| Along with the speed development of industries and new rising industries,the water-borne metal pollution has increasingly been a severe environmental problem.As an essential microelement of organisms,the Copper in the environment is easily access to the human body via the biological chain.Once the concentration of copper ions in the environment exceeds the standard,it will pose a serious threat to the human body.In order to protect the environment and human health,it is of great significance to study new technologies and methods for effectively removing superfluous copper ions in the environment.This paper will use high molecular polymer polyacrylonitrile as raw material and take the high-voltage electrospinning technology to prepare polyacrylonitrile electrospun fiber membranes which is featured by uniform diameter,good appearance,and smooth surface,at the same time it is easy to extend surface chemical modification.And also the paper mainly study the effects of spinning solution concentration and spinning voltage on the morphology of electrospun nanofiber membranes and sum up the optimal electrospinning conditions.Polyacrylonitrile nanofiber membranes are chemically modified with sodium hydroxide-ethylene glycol solution to obtain and the adsorption behavior of copper ions in aqueous solution is also been studied in detail.we draw to the following main conclusions through experimental research:(1)Taking polyacrylonitrile as raw material and dimethylformamide as solvent,and the polyacrylonitrile nanofiber membranes with an average diameter of 400 nm is successfully prepared via electrospinning technology.This paper pay emphasis on the effect of spinning solution concentration and spinning voltage on the appearance structure of spinning fibers.Based on the results of previous studies,we summarize the optimal electrospinning conditions for preparing polyacrylonitrile nanofiber membranes:when the spinning solution injection speed is 1 mL/h,and with a distance of 14 cm between the spinning needle and the collector,a mass fraction of 6 wt%of the spinning solution,at a voltage of 12 to 13 kV,its possible to produce a uniform and smooth polyacrylonitrile eletrospun fiber.(2)The polyacrylonitrile nanofiber membrane prepared with the electrostatic method is chemically modified with an organic solution of sodium hydroxide.This paper mainly analysis the effects of reaction temperature,NaOH concentration,and reaction time on the material modification,and combines the comprehensive analysis of the appearance morphology of the material,the conversion of the nitrile group,and the softness of the material,we concluded the best modification conditions:at 70℃,the polyacrylonitrile nanofiber membrane is reacted in 10 wt%sodium hydroxide glycol solution for 2 h.The modified polyacrylonitrile nanofiber membrane prepared under the experimental conditions is subjected to Fourier infrared analysis and thermogravimetric analysis.According to the analysis results of FT-IR,the modification reaction is very successful and the modification reaction mechanism-cyclization reaction is also inferred.According to the TGA curve analysis,we conclude that the thermal stability of the modified polyacrylonitrile nanofiber membrane has been deteriorated.(3)Utilize modified polyacrylonitrile nanofiber membranes to adsorb trace copper ions in water and study the effects of solution pH,adsorbent dosage,adsorption time,temperature,and initial concentration of copper ions on the adsorption process and removal efficiency.Besides the experimental results are analyzed with kinetic analysis and othermal adsorption model fitting.Though calculate the thermodynamic parameters and reevaluate the regeneration performance of the adsorbent material showing that the adsorption effect reach the best when the pH is 5,and the adsorption performance of the adsorbent is best when the adsorbent dosage is 1 g/L.Adsorption can reach equilibrium at 60 min under optimal adsorption conditions.The adsorption kinetics of modified polyacrylonitrile nanofiber membranes on copper ions is in accordance with the pseudo-second order kinetics reaction,and the adsorption isotherm is more in line with the Langmuir isotherm adsorption model.The thermodynamic parameter calculation results show that the adsorption reaction is an endothermic,entropy-increasing spontaneous process.Use 0.1 mol/L HNO3 solution as a desorption solution to study the reusability of the material.It is found that after four times adsorption-desorption cycles,the material still has high adsorption capacity and good recyclability. |
PDF Full Text Request