Study On Adsorption Characteristics Of Activated Carbon And Its Adsorption Of Gold Thiosulfate By Ion

Thiosulfate gold leaching has gained extensive attention because it is of environmentally friendly technique and it can be used for refractory ores. However, there is no effective method to recovery gold from thiosulfate leaching solution, which makes the leaching be uneconomical compared with the process of carbon in pulp (CIP). Activated carbon is the most desired adsorbent and has been widely used to recovery gold in cyanidation. But it is poor adsorbability for Au(S2O3)23-, which hinders the industrial application of thiosulfate. Therefore, the research on activated carbon which can effectively adsorb gold from thiosulfate leaching is of great significance for industrial application.In this paper, different methods to modify activated carbon to improve the adsorption ability for Au(S2O3)23- were introduced. At last, the activated carbon effective adsorption of gold was prepared. The XRD, BET and FTIR methods were employed to analyze the crystal species, specific area, total pore volume, and surface chemical property of the modified activated carbon, and the XPS was used to analyze the valence state of element. In addition, the adsorption mechanism and the influence of various ions on the gold adsorption were discussed.The results indicated that the original activated carbon was nearly no adsorption capacity for Au(S2O3)23-. The modified activated carbon with prussian-blue analogues prepared by cupric ferrocyanide and silver ferrocyanide can adsorb gold effectively. Through optimization of the carbon modifing process "Impregnation of transition metal salt solution-Roasting-Impregnation of potassium ferrocyanide solution", the gold adsorption rate of the modified activated carbon with cupric ferrocyanide and silver ferrocyanide was 85.7% and 78.9% respectively.The results of adsorption experiments shown that, the appropriate dissolved oxygen at higher temperature in solution were good for adsorption gold by AC-CuFC and AC-AgFC. The FTIR and XPS were used to analyze adsorption process; the results indicated that Au+ was exchanged with H+、Cu2+ or Ag+ which were on the surface of the modified activated carbon. then, Au+ was reduced to native gold by Fe(CN)64-Through the adsorption isotherm linear fitting, it was found that the adsorption of both AC-CuFC and AC-AgFC followed the Freundlich isotherm model well. However, under different temperatures and gold concentrations, a pseudo-second order kinetic model was suitable for the adsorption kinetic of AC-CuFC; Intraparticle diffusion model was suitable for the adsorption kinetic of AC-AgFC. At a gold concentration of 100 mg/L at 40℃, the gold adsorption capacity for AC-CuFC and AC-AgFC were 2.81kg/t and 3.35kg/t respectively.Study on the influence of the leaching reagents, sulfur ions and metal ions on gold adsorption, the results shown that the gold adsorption rate of AC-CuFC gradually decreased as the concentration increase of Cu2+, NH3, en, S2O32-, SO42-, SO32- and S4O62-respectively; and the gold adsorption rate increased as the molar ratio increase of NH3/Cu2+ or en/Cu2+. The influence of metal ions on gold adsorption was more complex; the existence of small amount (5 mg/L) Ag+, Pb2+, Zn2+, Co2+in solution, which can promote the gold adsorption rate of modified activated carbon; but the higher concentration of Ag+, Pb2+, Zn2+, Co2+ in solution, it lead to generate hydroxide precipitation (Me(OH)x) to covering the surface of activated carbon, hindered the gold adsorption of modified activated carbon. The influence of metal ions on the gold adsorption rate was order as follows:Zn2+> Co2+ ≈ Pb2+> Ag+.The results of desorption experiment shown that,0.5 mol/L sodium sulfide has the advantages of high and fast desorption rate. Regeneration process shown that O.lmol/L hydrogen peroxide for desorption active carbon has better performance of regeneration. Through 5 times cycle test of modification-adsorption-desorption-regeneration process shown that the gold adsorption rate of the modified activated carbon can reach 80%, and indicated that the modified activated carbon has a good application prospect for adsorption Au(S2O3)23-...