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, Br2, tribromide ions, Br3−, hypobromous acid, HOBr, and hypobromite, BrO−, so-called equivalent bromine, Breq, is determined using arsenometric titration at pH∼9 and pH∼3.5. At pH∼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 ∼0.5 mg per liter of water, it is suggested that investigated batch semi-industrial reactor can be used for the treatment of ∼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.