Efficient catalytic degradation of MCPA using Co@MOF-808(C)/PMS: Parameter optimization and degradation path analysis

The herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) poses a significant threat to aquatic organisms and human health due to its resistant biodegradability. It is urgent to develop efficient removal methods for MCPA, especially advanced oxidation technologies based on metal organic frameworks (MOFs) catalysts. This study aims to remove MCPA by catalyzing peroxymonosulfate (PMS) with Co@MOF-808(C) and optimizing the catalytic degradation conditions with the Central Composite Design (CCD) of Response Surface Methodology (RSM). In addition, the reusability of Co@MOF-808(C) and the mineralization effect of MCPA, along with the potential degradation pathway of MCPA and the ecotoxicity of the degradation intermediates, were investigated. Results revealed that temperature, catalyst concentration, and PMS had significant impacts on MCPA degradation, and the optimal conditions were Co@MOF-808(C) 625 mg·L⁻¹, PMS 5.85 mM, pH 4.0, 45 ℃ and rotate speed 236 rpm. The total organic carbon removal efficiency of 85.9% and MCPA degradation rate of 98.1% were oobtained under the optimal conditions, and the degradation rate remained as high as 94.4% when the catalyst was reused five times. The contribution rate of reactive oxygen species (ROS) for MCPA degradation was SO 4 · − (77.8%) > ·OH (18.5%) > O 2 · − (3.7%), and the degradation pathways included decarboxylation, hydroxylation and ring opening. Moreover, the ecotoxicity of MCPA was significantly reduced after the degradation by Co@MOF-808(C)/PMS system. In consequence, the Co@MOF-808(C)/PMS process may be an efficient alternative for treating MCPA wastewater.