Recovery of rhenium and tungsten from calcium tungstate containing rhenium via hydrochloric acid decomposition

In view of calcium tungstate containing rhenium generated during the recovery process of tungsten-rhenium alloy waste, rhenium and tungsten were separated by hydrochloric acid decomposition, followed by ion exchange enrichment and evaporation crystallization for rhenium recovery; then, tungsten was recovered by calcining the obtained tungstic acid. The results showed that the leaching efficiency of Re reached 99.76% for HCl concentration of 2.7 mol/L, liquid-to-solid ratio of 26:1, temperature of 80 degrees C, and time of 5 h. The Re mass percentage in tungstic acid product decreased to 0.0005%. After adsorbed by A170 resin and desorbed by 10% ammonium hydroxide, the Re concentration of the leaching solution was enriched from 176.50 mg/L to 4.61 g/L with the enrichment ratio of 26.12; the adsorption and desorption ratios of Re were 80.83% and 96.94%, respectively. The SEM morphology of NH4ReO4 crystals crystallized from the enriched solution was dendritic. The decomposition reaction conforms to shrinking core model, and the activation energy was calculated as 53.46 kJ/mol with internal diffusion and chemical reaction as the rate-controlling step. The submicron spherical-like tungsten trioxide, with average particle size of 195.53 nm-540.10 nm, was obtained by calcining the tungstic acid at 900 degrees C and air atmosphere for 0.5 h-5 h.