Development of a process for removing selenium from industrial water effluents generated by the hydrometallurgical recycling of metals
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- Selenium (Se) is a trace element commonly released into the effluents of hydromet allurgical recycling plants, where its bioaccumulation in aquatic ecosystems raises growing environmental and regulatory concerns. The present work was carried out at Hydrometal Belgium (Engis site), and focuses on the final wastewater stream of one particular process, which typically contains 2 to 10 mg/L of dissolved se lenium. The main objective was to develop a chemical treatment able to reduce this concentration to approximately 1 mg/L, at the lowest possible cost and using the existing installations of the Engis site. The proposed method is based on the precipitation of copper selenide (Cu2Se) by cementation, using zinc powder as the reducing agent and Cu2+ ions as the precipitating agent. At laboratory scale (5 L experiment) and under optimised parameters, the developed process reached a final Se concentration of about 0.53 mg/L starting from an Se-enriched effluent at 11.66 mg/L. A 50 L pilot-scale test was subsequently carried out to identify the main practical constraints associated with the scale-up, in particular regarding the filterability of the Zn precipitation step and the washing of the recovered cakes.