Electrochemical degradation of dissolved organic matters in oil sands process water using continuous-flow packed bed electrode reactor

Abstract

In this study, a continuous-flow packed bed electrode reactor (PBER) was presented for the first time to reclaim oil sands process water (OSPW) generated during the bitumen extraction of oil sands surface mining. The PBER was constructed based on a traditional two-dimensional electrode system (2-DES) by packing pretreated spherical activated carbon (SAC) between the anode and cathode, forming the third electrode, charged and polarized under the electric field. The electrochemical treatment effect of three essential control factors, including cell voltage, electrode space, and flow rate, were investigated on the degradation of dissolved organic matters (DOMs) in OSPW. Electrolysis for 180 min under obtained optimal conditions: cell voltage 10 V, electrode space 6 cm and flow rate 5 mL/min, achieved 74.49% COD and 65.85% DOC removal percentage in PBER compared with only 11.72% and 12.97% achieved in 2-DES at similar conditions. The energy consumption and current efficiency were also significantly improved from 12.29 to 2.21 kW·h/g COD and 9.81% to 54.59%, respectively, thanks to the application of the third electrode. Further analysis revealed that the naphthenic acids (NAs), the primary source of acute toxicity in OSPW, were effectively degraded during PBER electrolysis, which was also validated by the Microtox® test that showed no acute toxicity in the PBER-treated OSPW, indicating that PBER could significantly improve the OSPW's biodegradability. This study first demonstrated that PBER was a prospective technology for process water recycling in oil sands production and tailings ponds reclamation, particularly compared to the traditional 2-DES electrolysis.