Preparation Of AuCl₄^- Surface Imprinted Material And Its Selective Properties

Gold has many applications in production and life,but as a result of its rarity and high price,the recovery of gold from various gold-containing resources has become the focus of attention.The grafting material D301-g-PDMDAAC was prepared by using surface graft polymerization method.The best conditions in the process of preparing D301-g-PDMDAAC were the volume of DMDAAC was 10 m L,w（APS）was 1%,the reaction temperature was40℃,and the reaction time was 10 h.D301-g-PDMDAAC reached adsorption equilibrium after adsorbing AuCl₄^-for 28 h at 25℃,p H=2 and the adsorption capacity reached 371.92mg·g^-1.The adsorption behavior conforms to the Lagergren-first-order kinetic model and Freundlich monolayer adsorption.The selectivity coefficient k of D301-g-PDMDAAC to AuCl₄^-reached 7.51 in the binary mixed solution of AuCl₄^-and Cu Cl₄^2-.The adsorption efficiency reached 98.7%with the dosage of adsorbent was 0.025 g.In addition,D301-g-PDMDAAC also has good reuse performance.The grafting material D301-g-PVIM was prepared by using surface graft polymerization method,which was characterized by FTIR and SEM.The D301-g-PVIM with the best adsorption performance for AuCl₄^-was prepared under the condition that the volume of VIM was 8 m L,the reaction temperature was 40℃,w（APS）was 0.4%,and the reaction time was10 h.D301-g-PVIM reached adsorption equilibrium after adsorbing AuCl₄^-for 36 h at 25℃and p H=2 and the adsorption capacity reached 478 mg·g^-1.The adsorption behavior fits the Pseudo-second-order kinetic model well and belongs to the Freundlich monolayer adsorption.Compared with Cu Cl₄^2-,the adsorption selectivity coefficient k for AuCl₄^-was 16.43.The adsorption efficiency reached 99.45% with the dosage of D301-g-PVIM was 0.045 g,and almost all the AuCl₄^-in the solution could be recovered.In addition,D301-g-PVIM also have good regeneration performance.The surface ion-imprinted material D301-g-IIPDMDAAC was prepared by using AuCl₄^-as template,DMDAAC as monomer and MBA as cross-linking agent by the method of simultaneous surface grafting and imprinting.During the preparation process,the volume of DMDAAC was 5 m L,n（AuCl₄^-）:n（DMDAAC）was 0.06%,the amount of APS was 1.6%,the amount of MBA was 6%,and the amount of D301 was 0.3 g,D301-g-IIPDMDAAC with the best adsorption capacity for AuCl₄^-was prepared.The adsorption equilibrium time was 36h and the adsorption capacity of AuCl₄^-was 434.4 mg·g^-1 at 25℃and p H=2,which is much larger than the adsorption capacity of the non-imprinted material D301-g-NIPDMDAAC(266.2 mg·g^-1).In the binary-mixed solution of AuCl₄^-/Cu Cl₄^2-and AuCl₄^-/Fe Cl₂,the adsorption selectivity coefficient k of D301-g-IIPDMDAAC reached 108.96 and 63.38,respectively.Compared with the graft material D301-g-PDMDAAC,the adsorption capacity of D301-g-IIPDMDAAC towards AuCl₄^-was increased from 371.92 mg·g^-1 to 434.4 mg·g^-1and the selectivity coefficient k was increased from 7.51 to 108.96,which was a 14-fold increase.It shows that D301-g-IIPDMDAAC has good selective adsorption performance for AuCl₄^-.The adsorption behavior fits well with the Pseudo-second-order kinetic model and belongs to Langmuir monolayer adsorption.During the adsorption process,one AuCl₄^- molecule occupies one imprinted cave.The adsorption process was proved to be spontaneously endothermic.Moreover,D301-g-IIPDMDAAC also has good regeneration performance.The surface ion-imprinted material D301-g-IIPVIM was prepared by using AuCl₄^-as a template,VIM as monomer,MBA as cross-linking agent by the method of simultaneous surface grafting and imprinting.When the volume of VIM was 6 m L,n（AuCl₄^-）:n（VIM）was0.08%,w（APS）was 0.8%,w（MBA）was 2.5%,and the amount of D301 was 0.3 g,D301-g-IIPVIM with the best adsorption performance for AuCl₄^-was prepared.The adsorption equilibrium time was 48 hours,and the adsorption capacity of AuCl₄^-was 448.5mg·g^-1 at 25℃and p H=2,which is higher than that of non-imprinted material D301-g-NIPVIM(251.6 mg·g^-1).In the binary-mixed solution of AuCl₄^-/Cu Cl₄^2-、AuCl₄^-/Fe Cl₂,the selectivity coefficient k of D301-g-IIPVIM to AuCl₄^-reached 183.8 and43.47,respectively,which is much larger than the selectivity coefficient of D301-g-NIPVIM.Compared with the D301-g-PVIM（selectivity coefficient 16.43）,the selectivity coefficient is increased by 11 times,indicating that D301-g-IIPVIM has excellent adsorption selectivity for AuCl₄^-.The adsorption behavior conforms to the Pseudo-second-order kinetic model and can be described by the Langmuir isotherm model.The protonated N atom on the imidazole ring and the imprinted caves simultaneously combined with the AuCl₄^-to promote the adsorption process,which belongs to the monolayer adsorption.In addition,D301-g-IIPVIM has good reuse performance.