Selective Removal of Refractory Metals from Effluents by Liquid Ion Exchange Based Technologies

摘要

Refractory metals are often appearing as couples or multi-component mixtures in aqueous solutions. These solutions may be generated from the treatment of primary sources (Mo-Re, Ta-Nb, Zr-Hf) or from recycling activities such as hydrometallurgical reclamation of spent catalysts [Mo-V, Mo-W, Mo-Re] or super alloys (Mo-Re, W-Re, V-Mo). Many of these elements show complex chemical behaviour in aqueous solutions and, due to their similar chemical properties, are difficult to separate by conventional chemistry. Solvent extraction is now widely used as a tool for the separation and concentration of these metals. However, for the treatment of effluents or product solutions with low concentration of the metals of interest, the use of huge volumes of solvent is not always recommended and technologies taking advantage of the powerful separation characteristics of liquid ion exchangers (or mixtures of them) but with low solvent inventory have been developed. To these technologies belong Supported Liquid Membranes (SLM) and Solvent Impregnated Resins (SIR). In this paper we will focus on Rhenium recovery and results are presented concerning the treatment of a Re-Mo flue gas effluent by the liquid ion exchange based technologies SLM and SIR. It is shown that it is possible to separate Re from Mo efficiently by SLM and SIR. From an effluent initially containing 1.133 g/1 Re and 3.475 g/1 Mo, a concentrated pure NH_4ReO_4 solution can be generated by SLM with a content of 14.3 g/1 of Re, enabling efficient down stream processing to isolate pure ammoniumperrhenate. It is also shown that SIR have a similar potential to separate both metals.