Fluidized-bed homogeneous granulation process: Comparison of individual and mixed precipitation of cobalt and copper

Abstract This research investigated the feasibility for the cobalt (Co2+) and copper (Cu2+) recovery from a synthetic wastewater by using the fluidized-bed homogeneous granulation (FBHG) process. Sodium carbonate was used as the precipitant in the operation under a continuous mode in standard atmospheric conditions. The tested parametric variables included pH, [CO32–]:[M2+] molar ratio, initial metal concentration and chloride concentration. The highest granulation and removal efficiencies of a 7.0 mM Co2+ wastewater attained 94.0% at pH 8.5% and 99.0% at pH 9.0, respectively. For a 7.0 mM Cu2+ wastewater, the highest granulation and removal efficiencies were 95.3% at pH 7.0 and more than 99.0% at pH 7.0–8.5, respectively. The best conditions for the [CO32–]:[M2+] molar ratio was at 2.0 for all cases. Most Co2+ and Cu2+ granules had formed sizes less than 0.1 mm in diameter. For the mixed metals of 10.5 mM Co2+ and 10.5 mM Cu2+ synthetic wastewater, the optimum conditions were at pH 8.5 and a [CO32–]:[M2+] molar ratio of 2.0 that yielded maximum granulation and removal efficiencies of 96.0% and 97.8% for Co2+ and 97.8% and 99.8% for Cu2+, respectively. Approximately 95.0% of the granules had the diameter size of less than 0.1 mm. In the presence of chloride, the removal and granulation efficiencies of metals and its granule size decreased significantly. This proves to show the viability of the FBHG in treating Co2+ and Cu2+ containing wastewater in industrial applications.