Electrochemistry-enhanced peroxymonosulfate activation by CoAl-LDH@biochar for simultaneous treatment of heavy metals and PAHs

Abstract

An EC/CoAl-LDH@biochar/PMS system is proposed in this study for activation of PMS and removal of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs). In this system, over 90% of HMs and PAHs could be effectively removed after 40 min. Compared to other systems, the synergy between CoAl-LDH@biocahr and electrochemistry (EC)-peroxymonosulfate (PMS) had an excellent ability to eliminate the combined pollutants. The precise effect of the experimental parameters, including pH, CoAl-LDH@biochar dose, current density, and PMS concentration, on HMs-PAHs removal was determined, and the system was found to have a broad working pH range. The presence of EC can overcome the inhibition of anions in the degradation of PAHs due to the direct oxidation of PMS and PAHs on the cathode. The scavenging tests confirmed that the free radical and non-radical processes contributed to the degradation of PAHs. It is also revealed that EC can promote the continuous circulation of transition metals, which enhances the activation of PMS. The adsorption on the surface of CoAl-LDH@biochar and electrochemical deposition were the two main mechanisms for HMs removal. Furthermore, the electrode and CoAl-LDH@biochar possessed favorable recyclability in five consecutive cycles. This study has provided a promising and cost-effective approach for treatment of HM-PAH co-contaminated wastewater.