The Research On Metals Recovery From Waste Crystalline Silicon Solar Cells

With the acceleration of industrialization,the consumption of fossil energy continues to accelerate.At the same time,the use of fossil energy has led to environmental pollution.Solar energy is one of the most promising clean energy sources.The use of solar energy makes the rapid growth of the number of solar cells.As one of the rapidly growing e-waste,the recycling of solar cells after scrap can not be ignored.In this paper,waste crystalline silicon solar cells are taken as the research object,and the recovery of metal aluminium and silver is studied.Firstly,the frame and junction box were disassembled manually,and the plastic components were analyzed by thermogravimetric analysis,and the components of crystal silicon solar panels were separated by heat treatment to remove EVA.The results show that EVA can be completely decomposed by high temperature treatment at 500 ?.Among crystalline silicon solar cells,58.65% are glass,26.65% are frame,4.74% are backplane,3.09% are junction box,2.29% are battery sheet and 0.44% is confluence strip.ICP analysis showed that the contents of silver and aluminum in solar cells were 5.838mg/g and 103.165mg/g respectively.Then the aluminium in solar cells was leached by sodium hydroxide and recovered.The orthogonal experiment showed that the leaching rate of aluminum reached 93.58% when the concentration of sodium hydroxide was 0.6mol/L,the leaching time was 50 min and the solid-liquid ratio was 1:15.The precipitation rate of aluminium hydroxide is over 99% when the pH value of leaching solution is between 6 and 9.Finally,silver was leached by nitric acid and citric acid-hydrogen peroxide respectively,and silver was recovered simultaneously.In nitric acid system,when the concentration of nitric acid is 40%,the leaching time is 120 min,the leaching temperature is 70? and the solid-liquid ratio is 1:15,the leaching rate of silver is the highest,reaching 95.67%.The reaction is mainly controlled by solid membrane.The activation energy E=15.39kJ/mol.In the citric acid-hydrogen peroxide system,when the concentration of citric acid is 8g/L,the concentration of hydrogen peroxide is 25%,the leaching time is 2h and the leaching temperature is 70?,the silver leaching rate reaches 89.22%.Kinetic analysis showed that the reaction was mainly controlled by solid membrane,and the activation energy E=25.22kJ/mol was calculated.Silver in leaching solution can be recovered by ammonia-hydrazine reduction method,and the recovery of silver in leaching solution can reach more than 98%.