Study On The Adsorption Performance Of [Au（S₂O₃）₂]^3- By Chitosan Microspheres Impregnated With Aliquat-336 Extractant

With the gradual depletion of mineable high-grade gold resources and the promulgation of increasingly strict environmental laws,the traditional cyanidation method of gold extraction is difficult to adapt to the current gold production requirements.Thiosulfate gold extraction method due to its low toxicity,fast gold leaching rate,cheap leaching agent and other advantages,is considered the most promising alternative to cyanidation method of green gold extraction method.At the present stage,thiosulfate gold extraction method in gold leaching research has made great progress,but the difficulty in recovering gold from thiosulfate gold leaching solution which hindered the industrial application of thiosulfate gold extraction,seriously.In this paper,tricaprylylmethylammonium chloride（Aliquat-336）was used as extractant to extract gold from thiosulfate leaching solution;then Aliquat-336 was impregnated into chitosan to prepare modified chitosan microspheres（CMA）,and the adsorption of gold from thiosulfate gold leach solution was studied.In this paper,the performance of Aliquat-336 extraction for gold recovery and the performance of Aliquat-336 impregnated chitosan microspheres for gold recovery by adsorption were systematically investigated,the effect of CMA on gold recovery by interfering ions in the copper-ammonia-thiosulfate gold leaching system and copper-ethylenediamine-thiosulfate gold leaching system was explored,and the feasibility of using CMA in actual gold ore copper-ethylenediamine-thiosulfate leaching system was verified.The study of solvent extraction method for gold recovery showed that using ethyl acetate as diluent,Aliquat-336 at a concentration of 1.8 g/L was able to extract 100%of the gold from the thiosulfate gold leach solution by contacting it for 5 min.Gold can be extracted efficiently in a wide p H range（6～11）,but with the increase of thiosulfate concentration,gold concentration and temperature in the solution,the gold extraction rate showed a decreasing trend.The results of the reverse extraction experiments showed that the reverse extraction rate of 1 mol/L sodium chloride solution for gold in the organic phase could reach more than 97%.The experimental results of gold adsorption by Aliquat-336-impregnated chitosan microspheres showed that 0.2 g of CMA adsorbed 100 m L of[Au（S₂O₃）₂]^3-solution with gold concentration of 25 mg/L for 24 h,and the gold adsorption rate could reach95.6%;CMA showed excellent gold adsorption performance in a wide p H range;the adsorption rate of gold by CMA decreased with the increase of thiosulfate concentration and gold concentration;gold adsorption may be a heat absorption process.The isothermal adsorption process follows the Langmuir model,indicating that the adsorption is a single molecular layer adsorption,and the maximum adsorption of CMA to gold reached 20.3 mg/g.SEM-EDS,FT-IR and XPS characterization results indicate that the mechanism of gold adsorption by CMA is an anion exchange process,R₄N⁺in Aliquat-336 is adsorbed by electrostatic attraction with[Au（S₂O₃）₂]^3-.The gold-loaded CMA was eluted with 1 mol/L sodium sulfite solution and the desorption rate reached99.2%,and the CMA still had 62%gold adsorption after four adsorption-desorption cycles.The adsorption study of CMA in thiosulfate leaching gold system showed that copper ions have obvious inhibitory effect on gold adsorption,the concentration of ammonia and ethylenediamine in gold leaching solution has no obvious effect on gold adsorption,the gold adsorption performance of CMA in copper-ethylenediamine-thiosulfate leaching gold system is much suitable than in copper-ammonia-thiosulfate leaching gold system.In the copper-ethylenediamine-thiosulfate gold leaching system,CMA showed selective adsorption performance for gold,the adsorption rate of gold reached 94.7%,and the adsorption rate of copper was only 4.8%;the actual gold ore leaching in this system,using filtrate adsorption method and slurry adsorption method can recover more than 98%of gold through two stages of adsorption;the use of sodium sulfite solution can achieve the desorption of gold in gold-loaded CMA.In this thesis,gold in thiosulfate leach solution was recovered by curing extractant method,the prepared adsorbent showed selective gold adsorption performance in copper-ethylenediamine-thiosulfate gold leaching system.The research results provide an experimental reference for the development of thiosulfate gold extraction method.