Research On Recycling The Materials Of Nickel And Copper And The Performance Of Photothermal Conversion

With the rapid development of the economy,electronic products are developing in the direction of intelligence and miniaturization,and the update speed is getting faster.As a result,the number of discarded electrical or electronic equipment（e-wastes）generated is increasing.With the gradual reduction of mineral resources and the deteriorating environment for human survival,the recycling of e-waste and the development and utilization of renewable energy are essential.And as the cleanest renewable energy source,the effective use of solar energy is also the hotspot of the research.As the basic component of electronic products,printed circuit boards are made of copper clad laminates,Copper clad laminates are rich in copper resources and contain other metals,non-metallic materials and toxic and hazardous substances that can be recycled.Therefore,how to recycle copper clad laminates is the focus of current research.In this paper,the copper in the waste copper clad laminate is taken as the research object,and the copper ions are leached by the microbial method,and the copper sulfate with high purity is recovered by the crystallization method.Then Cu-MOFs and their composites were prepared by hydrothermal method,and added to water and ethylene glycol to prepare nanofluids.The thermal conductivity and photothermal conversion properties of the three carbon composites（Cu-GC、Cu₂O/CuO-GPC and Ag-GC）were investigated.Secondly,nickel-catalyzed was used to prepare a new carbon material,three-dimensional graphene,and the three-dimensional graphene/ethylene glycol nanofluid was prepared to investigate its photothermal conversion performance and thermal conductivity.The main contents and results are as follows:（1）Three-dimensional graphene is prepared by ion-exchange,nickel-catalyzed,and carbonized graphitization,using ion exchange resin as the carbon source.Three-dimensional graphene with a self-supporting structure prevents nanosheets from collecting and provides more heat transfer tunnels,and three-dimensional graphene nanofluids have significant light absorption properties.The thermal conductivity of three-dimensional graphene nanofluids is significantly higher than that of ethylene glycol.The thermal conductivity of nanofluids increases with the increase of the mass fraction of three-dimensional graphene,which is almost linear.As the mass fraction increased from 0.089%to 0.091%,the thermal conductivity enhancement rate of the three-dimensional graphene/ethylene glycol nanofluid changed linearly from 3.78%to 14.87%.With the increase of the mass concentration of the nanofluid,its photothermal conversion efficiency is also enhanced,indicating a significant increase in the ability to absorb solar energy.Three-dimensional graphene combines high thermal conductivity and high photothermal conversion efficiency,and has unique advantages in direct absorbing solar collector applications.（2）Cu₃（BTC）₂ was prepared by hydrothermal synthesis,and then a series of Cu-MOFs composites,Cu-GC,Cu₂O/CuO-GPC and Ag-GC,were prepared.The prepared three carbon materials were dispersed as additives in two base solutions of water and ethylene glycol,and the thermal conductivity and photothermal conversion effects were tested and the analysis results were compared.Compared with the thermal conductivity of ethylene glycol,the thermal conductivity of the composite nanofluids of the three carbon composites is enhanced,but the enhancement effect is relatively small.The three carbon composites can enhance the absorption and conversion of the solar heat of the base liquid.Compared with the water system,the addition of materials is more significant for the temperature increase of the ethylene glycol system.For the three carbon composites,the temperature and the Instantaneous photothermal conversion efficiency of Ag-GC nanofluids rises the fastest in both the water system and the ethylene glycol system,followed by Cu₂O/CuO-GPC,and Cu-GC is the lowest.