| With the rapid development of economy and society,the rapid growth of demand for liquid crystal display,has brought convenience to people's lives,but also caused serious environmental pollution and resource waste,resource recycling of waste liquid crystal display,can not only play a role in the protection of the environment,but also bring huge economic value and social value to society.In this paper,the recovery of indium from waste liquid crystal displays is studied.Microwave leaching pretreatment is used to enhance the leaching of indium from waste liquid crystal displays.First,the process of the waste liquid crystal display is systematically studied.Through the manual disassembly of the waste liquid crystal display,the internal structure of the waste liquid crystal display is recognized,and the components of the disassembled liquid crystal display are obtained.The glass substrate material of the liquid crystal display is used as the original sample for the next heat treatment.Through the TG-DSC test,the thermal decomposition temperature of the liquid crystal display glass substrate is determined to be between 300 and 470 ?.Using the technology of XRF,ICP-AES and element analysis,it is determined that the glass substrate of liquid crystal display is alkali free aluminosilicate glass based on SiO2 and Al2O3,with ITO film on the surface,and the more content of indium is in the glass substrate with smaller particle size.When the particle size of the glass substrate is less than 0.4 mm,the content of indium is 311mg/kg.The waste liquid crystal display was treated by Microwave Roasting Pretreatment acid leaching process.The waste liquid crystal panel was treated under the conditions of microwave roasting temperature 300 ?,4 min and additive dosage 500 g/kg.Then 5 mol/L sulfuric acid solution was used to extract 90 min at 90 centigrade,and the liquid solid mass ratio was 8 mL/g.The leaching rate of indium is 92.3%,which is 28.8% higher than that of untreated leach.The maximum leaching rate is 63.5%.According to the results of single factor experiment,the four parameters of Microwave Roasting Pretreatment time,leaching time,leaching temperature and liquid solid ratio are the independent variables.The process optimization of the waste liquid crystal display is carried out by response surface method.The optimum experimental condition of microwave roasting to strengthen acid leaching is predicted by the fitting response surface model equation: leaching time 97.5 min,the pretreatment time of microwave roasting is 4.54 min,the leaching temperature is 90 ?,and the ratio of liquid to solid is 7.56 ml/g.The leaching rate of indium is 92.43% under this optimal experimental condition.The factors affecting the leaching are: Microwave Roasting Pretreatment time > liquid solid ratio > leaching time > leaching temperature,so BBD response surface method is used to seek the best microwave roasting It is of practical value to process indium by intensification.The leaching reaction kinetics study shows that leaching temperature and initial concentration of sulfuric acid have significant influence on the leaching reaction of the glass substrate powder of the waste liquid crystal display.The leaching rate of indium in the glass substrate powder of the waste liquid crystal display is significantly increased with the increase of the leaching temperature and the increase of the initial concentration of the sulfuric acid.The untreated leaching and microwave roasting enhanced leaching process of waste liquid crystal display glass substrate can be described by Avrami equation.In the process of microwave roasting,the apparent activation energy of the leached liquid crystal display glass substrate has never been reduced to 11.8 kJ/mol,the apparent reaction progression from 0.48 to 0.37,and the leaching process from the untreated leaching to the internal diffusion control of the microwave roasting pretreatment.The results will provide favorable technical support for resource utilization of waste liquid crystal panels. |
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