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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.

Textile waste water containing dyes, surfactants, salts and other contaminants represent a challenge for the selection and design of treatment processes due to the stability of some of its components. Advanced oxidation processes (AOPs) are attractive alternatives to partially or totally degrade dyes and other persistent pollutants using relatively compact devices to perform water treatment. To test the efficiency of these technologies it is necessary to count with laboratory made solutions that can match the characteristics of a typical textile waste waters effluent. In this work the application of two AOP, ozonation and photo-Fenton, to the treatment of textile effluents are compared, using a specially design model solution. The effect of typical textile wastewater composition on the treatment efficiency is discussed. Higher decoloration efficiencies were obtained with both AOPs tested in this work, being slightly higher with ozonation. TOC was only partially removed, being more efficient photo-Fenton than ozonation.