Effect of quenchers on the electrochemical oxidation of phenol in presence of electro-generated active chlorine

Abstract

According to the literature, the treatment of water and wastewater by electro-generated active chlorine is a very promising method from an applicative point of view. However, the production of toxic organic and inorganic chlorinated by-products, occurring during the oxidation of organic compounds by electro-generated active chlorine, must be carefully minimized to accomplish law constraints. If organic species could be oxidized, inorganic ones are persistent and difficult to be removed. Thus, it is necessary to avoid or minimize their production. Here, the use of quenchers able to react with active chlorine was investigated in the frame of the electrolysis of solutions of phenol and chlorides at BDD anodes in order to systematically evaluate the effect of various operative conditions (nature and concentration of the quencher, addition at different times, production in-situ) both on the degradation of organics and on the formation of by-products. In particular, for the first time, the analysis of several by-products was provided (both organic, such as chloroacetic acids, chlorophenols and carboxylic acids, and inorganic, as active chlorine, ClO2, chlorate and perchlorate) in the presence of quenchers. It was found that the use of a quencher under suitable operative conditions results in a relevant reduction of the concentration of various by-products, including chlorate, without reducing the removal of TOC.