Synthesis Of Modified Multi Walled Carbon Nanotubes For Adsorption Of Dold And Bismuth

With gold and bismuth widely used in various fields of production and life,the demand is increasing and natural resources are decreasing,so it is very important to study the enrichment of gold and bismuth ions from environmental samples.As a new type of nano material,carbon nanotubes have unique structure and excellent properties,which can be modified by surface modification to improve the surface properties,and enrich metal ions in the environment.In this paper,the modified multi walled carbon nanotubes as solid phase extraction adsorbents were used to the adsorption and recovery of gold and bismuth ions.In this paper,three kinds of modified multi walled carbon nanotubes adsorbents have been prepared by chemical modification.The intermediate medium?mSiO₂@MWCNTs?was synthesized of the mesoporous silica coated on the surface of MWCNTs,and then TSC and MPTS were grafted on the mSiO₂@MWCNTs,respectively.The two of new materials were marked as TSC-mSiO₂@MWCNTs and MPTS-mSiO₂@MWCNTs,respectively.The third was the polydopamine modified to the surface of MWCNTs,the obtained material was marked as PDA@MWCNTs.The MWCNTs,mSiO₂@MWCNTs,TSC-mSiO₂@MWCNTs,MPTS-mSiO₂@MWCNTs,PDA@MWCNTs were characterized by various techniques such as FT-IR,SEM,EDX,TEM,TGA and N2 adsorption-desorption isotherm.It was proved that the modified multi walled carbon nanotubes were synthesized successfully by compared with the results of the analysis.Based on study of the properties of adsorption gold ions by TSC-mSiO₂@MWCNTs,related variables such as contact time,initial concentration,solution pH,adsorbent dosage,salt concentration,temperature and other conditions were optimized in static adsorption experiment.It was found to be the contact time was 360 min,the concentration of 50 ?g mL-1,the original pH value of Au?III?solution,20 mg adsorbent,the temperature of 303 K were the optimum conditions.The maximum adsorption capacity of Au?III?was 124.20 mg g-1,the adsorption kinetics can be described by the pseudo-second-order kinetic equation,the adsorption isotherm accords with the Langmuir isotherm model,and the adsorption thermodynamics analysis shows that the adsorption was a spontaneous exothermic process.And the maximum recovery of Au?III?was 100% by the dynamic adsorption behavior.Based on the investigation of the adsorption selectivity of Au?III?in binary systems and waste printed circuit board,the selectivity factor Kd of TSC-mSiO₂@MWCNTs to Au?III?was 307.5 in the binary systems,and the adsorption rate of Au?III?was up to 89.87 % in the waste printed circuit board solutions.In the properties of adsorption metal ions by two kinds of adsorbents was investigated.The experimental conditions were optimized by single factor experiment.The maximum adsorption capacity of the two adsorbents for Au?III?were 124.36 and 496.33 mg g-1,respectively.And the maximum adsorption capacity of the two adsorbents for Bi?III?were 117.01 and 114.67 mg g-1,respectively.It was proved that the adsorption process of Au?III?and Bi?III?were in accordance with the pseudo-second-order kinetic equation and Langmuir isotherm model.The adsorption process of Au?III?was a spontaneous endothermic reaction,while Bi?III?was Spontaneous exothermic and spontaneous endothermic reaction,respectively.The adsorption-desorption behaviors were studied by solid phase extraction experiment,under the optimal conditions,the maximum recovery rate of the two adsorbents for Au?III?were 100 % and 93.37 %,respectively.The maximum recovery rate of the two adsorbents for Bi?III?were 96.05 % and 85.61 %,respectively.In the field of environmental application,the adsorption studies of binary systems containing Au?III?and other metal ions,the selectivity factor Kd of the two adsorbents for Au?III?were 828.33 and 1456.99,respectively.The extraction of Au?III?from waste printed circuit board was studied,the adsorption rate of the two adsorbents Au?III?were 62.10 % and 85.23 %,respectively.The results proved that the three kinds of modified multi walled carbon nanotube adsorbents had good performance,and the process is simple and easy to operate,green environmental protection.It may provide a reference basis for the study of enrichment and separation of gold,bismuth ions in environmental samples.