Electrochemical treatment of wastewater containing NaCl. Methods to increase the removal of organic pollutants and minimize the formation of toxic by-products

In many cases, wastewater can contain both organic pollutants and NaCl. Electrochemical methods allow to treat very effectively organic pollutants in the presence of NaCl. However, the utilization on an applicative scale of this route is limited by the fact that usually the high removals of organics is coupled with the generation of significant amounts of chlorinated by-products. The role of several operative parameters on the performances of the process was systematically evaluated using phenol as a model organic pollutant. It was shown that the removal of phenol and TOC and the generation of many by-products including chlorophenols, chloroacetic acids, chlorate and perchlorate dramatically depend on the adopted operative conditions (i.e., nature of anode and cathode, current density and concentration of chlorides). The use of boron doped diamond anode gave the highest removal of TOC but also the highest final concentrations of chlorate and perchlorate and the lowest concentrations of chloroacetic acids. Conversely, the use of DSA anodes gave the lowest generation of chlorate and no perchlorate. The use of lower current densities and higher air pressures allowed as well to reduce the concentrations of these compounds. Moreover, lower amounts of chlorinated by-products were achieved using suitable cathodes [1]. References [1] Hao, Y., Ma, H., Proietto, F., Galia, A., Scialdone, O. 2022, Electrochim. Acta, 402,139480.