Simultaneous recovery of valuable metals W, Co, Ta, and Nb from tungsten leaching residue by sodium-based slag refining

Abstract

As a hazardous solid waste in the tungsten (W) materials industry, the utilization of W leaching residue (W-residue) has become a challenge. In this study, we propose a sustainable strategy for the simultaneous extraction of valuable elements W, Ta, Nb, and Co from W-residue by a sodium-based slag refining. The slag system was designed to provide a slag-liquid phase to facilitate the mass transfer and reduction reaction of the valuable metallic compounds during the refining process. The characteristics of Na2O-SiO2-NaF slag system, including the liquidus temperature and viscosity, were predicted using FactSage thermodynamics software and evaluated experimentally. Using 0.5Na2O-0.3SiO2-0.1NaF slag, the recovery efficiency of the valuable elements from W-residue can reach 94%(W), 66%(Co), 53%(Ta), and 77%(Nb), and a total recovery rate was reached 75%. The mechanism illustrated that the valuable elements (W, Co, Ta, and Nb) in W-residue can be transformed to (W, Ta, Nb, Ti)C and (Fe, Co)Si, which co-precipitated as alloy phases during the slag refining process. The present work offers a strategy, not merely limited to waste utilization of W-residue, to supplement the recycling route of W materials industry.