The solid dihydrate and hexahydrate can be obtained by evaporation. Preparation Ĭobalt chloride can be prepared in aqueous solution from cobalt(II) hydroxide or cobalt(II) carbonate and hydrochloric acid: The octahedron is completed by a pair of mutually trans aquo ligands. Each Co center is coordinated to four doubly bridging chloride ligands. The dihydrate, CoCl 2(H 2O) 2, is a coordination polymer. The anhydrous salt is hygroscopic and the hexahydrate is deliquescent. This species dissolves readily in water and alcohol. The crystal unit of the solid hexahydrate CoClĢO contains the neutral molecule trans- CoClĤ and two molecules of water of crystallization. Concentrated solutions are red at room temperature but become blue at higher temperatures. Under atmospheric pressure, the mass concentration of a saturated solution of CoClĢ in water is about 54% at the boiling point, 120.2 ☌ 48% at 51.25 ☌ 35% at 25 ☌ 33% at 0 ☌ and 29% at −27.8 ☌. Solutions Ĭobalt chloride is fairly soluble in water. The vapor pressure has been reported as 7.6 mmHg at the melting point. At about 706 ☌ (20 degrees below the melting point), the coordination is believed to change to tetrahedral. 64–70.At room temperature, anhydrous cobalt chloride has the cadmium chloride structure ( CdClĢ) (R 3m) in which the cobalt(II) ions are octahedrally coordinated. Chen, Hunan Nonferrous Metals, 2014, vol. Gerven, Journal of Sustainable Metallurgy, 2015, vol. Forsberg, Journal of Sustainable Metallurgy, 2018, vol. Furthermore, this is a promising technique for separating and extracting nonferrous metals from iron-based sulfide materials. The temperature-programmed NH 4Cl roasting–water-leaching process considerably improves the selective sulfation of the nonferrous metals.
The chlorides of Ni, Co, and Cu were successfully transformed into sulfates. The results indicate that sulfide chlorination occurred because of the NH 4Cl additive and the formed intermediates, including metal chlorides and chlorine gas. The phase evolution as well as the chlorination and sulfation mechanisms during the three-step roasting process were examined by the roasting–leaching experiments and the X-ray diffraction, energy-dispersive X-ray spectroscopy, and thermodynamic calculations. The results suggest that the water-leaching yields of Ni, Co, and Cu reached ~ 97, ~ 95, and ~ 99 pct, respectively, whereas that of iron was ~ 1 pct under the following optimized conditions: the first roasting step temperature was 250 ☌, the heating rate was 2 ☌/min, the dosage of the NH 4Cl additive was 80 mg/g (ore), the holding times at 250 ☌ and 650 ☌ were 120 and 60 minutes, respectively, and the particle size of the NH 4Cl additive was smaller than 75 μm. The dosage of NH 4Cl was drastically reduced, and chlorine-free calcine was obtained using a chlorination–sulfation roasting schedule. During the roasting process, several vital parameters were investigated to achieve the high co-sulfation of Ni, Co, and Cu. In this study, we propose a novel temperature-programmed ammonium chloride (NH 4Cl) roasting–water-leaching process to extract nickel (Ni), cobalt (Co), and copper (Cu) from polymetallic sulfide minerals in a synchronous, efficient, and environment-friendly manner.
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