Effective removal of silica and sulfide from oil sands thermal in-situ produced water by electrocoagulation

Abstract

Effective removal of silica and sulfide from oil sands thermal in-situ produced water can reduce corrosion and scaling of steam generators, enhancing water recycling and reuse in the industry. The removal of these two solutes as well as calcium and magnesium (i.e., the solutes that can also cause scaling) from synthetic and authentic produced waters by electrocoagulation (EC) was investigated in this study. In Fe0-EC, the precipitation of FeS minerals resulted in a rapid removal of sulfide and adsorption of silica onto FeS. In Al0-EC, silica was removed via adsorption onto aluminum hydroxides, but sulfide was poorly removed. In both EC systems, Ca2+ and Mg2+ were removed from the organic-free synthetic produced water but not from the authentic water, likely due to the influence of organic species. Contaminant removals in Fe0-EC were controlled by charge density (q, C/L) but not current density (i, mA/cm2). Overall, this research suggests that EC can be a promising technology for the treatment of thermal in-situ produced water. Fe0-EC appears to be a better choice than Al0-EC considering that Fe0-EC was more effective at removing sulfide, and that Fe0 anodes are usually less expensive.