Effect of high salt concentrations on ozone decomposition in water

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Abstract
Ozone decomposition in water in the presence of different salts has been studied. The stability of ozone varies depending on the salt nature and the pH. At low pH, molecular phosphoric acid has a positive influence upon ozone conversion. At neutral and basic pH, ozone decomposes through a radical mechanism, whose termination step depends on the type of ionic species present. So, at pH 6 in the absence of salts or in the presence of chloride ions it is proposed a second order termination step. In addition, the direct reaction between ozone and chloride ion has to be considered. When there are sulphate, phosphate or carbonate ions present in the water, the termination step changes to first order due to the hydroxyl radical scavenging effect of these ions. Hence, these ions estabilize molecular ozone in water.