Removal of metal ions from water using oxygen plasma.

Zinc ion dissolved in water is attempted to be removed by generating the oxides of zinc using the oxygen gas in dielectric barrier discharge (DBD) plasma system. The removal rate of zinc oxides' production (ZnO and Zn(OH)) are measured at different treatment periods by the oxygen plasma penetration in water. The removal rate of the deposit increases initially and then decreases with the treatment period. The maximum removal rate (29%) of zinc ion from water is achieved at the treatment period of 10 min, where pH is lower (7.4). From FTIR the generation properties of zinc oxide can be recognized. Initially the amount of the deposit increases with the ozone treatment period due to production of both ZnO and Zn(OH). After that, the production of Zn(OH) increases even when the total removal rate of the deposit decreases. Therefore, to remove zinc ion from water forming metal oxide deposit, the penetration amount of the active oxygens to the water must be controlled to keep the pH lower than around 7.5. Because with increasing pH amount of removal rate of zinc oxides' deposit decreases. The pH of the zinc dissolved water treated by ozone depends on both zinc ion and ozone concentration in water.