Study On The Extraction Of Gold Cyanide/silver Cyanide Complexes With Graphene Oxide (GO) And GO Gel Preparing From Aphanitic Graphite

The increasing demands of gold and silver have raised new requirements for the extraction technologies of gold and silver,and it is very urgent to develop a new adsorbent with high efficiency for the extraction of gold and silver from cyanide solution.Graphene oxide,as a graphene derivative,is expected to have strong adsorption potential in the gold and silver extraction because of its huge surface area and rich functional groups.In this study,the graphene oxide prepared from cheap and abundant cryptocrystalline graphite,was used to extract gold and silver from the cyanide solution.The effects of pH,adsorption time,initial concentration of adsorbate,and adsorption temperature on adsorption were investigated.And the adsorption mechanism was studied by energy dispersive X-ray spectrometry and X-ray photoelectron spectroscopy.In order to facilitate the separation of gold/silver cyanide complexes loaded graphene oxide from cyanide solution,the graphene oxide was made into graphene oxide gel.The adsorption behavior and mechanism of graphene oxide gel for gold cyanide was explored as well.The main research contents and results of the paper are listed as follows:(1)Graphene oxide was successfully prepared from cryptocrystalline graphite through oxidation and exfoliation.Atomic force microscope showed that the thickness of prepared graphene oxide was about 1 nm.Fourier infrared spectroscopy and X-ray photoelectron spectroscopy showed that the surface of graphene oxide was rich in oxygen-containing functional groups.In addition,the porous graphene oxide gel was successfully formed through the cross-linking of polyethyleneimine and graphene oxide.(2)The experimental results of pH effect showed that the optimal pH for the adsorption of gold/silver cyanide complex on graphene oxide is 11.0 and 9.0,respectively.While that on graphene oxide gel was 9.0.The kinetic study results showed that the adsorption of gold cyanide/silver cyanide complexes on graphene oxide and gold cyanide complex on graphene oxide gels concurrently conformed to the pseudo-second-order kinetic model.Adsorption isotherm study results showed that the adsorption of gold/silver cyanide complexes on graphene oxide at 25 °C were 159.34 mg/g and 103.75 mg/g,respectively.While gold cyanide complexes adsorption capacity at 25 °C was 252.88 mg/g with graphene oxide gel as adsorbent.At the same time,it was found that increasing the adsorption temperature promoted the adsorption capacity of gold/silver cyanide complexes by using graphene oxide and graphene oxide gel as adsorbents.(3)Energy dispersive X-ray spectrometer and X-ray photoelectron spectroscopy analysis showed that gold/silver cyanide complexes distributed evenly on graphene oxide or graphene oxide gel.The possible mechanism of the adsorption was mainly attributed to the complexation between the functional groups on the surface of graphene oxide and graphene oxide gel and the gold/silver cyanide complex in the cyanide solution.