Floating Au/PVP Composite Prepared By The Room Temperature Electron Reduction And Its Applications

Electron is the greenest reducing agent for preparing metal nanoparticles.The room temperature electron reduction via non-hydrogen glow discharges is a simple,easy,cheap and energy efficient way to reduce metal ions.Its outstanding features are fast nucleation and slow crystal growth.And the room temperature operation makes it possible to avoid heat effect.According to the reports,there are two steps for preparing nanoparticle film.Firstly,prepare the nanoparticles.Secondly,make the nanoparticles assemble into a film.In this work,a new method has been developed,which gold ions can be reduced,meanwhile Au nanoparticles can be assembled with poly(vinylpyrrolidone)(PVP)into a macroscopic floating film.The morphological structure and feature of the floating film can be controlled by adjusting the reaction time and the concentration of gold ions based on the results of X-ray diffraction(XRD),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).PVP acts as an assistant and stabilizer in the formation of the film according to the experiments results.And its concentration has no influence on the morphological structure or feature of the film.The nanoparticle film has a great stability.It can be stored for long time by adhering on different substrates.Also it can be transferred between different solutions without damage.Currently the demand for gold is ever increasing while the reserve of gold ore is very limited.The extraction of gold ion from various waste effluents is now a very important way for a sustainable gold supply.A new way to recover Au using a room temperature electron reduction with argon glow discharge as the electron source has a great potential because it is green,selective,simple,easy,cheap and energy efficient.In this work,the selectivity of the method is discussed by adding copper ions.And the method is also used to recover Au ion from a mimic waste stream containing Au,Zn,Fe and Cu ions.Metal ions with sufficiently high standard electrode potentials can be reduced by such electron reduction.A selective reduction of gold ion has been thereby established,where other metal ions remain in the solution.With the addition of poly(vinylpyrrolidone)(PVP),an Au/PVP floating film is rapidly formed on the surface of water within a few minutes.This makes the collection of the recovered gold very easy with very high recovery yield.The gold recovery yield reaches 87.19% in 60 s and 99.96% in 480 s under the reaction conditions tested.