of unpaired electrons. Despite this, few studies on in-depth discussion and detailed comparison of the influence of these factors for activating monopersulfate (MPS) have been made so far. Here, we proposed three types of nanostructured cobalt ferrites (NCFs), consisting of CoFe2O4 nanobundle (CFNB), CoFe2O4 nanosheet (CFNS), and CoFe2O4 nanoplate (CFNP). The catalytic performance of these NCFs was evaluated through MPS activation for degradation of 4,4′-dihydroxybenzophenone (DBP), an extensively used UV filter. As a result, pH-dependent generation of reactive oxygen species (ROS) showed that the catalytic mechanism tended to shift from radical and non-radial pathways under neutral conditions to 1O2-induced non-radical at low and high pH with increased generation of SO4•− and •OH. Given the abundance of OV, lattice defects, and highest specific area, CFNS possessed the most superior performance driven by high reactivity of ≡CoII/≡CoIII and ≡FeII/≡FeIII redox cycles, while DBP-induced electron transfer accounted for enhanced activity of CFNB. CFNP with relatively high OV and electrochemically active surface area, on the other hand, showed its efficiency in generation of ROS. Intermediates from the reaction were also verified through LCQ-LC/MS spectra and DFT calculation for elucidating the DBP degradation over NCFs-activated MPS.