CoAl-Layered Double Hydroxide Catalytic Membrane for Activation of Peroxymonosulfate Towards Efficient Degradation of Organic Pollutants

In order to catalytically degrade organic pollutants, a CoAl-layered double hydroxide catalytic membrane (CoAl-LDH-M) was fabricated for the activation of peroxymonosulfate (PMS). Notably, at the dosage of 50 mg/L PMS and flow rate of 1.0 mL/min, 99.7% removal of Rhodamine B (RhB) was obtained. The corresponding removal efficiency of total organic carbon (TOC) was 59.9%. This demonstrated that CoAl-LDH-M possessed high efficiency for PMS activation. Inductively coupled plasma (ICP) results showed that the leached amount of cobalt and aluminum were 0.13 and 0.04 mg/L, indicating the high stability of CoAl-LDH-M. The CoAl-LDH-M /PMS system could also effectively degrade several other contaminants, obtaining removal efficiencies of 92.7-99.6%. The effects of pH and co-existing ions were investigated as well. Reusability of the catalytic membrane was evaluated in both distilled water and synthetic wastewater. Mechanism studies showed that both reactive oxidative species (ROSs) and non-radical electron transfer were involved. The non-radical electron transfer played the primary role. The degradation pathway of RhB was unraveled by liquid chromatography-mass spectrometry measurements and theoretical calculations. Furthermore, the ecotoxicity of the reaction intermediates was evaluated by utilizing quantitative structure activity relationship (QSAR) calculations.