Microwave Roasting Pretreatment-basic Research On Ultrasonic-assisted Leaching Of Germanium Concentrate

Germanium is a kind of high-tech materials with a variety of special properties.Lignite is a main source of extraction and recovery of germanium.At present,germanium in lignite is usually extracted by “vacuum distillation/ neutral leaching/ oxidation roasting/ chlorination distillation/ hydrolysis” in production..However,there are many disadvantages in the process of chlorination distillation,such as high concentration of hydrochloric acid,low recovery efficiency of germanium,serious corrosion for equipment and unsafe operation.In this paper,a new process for extraction of germanium from HCl solution system by microwave roasting pretreatment and ultrasonic assisted chlorination leaching was proposed.The lignite ash prepared by corporation was used as raw material and manganese dioxide was used as oxidant.The effects of microwave roasting temperature,microwave roasting time,leaching time,leaching temperature,initial concentration of hydrochloric acid,oxidant dosage and ultrasonic power on germanium leaching were studied and effect of ultrasonic assisted was analyzed.It was found leaching efficiency was improved greatly and oxidant added convenience etc.benefits by the new process.The following main conclusions were obtained by comparison conventional leaching,microwave roasting pretreatment/conventional leaching and microwave roasting pretreatment/ultrasonic leaching:(1)Leaching efficiency of germanium increased first and then there was no significant increase with an increase of the initial concentration of hydrochloric acid;Leaching efficiency of germanium increased first and then decreased with the microwave roasting temperature,microwave roasting time,leaching time,leaching temperature,oxidant dosage.And the effect of stirring rate on leaching efficiency of germanium increases is very little.The leaching efficiency of germanium increased at first and then decreased with an increase of ultrasonic power,leaching time,leaching temperature and dosage of oxidants in ultrasonic-assisted leaching.The optimal parameters were a ultrasonic power of 480 W,microwave roasting temperature of 300 ℃,microwave roasting time of 60 min,leaching time of 60 min,leaching temperature of 60 ℃,an initial hydrochloric acid concentration of 10 mol/L,a liquid/solid/oxygen ratio of 4:1:0.02,a stirring speed of 200 r/min.Under these preferred conditions,the leaching efficiency of germanium can reach 88.31%.(2)Based on the response surface optimization of germanium leaching process 3D analysis,the results showed that the initial concentration of hydrochloric acid had remarkable influence on the leaching rate of germanium,interaction of time and leaching temperature have significant influence on the leaching efficiency of germanium leaching,and the interaction of other factors is not obvious.(3)Optimized design of test parameter analysis,The optimal parameters for the extraction of germanium were a leaching time of 60.38 min,a leaching temperature of 56.40℃,,an initial hydrochloric acid concentration of 10.81 mol/L,an ultrasonic of 524.63 W.The predictive value is 89.28% and the measured value is 89.57%.The absolute error is 0.29%.The result showed that the model can well be used for optimization of the extraction of germanium from lignite ash.Compared with conventional leaching germanium and microwave roasting pretreatment/ conventional leaching,the ultrasonic wave can shorten the leaching time by 30% what improve the leaching efficiency,the microwave roasting pretreatment/ultrasonic leaching can improve the leaching rate.