Preparation And Performance Of Lead(?) Imprinted Chitosan/Alginate Complex Microspheres

Chitosan(CTS)and sodium alginate(SA)are the natural polymer materials which is cheap and easy to get.Because lead ions can be combined with CTS and SA by chemical bonds,CTS and SA can be applied to the adsorption of lead ions in aqueous solution.In this paper,lead(II)ion imprinted complex microspheres(Pb(II)-IIP)were prepared with CTS and SA as functional monomers,and the Pb(II)-IIP have good adsorption property for lead ions and good stability in aqueous solution.First,CTS/SA complex gel microspheres were prepared by stepwise method according to the previous experimental method,which was the best method of our laboratory.The preparation conditions were optimized by the response surface method using GA as cross-linked.The CTS/SA complex gel microspheres obtained at the optimized conditions showed 30.09 mg/g adsorption capacity for Pb2+ and 97.5%swelling degree in water.Secondly,the Pb(II)-IIP were prepared with lead(II)as the template ion based on the optimized stepwise method.The effects of GA amount and elution process on the adsorption capacity were investigated.The imprinted CTS/SA complex microspheres were in hydrogel state.FTIR analysis showed that there was an electrostatic effect between the COO" in SA and the NH3+ in CTS.Finally,the formation mechanism of lead ion imprinted CTS/SA complex gel microspheres was investigated.The effects of the initial concentration and the pH value of the adsorption solution on the adsorption capacity of the Pb(II)-IIP were investigated.The results showed that the proper initial concentration and pH value were 200 ug/ml and around 6,respectively.The adsorption of lead ions by Pb(II)-IIP was a spontaneous endothermic process.The adsorption kinetics agreed with the pseudo-second-order model.Intraparticle diffusion model showed there were four stages in the adsorption process.The first stage was controlled by the external diffusion.The second stage was controlled by the intraparticle diffusion.The third stage was controlled by the chemical adsorption and the fourth stage was balanced.The adsorption isotherm of the Pb(II)-IIP on Pb2+ was consistent with the Langmuir isothermal adsorption model.The imprinting factor was greater than 4.3,the separation factors for Cu2+ and Zn2+ were greater than 5 and 4,respectively.SEM showed that the Pb(II)-IIP had a well-developed porous structure and the imprinting process had influence on the surface morphology.TGA characterization showed that the imprinted polymer had good thermal stability.BET surface area analysis showed that the specific surface area of the imprinted gel microspheres was 5.99 m2/g,which was larger than that of the non-imprinted microspheres and contributed to the adsorption of lead ions.The theoretical largest adsorption was up to 208.3 mg/g.