Recycle Of Gold From Waste Gold Plating Solution And Photothermal Conversion Performance Of Gold Nanoparticles

With the rapid development of science and technology and the ever-expanding scope of human activities,the demand for energy in human society is growing,but the traditional energy such as coal and oil are limited and cause serious environmental pollution problems.Therefore,it is urgent to develop new forms of renewable energy.As the main source of energy on the earth,solar radiation provides an effective way to alleviate energy problems.Converting light energy into heat is an important part of implementing solar energy applications.Therefore,finding excellent light absorption and heat transfer materials is a hot spot for many researchers.A large amount of gold-containing cyanide waste liquid is produced in the electroplating industry.When it is discharged into the environment,it not only causes heavy metal pollution of soil and water,but also result in precious metal resources wastes.In this study,zinc was used to recover this part of gold,combined with the latest nanotechnology to prepare gold nanoparticles and its composite materials.Gold nanoparticles shows unique optical absorption and photo-thermal conversion characteristics because of their size effect and local surface plasmon resonance effect?LSPR?,which makes them widely used in the collection of solar energy and transfer into heat energy for production and life.This study realized the resource utilization of precious metal gold in electroplating wastewater and provided new ideas for collecting solar radiation to alleviate the energy crisis.This article is divided into the following three parts:1.Gold is extracted from the waste gold plating solution by zinc substitution method,and then prepared into a chloroauric acid solution by using a saturated chlorine gas hydrochloric acid method.Using chloroauric acid as a gold source,a simple chemical reduction method was carried out using three reducing agents of trisodium citrate,ascorbic acid and sodium borohydride to obtain a near-spherical gold nanofluid of 12-23 nm.A simulated solar temperature measurement system was set up to test the temperature of the gold nanofluid under a uniform and stable xenon lamp source.The effects of the type of reducing agent and the concentration of gold sol on the optical absorption and photothermal conversion properties of nanofluids were investigated.The results show that the gold sol has a strong absorption band at 520 nm in the visible region,and the gold sol obtained with ascorbic acid and sodium borohydride has a slight red shift in the visible region absorption peak compared to trisodium citrate.The gold sol obtained by reduction of trisodium citrate has the best performance,and the radiation absorption performance and photothermal conversion performance are gradually enhanced with the increase of solid content.2.The combination of gold nanoparticles and carbon material can realize the efficient utilization of solar radiation energy and obtain a composite material with broad spectral absorption in the ultraviolet-visible-near infrared region.ZIF-8 derived nitrogen-doped graphite porous carbon?ZNG?was prepared by metal organic framework?MOF?template method.This new carbon material has a very high specific surface area(580.2 m²g^-1)and exhibits a wide absorption band in the visible and near infrared region.The gold nanoparticles with a nanometer size of 2-5 nm were deposited on the surface of the ZNG by an immersion-reduction method?Au/ZNG?.Compared to conventional carbon nanofluids such as graphene and nitrogen-doped carbon nanotubes,ZNG-H₂O nanofluids exhibit better spectral absorption properties,photothermal properties,and dispersion stability in water.When the penetration distance is 1 cm,the 100 ppm ZNG-H₂O nanofluid solar weighted absorption coefficient?A_m?is 96%and the water is 21%.Due to the synergistic effect of Au nanoparticles with LSPR effect and ZNG,Au/ZNG-H₂O exhibits enhanced photothermal conversion efficiency and has great prospects in the field of solar thermal utilization.3.Titanium nitride?TiN?is a near-infrared light-responsive nanomaterial Titanium nitride,when combined with visible-responsive gold nanoparticles,can obtain a double LSPR-effect Au/TiN composite,which is excellent for solar thermal conversion.The 100 ppm TiN-EG nanofluid can absorb 93%of the solar radiation energy,much larger than the base liquid glycol?15%?.At the same concentration,the hybrid nanocomposite?Au/TiN?has superior optical absorption compared to TiN.The light absorption characteristics and photothermal conversion properties of TiN are superior to those of other five conventional materials such as carbon nanotubes,graphene,Au,Ag and metal sulfide?CuS?.Comparing the Au/TiN nanofluids with different Au loadings,it shows that the optimal load for the current work is 5wt%,while the load is more than 5 wt%,the temperature rise of the system is not very obvious.This research provides a new idea for the collector working fluid of direct absorption solar collectors.