Comparing the precipitation techniques on rhodium recovery from waste solutions

Experimental study performed in this research aimed at precipitating various rhodium compounds from the spent solutions of rhodium plating. Optimum conditions for the rhodium hydroxide precipitation, corresponding to a final Rh³⁺ concentration of 50 ppm, were found to be pH=7.5, 50°C temperature, and 6 hours of reaction period, when NaOH is used as a neutralizer. Characterization studies were also carried out to inspect the suitability of precipitated rhodium compounds for the manufacturing of pure metallic rhodium and rhodium salts. Optimum conditions for rhodium precipitation are 180 g/l sodium formate concentration, 100 °C temperature and over 6 hours time. Sodium formate precipitation of rhodium has been carried out with an efficiency of higher than 75%.