Preparation Poly(vinylimidazole)-based Microspheres And Study On Adsorption Properties Of Metal Ions

Aquatic plants and animals are the delicious food on the humankind menu from ancient time.With the rapid development of China's industry,agriculture and food manufacturing,water crisis has again sounded warnings in China because of co-existence of serious situation of water waste and pollution in urban areas.The water condition will seriously affect the living environment of aquatic animals and plants.Since heavy metal is easy to pass food chain but living things beneficiate,to living things and the human body,healthy graveness threatens formation.Therefore,it is necessary to take a repid,simple and economical method to remove harmful pollutants such as heavy metal ions.Adsorption method is one of the most common ways of heavy metal contamination.Polymer copolymers have gained more and more attention in the study of heavy metal adsorption due to their specific chemical nature and abundant surface functional groups.In this paper,polyethylene glycol dimethacrylate is used as a crosslinking agent,In order to obtain stable adsorbent and good adsorption performance,metal chelating agent is added in the process of synthesizing the adsorbent polymer.Utilizing the adsorbent's characteristics,polyacrylic acid microspheres can be used as an effective adsorbent to remove the food industrial waste water.The five different proportions of cross-linking agents are used to synthesize polyacrylic acid microspheres.The new polyacrylic acid microspheres have the advantages of spherical,uniform particle size,single good dispersion and large specific surface area.Various characterization methods are adopted to investigate property and microstructure of the blends of the adsorbent.This study is useful for forecasting copper and lead removal efficiency and helpful to the mechanism analysis of copper and lead adsorption on polyacrylic acid microspheres adsorbent.Then analyze the influence of environmental factors such as pH,adsorption time,initial concentration of adsorbent and reaction temperature on adsorption.An analysis of different adsorption isotherms and kinetic models were used show the reaction mechanism.The main findings are as follows:1.Polyethylene glycol dimethacrylate is used as a crosslinking agent,and in order to obtain stable adsorbent and good adsorption performance,metal chelating agent is added in the process of synthesizing the adsorbent polymer.According to scanning electron microscopy,the microspheres with a ratio of crosslinker to initiator of 2.0:0.8 have better morphology.The polyacrylic acid microspheres have a spherical shape,rough surface,and large specific surface area.The particle size is uniform and mostly distributed in the range of1.2-1.4 nm.The surface is rough and porous,have high specific surface area and a large number of contact sites,which is helpful for the absorption2.According to the data of Fourier transform infrared and XPS spectroscopy,the main mechanism of polyacrylic acid microspheres adsorbing heavy metals is that metal ions are complexed with oxygen-containing functional groups on the surface of microspheres.The Zeta potential shows that the surface of the synthesized nanospheres is positively charged,indicating that the effect of electrostatic interaction is negligible during the adsorption process.3.pH has a great influence on the adsorption of metal ions,because it not only affects the surface charge of the adsorbent,but also affects the degree and shape of ionization of metal ions in the solution.The adsorption capacity for copper ions increased at a high pH,reaching 83.21 mg g^-1.At low pH,the polyacrylic acid microspheres have low adsorption capacity for metal ions.The adsorption capacity for heavy metal ions in acidic pH solution is less than high pH.4 The adsorption of copper ions and lead ions by polyacrylic acid microspheres satisfies the Langmuir and Freundlich adsorption isotherms.The theoretical value obtained by the settlement is close to the actual value of the metal ions adsorption process,which means the adsorption process of the copper and lead is monolayer adsorption;the value of 1/n is between 0.36 and 0.68,so that the adsorption reaction of copper ions and lead ions can be completely removed.And the adsorption capacity of copper is greater than that of lead.5.The kinetic studies showd that the pseudo second-order rate equation can fit the adsorption of copper ions and lead ions data well.The initial reaction rate is fast and tends to equilibrate after 2 to 3 h.The reaction rate of the adsorption process is mainly controlled by chemical reaction.The adsorption rate coefficient?0.23?of lead is larger than the adsorption rate coefficient of copper?0.18?.6.Polyacrylic acid nanospheres have good adsorption properties for metal ions in aqueous solution,and the maximum adsorption capacity for copper and lead ions exceeds83.21 mg g^-1,compared with other adsorbent materials.It has large adsorption capacity and good practicability.