Electrochemical denitrificacion with chlorides using DSA and BDD anodes

In this work, the electrochemical denitrification of solutions containing chlorides is studied with two different types of anode materials: O2-dimensionally stable anodes (DSA) and boron doped diamond (BDD). First of all, a higher rate of nitrate removal was found when chloride is used as the supporting media, with respect to sulphate. Moreover, it was found that it is necessary a minimum chloride concentration to get an effective treatment and that gaseous-nitrogen is the primary nitrogen species found in the electrolyses. In this process, nitrate is firstly reduced on the cathode surface and next oxidized by the species generated by the anode material. Thus, anode material does not influence on the denitrificacion rate, but it significantly influences on the speciation of chlorine. Furthermore, formation of perchlorates advice against the use of BDD electrochemical denitrification for the production of drinking water. Finally, formation of chlorates in the DSA-electrolyses, due to the ageing of hypochlorite, also limits its use in the production of drinking water, although it does not exclude its use in other applications such as reuse of treated wastewater and treatment of industrial wastes.

Figure optionsDownload as PowerPoint slideHighlights
► Electrolyses of nitrate in the presence of chloride lead to the formation of gaseous-nitrogen species.
► Very important role of the anode material in the speciation of chloride.
► Key influence of chloride concentration in the rate of nitrogen removal.
► Formation of perchlorates and chlorates when using BDD electrode, which may advice against the use of this electrode in the production of drinking water.