Experimental Study On The Recovery Of Tellurium From Cadmium Telluride Waste

Cadmium telluride is an important semiconductor material,because of its high light absorption performance,the module is not easy to decompose at high temperature and so on,so it is widely used in the field of light absorption.The development of the cadmium telluride photovoltaic industry is very rapid,but the shortage of tellurium resources has become a major problem limiting the development of cadmium telluride photovoltaic technology.Recovering tellurium resources from cadmium telluride-containing photovoltaic decommissioned components and reusing rare metals can alleviate the shortage of tellurium resources.The existing cadmium telluride photovoltaic waste treatment process is mainly based on hydrometallurgy,which not only has a long process,high pollution and high energy consumption,but also causes harm to the environment.This article is the first to propose the use of sulfidation-multi-stage vacuum distillation technology for the treatment of cadmium telluride photovoltaic waste,aiming to realize the recycling of tellurium resources with high efficiency.This paper reviews the distribution of tellurium resources and the current status of tellurium recovery in cadmium telluride waste;it also discusses in depth the thermodynamics and kinetics of the sulfidation reaction and vacuum distillation process.Sulfur is added to the reaction system,and sulfur and cadmium telluride undergo a displacement reaction to produce elemental tellurium with a high saturation vapor pressure.When the sulfide product is vacuum distilled,tellurium is enriched in the gas phase,and cadmium sulfide is enriched in the residue.Kinetic studies indicate that the main factors affecting the rate of sulfurization reaction are temperature,sulfur concentration,and liquid flow state.The main factors affecting the evaporation rate of elements in the distillation process are the difference in tellurium concentration,distillation temperature,evaporation area,and system pressure.The evaporation sequence of sulfur,tellurium,and cadmium sulfide in the sulfide product is: sulfur> tellurium> cadmium sulfide.The vulcanization reaction temperature is 400 ℃,the ratio of cadmium telluride and sulfur is 1: 1.1,and under argon conditions,the sulfide smelting products are tellurium and cadmium sulfide.The vulcanized product was subjected to vacuum distillation experiment under the conditions of 700 ℃,residual pressure of 15 Pa and holding time of 30 min.The purity of tellurium can reach 99.54%,the content of cadmium and sulfur in tellurium is 0.047% and 0.41%,and the recovery rate of tellurium is 98%.Two-stage vacuum distillation to remove Cd and S from crude tellurium showed that: the distillation temperature is 450 ℃,the holding time is 20 min,and the residual pressure is 15Pa(air).The raw material volatilization rate is 97.37%,and the sulfur and cadmium content in the collected condensate is 0.0056% and 0.34%.The removal rate of cadmium in crude tellurium is 90.82%.When the distillation temperature was 400 ℃,the holding time was 20 min,and the residual pressure was 15 Pa,the cadmium and sulfur contents in the residue were 0.0061% and 0.0194%,respectively,and the sulfur removal rate was 94.29%.This paper first proposes a new process for recovering tellurium from cadmium telluride using displacement reaction-multistage vacuum distillation technology.This technology is highly consistent with the principle of "reduce,reuse and recycle" of solid waste,and is sustainable for the photovoltaic industry.Development provides the foundation...