Preparation Of Nano-silica Composite Material And Its Adsorption Performance For Gold

Gold has excellent performance and has a wide range of applications in various industrial fields such as jewelry and currency reserve.Moreover,it also plays a specific role in the fields of electronic materials,catalysts,biomedicine and so on.However,as the demand for gold grows,the amount of gold resources is declining.A large amount of gold containing waste produced in the fields of electronic plating,chemical engineering and metallurgy not only caused serious environmental pollution,but also made a great waste of gold resources.In this thesis,nano-silica oxide was used as the base material,which was modified with organic functional molecules and three novel materials were prepared for the selective adsorption of gold ions,which provided a new idea for the enrichment and recovery of gold ions.The results showed that:（1）First,the silane coupling agent was grafted on the surface of nano silica,then the intermediate products were combined with the silane coupling agent by surface polymerization.Finally,AMPD,GD and PDMC were modified to the surface of nano silica through the reaction of epoxy group,benzene ring and amino group.Three new types of nano adsorbents were prepared.The nanocomposites were characterized by FT-IR,TGA,XPS and TEM.（2）The 4-（Aminomethyl）pyridine modified nano-silica can selectively absorb gold ions from aqueous solution.The maximum adsorption capacity was 55.5 mg/g at pH 4,the adsorption equilibrium time was 30 min.The adsorption isotherms followed the Langmuir isotherm and the adsorption kinetics fitted well with the pseudo-second-order kinetic model,the adsorption of gold ions is a monolayer adsorption and the rate-determining step is chemical adsorption.It has a certain selective adsorption of gold ions.The adsorption rate decreased only by 3.1%after 5recycling cycles,indicating the adsorbent has good reusability.The adsorption mechanism is ascribed to the ion exchange and complexation between amino,hydroxyl and gold ions.（3）The bis-trifluoromethane sulfonamide（Nft₂）/1H-pyrazole-1-carboxamidine hydrochloride modified nano-silica has good selective adsorption for gold ions,the maximum adsorption capacity for gold ions was 120.56 mg/g at p H 5.The adsorption kinetics followed the pseudo-second-order kinetic model and the adsorption isotherms fitted well with the Hill isotherm.The n value in the Hill model is 1.29,indicating that each adsorption site can adsorb 1.29 ions.The adsorbents have good reusability and selective adsorption of gold ions.（4）The poly（methacryloxyethyltrimethyl ammonium chloride）modified nano-silica can selectively absorb gold ions from aqueous solution,the adsorption equilibrium time was 20 min and the maximum adsorption capacity for gold ions was127.3 mg/g at pH 3.The adsorption isotherms followed the Langmuir isotherm and the adsorption kinetics fitted well with the pseudo-second-order kinetic model.The adsorbent has good selectivity and regeneration ability.The separation factors for magnesium,strontium,lead,and copper ions are:6.49,37.00,67.00 and 33.48.The adsorption mechanism is ascribed to the ion exchange between quaternary ammonnium and gold ions...