| The selective enrichment and separation of metal ions is an important research in the field of chemistry, compared with the traditional techniques, combining molecular imprinting with membrane separation and preparing metal-ion imprinted membrane, which has effect on the selective adsorption and recognition of target metal ions, has the wide prospect on research and development.Aiming at the issue of silver selective enrichment and separation in waste solutions containing silver, silver-ion imprinted chitosan membrane Ag(â… )-â…¡M1 and silver-ion imprinted chitosan/polyvinyl alcohol blend membrane Ag(â… )-â…¡M2 were prepared by using Ag(â… ) as template, chitosan and chitosan/polyvinyl alcohol blend as functional materials respectively in aqueous solution in this work. The adsorption properties of these two membranes to Ag(â… ) and the effects including amount of imprinted ions, eluent, adsorption time, Ag(â… ) initial concentration and pH value of solution on adsorption capacity of silver-ion imprinted membrane were investigated. The mechanisms of recognition and binding between Ag(â… ) and active groups were preliminary explored by FI-IR and UV, the morphology of membrane were characterized by SEM and AFM, and the properties of physics and chemistry, selective adsorption and recycling performance of membrane were investigated meanwhile.The research shows that the atoms of N and O in CTS and PVA may get into the outer orbits of Ag(â… ), combine with each other according to metal coordination bond and form stable complex. The adsorption capacities of Ag(â… )-â…¡M1 and Ag(â… )-â…¡M2 to Ag(â… ) rise with growing adsorption time and Ag(â… ) initial concentration, the former saturated adsorption capacity was 14.02 mmol·g-1, and the latter was 22.21 mmol·g-1. At the same adsorption time and Ag(â… ) initial concentration, the former adsorption rate was 57.94%, and the latter was 66.08%. It can be seen after blending modification, Ag(â… )-â…¡M2 has better performance on adsorption properties.The optimum condition was determined by orthogonal experiment to prepare Ag(â… )-â…¡M2 with higher adsorption capacity:V(CTS)/V(PVA)=4 mL/6 mL, V(AgNO3) = 1.2 mL, V(cross linker)=0.8 mL, w(NaOH)=1.0%, and the adsorption capacity can reach up to 21.41 mmol·g-1. Ag(â… )-â…¡M2 with better performance on strength, toughness and adsorption capacity was prepared by heat-treated when controlling the temperature of 70℃and time of 30 minutes, and can be stripped completely in toughness and strength to some extent by lower concentration of NaOH solution, which was no effect on combination between Ag(â… ) and functional monomers. The elution rate of Ag(â… ) can reach up to 70.83% through direct and indirect assessments by using Na2S2O3 as eluent for 4 hours'elution. The glass transition temperature of Ag(â… )-â…¡M2 detected by DSC was 77.85℃, and the thermal stability decreases comparing with CTS/PVA blends while the polymers have the good performance on blend compatibility. It is obvious to observe by electrical microscope that the morphology of membrane present uneven fluctuations when Ag(â… ) was added while uniform and regular pores when Ag(â… ) was eluted.The hydrophilicity and swelling ratio of Ag(â… )-â…¡M2 were 164.03% and 77.78%, which were beneficial for enrichment and separation of Ag(â… ) in solution. Ag(â… )-â…¡M2 has the properties of priority, specificity and selectivity to adsorb and recognize Ag(â… ), and can be used in waste solution when interfering ions existed. Furthermore, Ag(â… )-â…¡M2 has the good performance on chemical stability and recycling, and can be worked as a favorable hydrophilic imprinted material.
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