The electrochemical treatment of brackish and seawaters with boron doped diamond anodes (BDD) can be particularly suitable for the removal of microorganisms, microalgae and pollutants: the high conductivity of these waters and the high content of chloride ions can be exploited in disinfection/oxidation processes mediated by active chlorine. A correct choice of operating conditions can limit the formation of such undesired by-products as bromate and chlorate ions. RESULTS: Galvanostatic electrolyses of synthetic waters containing chloride and/or bromide ions using BDD anode were carried out both in batch and continuous mode in an undivided cell. Bromide ions were oxidized to form bromate ions with high conversion rate, while chlorate ions were found as by-products of the oxidation of chloride ions together with active chlorine. When solutions containing Br- and Cl- were treated, the increase in the concentration of chloride up to that of seawater (20 g dm-3), hinders the formation of BrO3 - and ClO3 -. CONCLUSIONS: The electrochemical process with BDD anode could be applicable to the disinfection of high salinity waters: in synthetic solution simulating the composition of seawaters, high amounts of active chlorine are formed and the occurrence of bromates and chlorates is highly limited.
On the formation of bromate and chlorate ions during electrolysis with boron doped diamond anode for seawater treatment
VACCA, ANNALISA;MASCIA, MICHELE;PALMAS, SIMONETTA;MAIS, LAURA;RIZZARDINI, SIMONE
2013-01-01
Abstract
The electrochemical treatment of brackish and seawaters with boron doped diamond anodes (BDD) can be particularly suitable for the removal of microorganisms, microalgae and pollutants: the high conductivity of these waters and the high content of chloride ions can be exploited in disinfection/oxidation processes mediated by active chlorine. A correct choice of operating conditions can limit the formation of such undesired by-products as bromate and chlorate ions. RESULTS: Galvanostatic electrolyses of synthetic waters containing chloride and/or bromide ions using BDD anode were carried out both in batch and continuous mode in an undivided cell. Bromide ions were oxidized to form bromate ions with high conversion rate, while chlorate ions were found as by-products of the oxidation of chloride ions together with active chlorine. When solutions containing Br- and Cl- were treated, the increase in the concentration of chloride up to that of seawater (20 g dm-3), hinders the formation of BrO3 - and ClO3 -. CONCLUSIONS: The electrochemical process with BDD anode could be applicable to the disinfection of high salinity waters: in synthetic solution simulating the composition of seawaters, high amounts of active chlorine are formed and the occurrence of bromates and chlorates is highly limited.
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