Preparation Of Nitrogen-rich Polystyrene Mesoporous Microspheres And Their Adsorption Properties For Au(S₂O₃)₂^3-

Thiosulfate gold leaching has attracted extensive attention because of its advantages of non-toxicity,environmental friendliness,an efficient gold leaching rate,and strong adaptability to complex ores.However,the higher-cost and inefficient of gold recovery in the thiosulfate leaching system have impeded its industrialization process.Industrial application of modified activated carbon,silica gel,and resin for gold recovery in the thiosulfate system has been limited,mainly due to the complicated modification process,unstable properties and easy pulverization.Therefore,it is crucial to develop an adsorbent with easy prepareation,high stability and strong rigidity for the development of thiosulfate gold leaching,especially with the property of excellent ability for gold adsorption.In this dissertation,nitrogen-rich polystyrene amine mesoporous microspheres（PS-TETA）and azole mesoporous microspheres（PS-3-AT）were prepared through the functionization of chloromethylated polystyrene（PS-Cl）with triethylenetetramine（TETA）or 3-amino-1,2,4-triazole（3-AT）.These products were employed in the recovery of Au（I）in the thiosulfate leaching system.Firstly,the synthesis conditions and adsorption properties of functionalized microspheres were investigated by the monofactor analysis.Secondly,FT-IR,BET and XPS were used to clarify the structural properties of functional microspheres and the interaction mechanism with Au（S₂O₃）₂^3-.Finally,functional microspheres were applied to the recovery of gold from copper-ammonia（ethylenediamine）-thiosulfate gold leaching solution for testing its practical application performances.The results showed that the PS-TETA possessed a best adsotpion effect for Au（S₂O₃）₂^3-under these synthetic conditions,the molar ratio of PS-Cl to TETA was 1:2,the reaction solvent was tetrahydrofuran,stirred at ambient temperature for 2 h.The maximum gold loading reached 23.79 mg/g.The adsorption behavior of Au（S₂O₃）₂^3-on the surface of PS-TETA microspheres was consistent with Freundlich isothermal model and psuedo-second order model.Thermodynamic experiments indicated that the adsorption process was exothermic and spontaneous.BET showed that PS-TETA is a mesoporous material.The results of FT-IR and XPS showed that the adsorption mechanism of PS-TETA for Au（I）is anion exchange.The desorption ratio of gold-loading PS-TETA microspheres was 87.2%when 0.1 mol/L Na₂SO₃ was used as the desorbent.Moreover,the adsorption ratio of PS-TETA for Au（S₂O₃）₂^3-can still reach85%after five cycles.However,in the investigation of various leaching components,it was discovered that Cu²⁺had a significant inhibitory effect on amine microspheres for the adsorption of Au（I）.Additionally,amine microsphere exhibited poor adsorption effect in the industrial gold leaching solution.Given that the practical application performance of PS-TETA microspheres was limited,PS-3-AT microspheres were produced by grafting the 3-AT with conjugated structure as functional groups on the surface of chlorine spheres.The results showed that the optimal synthesis conditions of PS-3-AT was as follows,1 mol of PS-Cl was swollen in anhydrous ethanol of 100 m L for 3 h,and then reacted with 2 mol of 3-AT at 80℃for 12 h.The adorption capacity of PS-3-AT for Au（S₂O₃）₂^3-approached 39.8mg/g.The adsorption behavior conformed to the Freundlich isothermal model and the psuedo-second order model,respectively.The adsorption was also an exothermic process.PS-3-AT can efficiently adsorb Au（S₂O₃）₂^3-in p H range from 4 to 11.The desorption ratio of PS-3-AT-Au microspheres in 2 mol/L Na Cl solution can reach 97.9%,and the adsorption ratio of PS-3-AT remains above 75%after five cycles.In addition,PS-3-AT microspheres preformed the strong anti-interference ability which can completely recovery gold in the actual Cu²⁺-NH₃-S₂O₃^2-and Cu²⁺-en-S₂O₃^2-systems,and indicating that PS-3-AT is more promising in the industrial application.Besides,the synthesis mechanism of PS-TETA and PS-3-AT microspheres was analyzed by quantum chemical calculation.The functionalization process mainly occurred between active chlorine and primary amine.Independent gradient model analysis revealed that weak interactions are main intermolecular forces between the functionalized microspheres and Au（S₂O₃）₂^3-.In this dissertation,nitrogen-rich polystyrene amines and azole mesoporous microspheres were synthesized and successfully applied to gold recovery from thiosulfate solution,providing theoretical reference and experimental basis for the development of thiosulfate gold leaching.