An overview study of chlorination reactions applied to the primary extraction and recycling of metals and to the synthesis of new reagents

Energy intensive classical metallurgical processes, the depletion of high-grade ores and primary sources push the scientific and technical communities to treat lean and complex ores as well as secondary metal resources for the recovery of valuable metals. Chlorination technique could be a suitable technology for this purpose. This paper summarizes laboratory experimentation of chlorination processes developed for the extraction of tantalum and niobium from their bearing materials, the upgrading of chromite, the treatment of sulfide concentrates, and the decontamination of jarosite, as well as for the synthesis of potassium ferrate. Each investigation started by a thermodynamic study of different systems (M-O-Cl, M-S-Cl, M = metal) including the calculations of the standard free energy of chlorination reactions and phase stability diagrams of these systems. The kinetics of these chlorination reactions was studied by thermogravimetric analysis. The effects of total gas flow rate, temperature, individual reactant partial pressures, etc., on the chlorination reaction rate were investigated. Besides, experiments were also conducted in tubular furnaces. Several different qualitative and quantitative analyses methods were used to evaluate the selectivity and performance of the chlorination processes. The results reported in this paper show the advantages of the chlorination technology in terms of energy saving, selectivity of the processes, and recovery rate of valuable metals. They also demonstrate the possibility to treat lean raw materials, to improve the decontamination of wastes, to generate environmentally safer residues, to engineer new compounds, etc.