Recycling of Wastewater Containing Iron-Complex Cyanides Using UV Photodecomposition and UV Ozone Oxidation in Combination with an Ion-Exchange Resin Method

Wastewater contaminated with iron-complex cyanides was processed by UV photodecomposition accompanied by an iron elimination process using an iron-adsorbent. The wastewater processed by UV photodecomposition was oxidized by ozone combined with UV irradiation. The treated water was deionized by an ion-exchange resin method. This combined processes further increased the production of the pure water volume compared to a single process using an ion-exchange resin. The technique developed in this study can be summarized as follows. First, the iron-complex cyanides in plating wastewater were converted into aquapentacyanoferrate(III) [Fe(CN)5(H2O)]3− ion. Following the application of UV irradiation, it was decomposed into iron and cyanide (CN−) ion. The iron was removed from the water in the form of Fe(OH)3 by processing the wastewater with ozone and an iron-adsorbent. The CN− ion was oxidized to the cyanate (OCN−) form by UV ozone oxidation in a relatively short time. The processed water was de-ionized by passing through cation and anion-exchange resins. The deionized water could be reused as rinsing water in a plating process. The results reported here suggest that wastewater contaminated with chemically stable iron-complex cyanides can be effectively recycled.