Leaching process of germanium oxide dust

A thermodynamic analysis on the acid leaching process of germanium oxide dust and discussion on the behaviors of main substances of the dust in the leaching process were carried out. The effects of temperature, acid concentration, leaching time and stirring speed on the leaching rate of germanium were investigated. Based on the characteristic of the dust, the kinetics and reactive mechanism of acid leaching were stud- ied. The results show that the leaching of the dust by acid belonged to "the unreacted core shrinking model" of producing solid outgrowth layer. The chemical reaction was controlled by inner diffusion process. The apparent activation energy of leaching process was 12.60 kJ/mol. The leaching reaction of germanium was determined to be mainly second order reaction. The optimum conditions were the reaction tem- perature of 363 K, the leaching time of 2.5 h, the stirring speed of 120 r/min, the solid-to-liquid ratio of 1/8 and the acid concentration of 120 g/L. Under these conditions, the leaching rate of germanium can come up to more than 87%.