Degradation of surrogate and real naphthenic acids from simulated and real oil sands process water using electrochemically activated peroxymonosulfate (EO-PMS) process

Abstract

The remediation of dissolved organics in oil sands process water (OSPW), specifically, naphthenic acids (NAs) is considered a major challenge facing the oil sands industry due to recalcitrant and persistent nature of this class of organics in the environment. Herein, the degradation of 5-Phenylvaleric Acid (PVA) as a NA surrogate compound and real NAs in a simulated OSPW and real OSPW was investigated by coupling electro-oxidation and electrochemically activated peroxymonosulfate (EO-PMS) process. The combined EO-PMS process showed high removal efficiency of PVA, in which EO was enhanced by the successful electrochemical activation of PMS at different electrode surfaces. The effects of different cathode and anode materials, initial PMS concentration, and applied current intensity on the PVA degradation were investigated. The PVA degradation efficiencies increased with the increase in the PMS concentration and applied current, however, decreased at higher levels. Carbon felt cathode and BDD anode showed the highest improvement during EO-PMS process. Both sulfate radicals (SO4•‾) and hydroxyl radicals (•OH) were found to be the primary reactive oxidants identified for the PVA degradation by both radical scavenger and spin-trapped techniques. A complete degradation of 50 mg/L PVA solution and significant reduction of the classical and oxidized NAs as well as aromatics in real OSPW were achieved by EO-PMS compared to EO alone. The results confirmed that the combination of electrochemical oxidation and electro-activated PMS process (EO-PMS) could be a promising and efficient technology for the treatment of recalcitrant NA compounds in OSPW.