Chromic acid recovery by electro-electrodialysis

Electro-electrodialysis is a promising technology for chromic acid recovery and static rinse water purification. It combines the recovery of the plating chemicals from rinse water, the elimination of metallic impurities from the process and rinse water treatment in one step. Previous industrial use was restricted due to non-resistant anion-exchange membranes and process ineffectiveness. In this work, a stable and economical process is developed and high-quality chromic acid is recovered using a new oxidative stable anion exchange membrane (AEM Fumasep® FAP, FuMA-Tech GmbH). The membrane stability and performance is evaluated by a long-term experiment for 400 h. Recovery rates were determined for batch and continuous operation and at different operation temperatures. The highest chromic acid production was reached by batch processing at 40 °C. Both measures increase significantly the chromate transfer and result in lower equipment size and operational costs.