Development of an Electrochemical Process for the Simultaneous Treatment of Wastewater and the Conversion of Carbon Dioxide to Higher Value Products

Many researchers have shown that selected anodic processes allow effective treatment of a very large amount of wastewater contaminated by pollutants resistant to biological processes. In the meantime, various authors have also shown that carbon dioxide can be converted into higher value products, such as formic acid or synthesis gas, by cathodic reduction at suitable cathodes. These two processes present interesting economic potential that, however, still needs to be improved for further development at an industrial level. Herein, these two kinds of process are combined in the same cell to improve their economic feasibility. In particular, the anodic treatment of wastewater at a boron-doped diamond anode and the cathodic reduction of carbon dioxide to formic acid at a tin cathode are performed simultaneously in a divided cell. Aqueous solutions of Acid Orange 7, which is a widely used azoic dye resistant to conventional biological processes, are used as a model for wastewater. The effect of various operating parameters (including current density, mixing rate, and pH) on both processes is studied. It is possible, under optimized operating conditions, to successfully achieve in a single reactor both the treatment of wastewater contaminated by resistant pollutants and the conversion of carbon dioxide into formic acid. This paired electrolysis process can improve substantially economic figures with respect to each separate process.