Electrochemical Oxidation of Bromides on DSA/RuO2 Anode in the Semi-Industrial Batch Reactor for On-Site Water Disinfection

Abstract

The electrochemical oxidation of bromides for on-site water disinfection, on dimensionally stable DSA titanium coated RuO2 anode is investigated by the polarization measurements and in the semi-industrial batch reactor under constant current conditions. During electrolysis of 0.4 M bromide with the current of 5 A, the concentration of bromine, Br-2, tribromide ions, Br-3(-), hypobromous acid, HOBr, and hypobromite, BrO-, so-called equivalent bromine, Br-eq, is determined using arsenometric titration at pH similar to 9 and pH similar to 3.5. At pH similar to 9, the concentration of 0.1 M is obtained, but solutions undergo to fast decomposition. In the acidified electrolyte, the stable bromine solution with the concentration of 0.15 M after 1.75 h of electrolysis is obtained, corresponding to 14 g dm(-3) of "active bromine", a mixture of HOBr and OBr-. With typical dosing rate of active bromine for disinfection of similar to 0.5 mg per liter of water, it is suggested that investigated batch semi-industrial reactor can be used for the treatment of similar to 28.000 liters of water. Basic electrolysis parameters like, reactor voltage, temperature, pH, current efficiency, energy consumption is also determined. The reaction products are determined using thermodynamic equilibrium consideration and UV-vis spectroscopy measurements. The main loss reaction during electrolysis is considered, and appropriate analytical expressions are suggested.