Resource Potential Analysis And Recycling Technology Research Of Valuable Metals In Waste LED Devices

In recent years,light emitting diodes(LED for short)have been rapidly popularized and widely used in China.With the end of its service life,a large number of LEDs will be generated into the waste stream in the future.Waste LEDs contain rare and precious metals of great resource value,but also contain a variety of toxic and harmful heavy metals,if mishandled will not only cause great waste of resources,but also bring great threats to the ecological environment and human health.This paper focuses on the resource potential of precious metals contained in waste LED devices and their resource recovery technology.By establishing the model and combining experimental data to predict and evaluate the production and resource potential of waste LED devices in China;Using"heat treatment-grinding-screening"technology to separate and enrich the precious metals in LED devices,and the pre-treated rare metals collective using"oxidative roasting-mixed acid leaching"method for rare precious metals recovery,so as to achieve high-efficiency leaching of precious metals Au and Ag by optimizing reaction conditions through single-factor experiment.The resource potential analysis results of precious metals in waste LED devices in China show that under the three situations of conservative,general and optimistic consumption in the future,the annual scrap volume of LED in China will reach 4184.6 billion to 6028.5 billion by2025,the annual production of waste LEDs will reach 1.07 million tons to 1.54 million tons,and the total amount of LED scrap will reach 3.55 million tons to 4.74 million tons from 2003to 2025.Under the general situation,the total potential metal resources in end-of-life LEDs in China will reach 880,000 tons from 2003 to 2025,of which Cu's content is the largest,up to610,000 tons,accounting for 69%of the total potential resources,rare and precious metals Ga,Au and Ag are 1011 tons,275 tons and 163 tons respectively.By 2025,the total value of its resource could reach 108.3 billion,of which Au has the highest economic value,reaching 80.4billion,accounting for 74%of the total value,followed by Cu at 23 billion,Ga at 1.4 billion,and Ag at 600 million.The pre-treatment technology of"heat treatment-grinding-screening"can realize the efficient separation and enrichment of rare metals in waste LED devices,and the optimum heat treatment conditions are:under roasting conditions,after heating to 450?at a heating rate of10?/min,then stop heating and cool to room temperature naturally.After grinding and screening,the metal Ga,Au,Ag,Ca,Al and other metals are mainly concentrated in d<600?m of small particle size,the concentration content of 2299 mg/kg,13655 mg/kg,2188 mg/kg,44744 mg/kg,44632 mg/kg,which are about 11.1 times,12 times,15.9 times,10.4 times,4.8times richer than the initial raw materials.The metal Cu,Fe,Ni,Zn,Pb and other metals in d>600?m of the large particle size,the concentration content of 1056926 mg/kg,29223 mg/kg,3284 mg/kg,1354 mg/kg and 1850 mg/kg,which are about 1.9 times,2.1 times,1.7 times and1.4 times more intensive than the initial raw material concentration,while Pb does not get enriched.The results of the resource recovery of rare precious metals show that"oxidizing roasting-mixing acid leaching"can achieve efficient leaching of precious metals Au and Ag,while the recovery efficiency of Ga is low.The best recovery conditions explored through single-factor experiments are:oxidation roasting temperature of 700?,3.75 mol/L HCl+1.25 mol/L CH₃COOH,leaching temperature is 80?,solid-liquid ratio is 10 g/L,leaching time is 4h,Fe Cl3 addition is 50%,the leaching rate of Au and Ag are 99.3%and 91.5%respectively,the Ga is 20.8%.The leaching kinetics analysis show that the leaching process of Au in this study system is mainly controlled by chemical reaction,which can promote the leaching of Au by increasing the reaction temperature,acid concentration and adding oxidants.