Preparation Of Nanoflower Materials Induced By Silk Protein And Study Of Their Adsorption Properties For Heavy Metal Ion

With the development of society,the problem of water pollution is becoming more and more serious.For the treatment of heavy metal ions in sewage,the adsorption method has attracted widespread attention due to its simple operation and low cost.Nanoflower materials have showed great application prospects in the development of adsorbent materials due to their unique physical and chemical properties,such as good surface effects and size effects.In recent years,the use of environment-friendly natural macromolecules for efficient adsorption is an important research aspect.Silk protein(SF)molecules have attracted wide interest because of their wide sources,biocompatibility and biodegradability.In this thesis,novel nanoflower particle adsorbent and nanoflower composite adsorption membrane were prepared by using silk protein(SF)as the raw materials through organic-inorganic hybridization.The structure and composition of these two adsorption materials were characterized,and the adsorption performance of heavy metal ions were investigated.The main research contents of the paper are as follows:(1)Using natural silk fibroin protein SF as a raw material,protein-inorganic hybrid nanoflower particles(SF@Cu-NFs)were prepared by self-assembly method and applied to the efficient adsorption of heavy metal ions(Pb2+).The effects of silk protein,synthesis time,and silk protein concentration on the formation of SF@Cu-NFs were studied.Through a series of characterization methods(such as SEM,EDX,LSCM,XRD,FT-IR,and TGA,etc.),micromorphology research and structural analysis of SF@Cu-NFs were performed.SEM results showed that the prepared SF@Cu-NFs had dense and ordered three-dimensional structures,showing the shape of peony flowers;the experimental parameters such as pH,initial ion concentration,adsorption time,and adsorption temperature were investigated for the adsorption of SF@Cu-NFs on Pb2+;the effects of SF@Cu-HNFs on Pb2+ were systematically analyzed through the study of adsorption thermodynamics and adsorption kinetics.With excellent fitting by Langmuir model and pseudo-second-order kinetic model,the results indicated that the adsorption of Pb2+ was single-layer on SF@Cu-NFs with an adsorption capacity of up to 2500 mg g-1.The adsorption of Pb2+ by SF@Cu-NFs was a spontaneous exothermic process.However,high temperatures were disadvantageous to the removal of Pb2+ by SF@CuNFs.According to the adsorption mechanism of SF@Cu-NFs on Pb2+,based on the difference between organic and inorganic components,it was divided into two phases:fast adsorption and slow adsorption.Among them,the stamen of the nanoflower(SF as organic component)was considered as the main adsorption site for fast adsorption.This adsorption was caused by the multiple synergy between Pb2+ and the abundant N and O elements on the SF amide group.The petal(Cu3(PO4)2 crystal as inorganic component)was considered as the main adsorption site for slow adsorption.This adsorption was caused by the special synergy between Pb2+ and O element.The FT-IR spectrum,the particle internal diffusion model of Pb2+adsorbed by SF@Cu-NFs and the zeta potential measurement on the surface were used to further verify the two-stage adsorption process.(2)Using natural silk fibroin protein SF as a raw material,the protein-inorganic hybrid polyacid-modified nanocomposite membrane(TA/P VA/SF@Cu-NF s membrane)was prepared by a casting method and applied to highly efficient adsorption of heavy metal ions(Pb2+).The effects of the concentrations of polyvinyl alcohol and tannic acid on the formation of TA/PVA/SF@Cu-NFs membrane were studied.Through a series of characterization methods(such as SEM,EDX,FT-IR,etc.),micromorphology research and structural analysis of TA/PVA/SF@Cu-NFs membrane were carried out.SEM results showed that the prepared TA/PVA/SF@Cu-NFs membrane had SF@Cu-NFs flower-like particles with uniform dispersion and complete structure.Compared with the PVA membrane,the TA/PVA/SF@Cu-NFs membrane had a loose internal structure and a large specific surface area,which could be used for the adsorption treatment of substances.The experimental parameters such as pH,initial ion concentrations and adsorption time were examined for the adsorption of TA/P VA/SF@Cu-NF s membrane on Pb2+;the adsorption performance of TA/PVA/SF@Cu-NFs membrane for Pb2+ was systematically analyzed through adsorption isotherms and adsorption kinetics studies.With excellent fitting by Langmuir model and pseudo-second-order kinetic model,the results indicated that the adsorption of Pb2+ was single-layer on TA/PVA/SF@Cu-NFs membrane with an adsorption capacity of up to 55.10 mg g-1.According to the adsorption mechanism of TA/PVA/SF@Cu-NFs membrane on Pb2+,it could be divided into two stages:fast adsorption and slow adsorption.Among them,Pb2+passed through the boundary layer of the TA/PVA/SF@Cu-NFs membrane,and the tannic acid on the surface of the TA/PVA/SF@Cu-NFs membrane acted as a metal chelator to quickly adsorb Pb2+(fast adsorption).Then Pb2+ entered the membrane through the boundary layer of the TA/PVA/SF@Cu-NFs membrane,and was further adsorbed with the SF@Cu-NFs in the adsorption membrane(slow adsorption).The zeta potential measurement and the particle internal diffusion model of Pb2+adsorbed by TA/PVA/SF@Cu-NFs membrane further verified the two stages of the adsorption process.