Design, Synthesis And Properties Of New Materials For Selective Adsorption Of Gold

In recent years,the demand of gold has been increasing in the industrial and economic fields,but its non-renewability makes it particularly urgent to recover gold from secondary resources such as gold-bearing waste liquor.In this study,the grafting material D301-g-PGMA was obtained by constructing oxidation-reduction initiating system to graft the monomer GMA onto the surface of D301.Then,arginine（Arg）,1,3-thiosemicarbazide（TCH）,aminoguanidine hydrochloride（AG）and thiosemicarbazide（TSC）were used to modify the grafted material,and four new functional materials（ArgD301,TCHD301,AGD301 and TSCD301）were successfully prepared,respectively.Subsequently,a surface imprinting material IIPTSCD301 was prepared by surface imprinting technique.The adsorption and recognition selectivity of different materials towards AuCl₄^-were studied.In the preparation of ArgD301,the ring-opening rate of the prepared ArgD301 was 62±2%under the conditions of Arg dosage 3.0 g,reaction temperature 90℃,stirring time 10 h.The results showed that ArgD301 had good adsorption and recognition performance towards AuCl₄^-.The pH and temperature had a great influence on the adsorption capacity.At pH of 2,the equilibrium adsorption capacity of ArgD301 towards AuCl₄^-was 451.67 mg·g^-1.The adsorption behavior of ArgD301 towards AuCl₄^-was a typical Freundlich monolayer adsorption.The parameters of adsorption thermodynamics indicated that the adsorption process of ArgD301 towards AuCl₄^-was endothermic and spontaneous.When the ArgD301mass was 0.05 g,the adsorption efficiency could reach 97.43%at 0.75 h.The selectivity coefficient of ArgD301 towards AuCl₄^-was 225.23 relative to CuCl₄^2-.In addition,ArgD301also had good reusability performance.In the preparation of TCHD301,the ring-opening rate was 55±2%under the conditions of TCH dosage 1.5 g,NaOH concentration 1 mol·L^-1,reaction temperature 80℃,stirring time 12 h.The results showed that TCHD301 had good adsorption and recognition performance towards AuCl₄^-.The equilibrium adsorption capacity of TCHD301 towards AuCl₄^-could reach 566.59 mg·g^-1at 25℃and pH of 2,the adsorption process fitted well with pseudo-second-order model.When TCHD301 mass was 0.05 g,the adsorption efficiency could reach 98.23%at 1 h.In the binary mixed system of gold and copper,the selectivity coefficient of TCHD301 towards AuCl₄^-was 556.20 relative to CuCl₄^2-.In addition,the adsorption capacity of TCHD301 did not change significantly during the reuse process.In the preparation of AGD301,the ring-opening rate was 87±2%under the conditions of AG dosage 1.2 g,reaction temperature 90℃,stirring time 8 h.The results showed that the equilibrium adsorption capacity of AGD301 towards AuCl₄^-could reach 580.36 mg·g^-1.The pH and temperature had a great influence on the adsorption capacity,and the higher the temperature,the better the adsorption capacity.The adsorption behavior was a typical monolayer adsorption.The fitting results of adsorption thermodynamics indicated that adsorption process was endothermic and spontaneous.The selectivity coefficient of AGD301towards AuCl₄^-was 345.90 relative to CuCl₄^2-.In addition,AGD301 also had good chemical stability and and reusability.In the preparation of TSCD301,the ring-opening rate was 75±2%under the conditions of TSC dosage 2.5 g,NaOH concentration 1 mol·L^-1,reaction temperature 80℃,stirring time10 h.The results showed that TSCD301 had a strong adsorption ability towards AuCl₄^-.At25℃and pH of 2,the equilibrium adsorption capacity of TSCD301 towards AuCl₄^-could reach 658.77 mg·g^-1.The fitting results of kinetics and adsorption isotherm showed that the adsorption of TSCD301 towards AuCl₄^-fitted well with the pseudo-second-order kinetics model and Freundlich model.In the binary mixed system,the selectivity coefficient of TSCD301 towards AuCl₄^-was 409.32 relative to CuCl₄^2-.By comparing the four adsorbents,the results indicated that the adsorption capacity of adsorbent depended on the number and type of active sites on the surface of adsorbent.Surface ion imprinting material（IIPTSCD301）with specific recognition selectivity and excellent adsorption performance towards AuCl₄^-was successfully prepared by the surface imprinting technology,using AuCl₄^-as template ion and EGDE as crosslinking agent.The results showed that pH and temperature had a significant influence on the adsorption performance.The adsorption thermodynamics indicated that adsorption process was spontaneous and became better at higher temperature.In mixed systems,the selectivity coefficient of IIPTSCD301 towards AuCl₄^-could reach 1462.00.When IIPTSCD301 mass was 0.05 g,the adsorption efficiency could reach 97.54%at 2 h.In addition,IIPTSCD301also had excellent reusability performance.