Effective utilization of bromine in seawater: Application to water purification technique with supplying ozone minute-bubbles

摘要

To create the comprehensive utilization system of seawater resources based on the salt production process,the utilization method of dissolved bromine(Br)in the discharge concentrated brine of salt manufactory in Japan was developed.In the existence process,Br is recovered by a blowout method with Cl2 gas bubbling from the removed K+ bittern as the liquid Br2,which is used to the chemical reagents in fine chemical field so as the catalyst,medicinal drug,inorganic material and pesticide.On the other hand,the oxidation products of Br has the various forms so as the hypobromous acid(HBrO),bromous acid(HBrO2)and bromic acid(HBrO3),and it's application for the water purification process can be expected.For example,HBrO has a highest oxidation potential for the organic compounds,is obtainable by the ozone(O3)oxidation reaction of dissolved Br in aqueous solution. In this paper,when ozone/oxygen(O3/O2)minute-bubbles were supplied to seawater or NaBr,the influences of the dissolved each salt on the generation of oxygen species(OS)were investigated.The concentration of oxygen species in aqueous solution was determined by colorimetric method.As the results,the solution concentration of total oxygen species(C_(OS))in modified seawater or 1.0 mmol/l NaBr solution during the supplying O3/O2 minute-bubbles was increased approximately 1.3-times compared with ion-exchanged water at a reaction time of 120 min.Additionally,when the O3/O2 minute-bubbles were supplied into 5.0 mmol/l methylene blue(MB)solution,the initial decomposition rate of MB was increased approximately 1.2 times by adding NaBr with concentration of 1.0 mmol/l.Consequently,it seems that the improvement of the organic compound decomposition was induced by presence of Br ion during O3/O2 minute-bubble supply.