Abstract
Wastewater containing Cr3+ and organic matter from chromate(III) treatment was oxidized by ozone combined with ultraviolet (UV) radiation. The treated water containing Cr6+ after the oxidation process was purified by passing through a cation exchange resin column and then through an anion exchange resin column. This combined process increased the production of pure water volume compared to a single process using an ion exchange resin. Electric conductivity of effluent water from the anion exchange resin column was less than 20 µS/cm. This deionized water can be reused as rinsing water in the chromate(III) treatment process.
Concentrated Cr6+ discharged upon regeneration of the anion exchange resin was refined by a new ion exchange resin method which was developed in order to exclude chloride ions selectively. Cr6+ solution with high purity and low contents of chloride ion was recovered from this solution. Based on these experiments, we devised a practical recycling system by which water in toxic Cr6+ wastewater can be reused as de-ionized water on an industrial scale at a plating factory, and Cr6+ in the wastewater can be recovered as raw material for chromium products.
