Experimental Study On The Kinetics Of Ultrasonically Enhanced Leaching Of Germanium From Oxidized Roasting Slag

Scattered metal germanium is a kind of high-tech material with many characteristics and strategic position,which plays an extremely important role in economic development and science and technology.Hard zinc residue is one of the important materials in enrichment and extraction of germanium.At present,germanium production enterprises main technological process of recovering germanium from the hard zinc residue usually is as follows,1)the vacuum distillation,2)the neutral leaching,3)the oxidizing roasting,4)the chlorination distillation and 5)the hydrolysis."Chlorination distillation"is an essential step in the process of extracting germanium,while there are many problems during the process of chlorination distillation,such as the high acidity,low leaching rate of germanium,equipment corrosion and some security issues.In order to solve the above process defects,the leaching experiment of germanium in HCl-CaCl₂ system and the dynamical study of leaching germanium by ultrasonic-assisted leaching were researched,the oxide roasting slag prepared by a company in Yunnan was used as raw materials.Calcium chloride was added to increase the concentration of chloride ion and the activity of hydrochloric acid,thus reducing the concentration of hydrochloric acid and the oxidation-reduction potential of metal,and promoting the formation of GeCl₄by the coordination of germanium ions with chlorine ions.The following conclusions were obtained by conventional leaching experiments and ultrasonic-assisted leaching dynamical experiments:（1）Influence factor about germanium in oxidizing roasting slag in HCl-CaCl₂system research by orthogonal experiment in conventional leaching experiments.The research indicates that the optimum leaching rate of germanium about conventional leaching is obtained at temperature 75℃for a leaching duration of 90 min need5.5mol/L the concentration of initial hydrochloric acid,100g/L the concentration of calcium chloride and the ratio of liquid to solid is 7:1.The verification research indicates that the optimum leaching rate of germanium 89.56%about conventional leaching and this discovery is consistent with the results of the orthogonal test.The arrangement of the influence is:the concentration of initial hydrochloric acid,the ratio of liquid to solid,the leaching temperature,the concentration of calcium chloride and the leaching time.（2）The preliminary study results of ultrasonic-assisted leaching experiments showed that the leaching rate of germanium by ultrasonic-assisted leaching was92.7%,under the optimal leaching conditions:leaching temperature 80°C,the concentration of initial hydrochloric acid 3.5mol/L,the concentration of calcium chloride 150g/L,leaching time 40min,the ratio of liquid-solid is 8:1,ultrasonic power700W.Compared the ultrasonic-assisted leaching experiment with the conventional leaching experiment,it can be found that under the optimum leaching conditions,the reaction time is shortened by 56%,the initial hydrochloric acid concentration is decreased by 36%,and the leaching rate of germanium is increased by 3%.This is mainly due to the ultrasonic material can break the material,open the inclusion,so that the particle size of the filter residue is smaller and dispersed evenly,the surface is loose and void.At the same time,the grain growth is hindered,the reaction of germanium and hydrochloric acid is promoted,the mass transfer process is accelerated and the leaching reaction is enhanced.Therefore,the new process has the advantages of reducing acid consumption,improving leaching rate,improving reaction conditions and green safety.（3）The study about dynamic experimental of ultrasonic wave enhanced leaching of germanium in roasted slag was carried out.The research proved that ultrasonic wave method can greatly shorten the reaction time and raise the leaching rate of germanium in oxidizing roasting slag at the larger the liquid-solid ratio,increasing leaching temperature,increasing the initial concentration of hydrochloric acid,calcium chloride concentration and the increase of ultrasonic power.The apparent activation energy of leaching process is 8.245kJ/mol,controlled by diffusion and belongs to the unreacted core model.which is 12.823kJ/mol lower than the apparent activation energy of conventional leaching.Meanwhile,the activation energy is close to the lower limit of the activation energy for diffusion control（8kJ/mol）,which indicates that the introduction of ultrasound greatly improves the chemical reaction environment and minimization of the barrier needed to span the diffusion control,thus effectively enhancing the leaching reaction.