| Surface imprinting technique is a new strategy for selective removal or recycle of precious metal ions. It utilities the imprinted cavities which is formed on the adsorbent surface during the synthesis process, so the adsorbent has predetermination and specific recognition, it is a present research hot spot. The main contents of this research are preparing the prospective new ion imprinted material-poly(ethylenimine)-grafted silica gel adsorption material which used silica gel as matrix,γ-Chloropropyltrimethoxy silane (CPTMS) as coupling agent, poly(ethylenimine) (PAA) as functional monomer and epichlorohydrin (ECH) as a crosslinking agent and Cu2+as template ions. The synthesis conditions of CP-SiO2 and IIP-PAA/SiO2 are investigated, alkylation reaction, grafting reaction and surface ion imprinting process on the surface of silica are studied, and the material adsorption properties of heavy metal ions and the mechanism is discussed.To improve the stability of adsorbent acid, this study uses hydration in sealed and thermostatic vessels to improve synthesis process, and the prepared CP-SiO2 has excellent hydrolysis resistance. The alkylation reaction conditions optimized via single-factor experiment show that:adopting hydration improves the load and stability of the alkylated silica gel significiantly, the optimum hydration volume was 8%, the mass ratio of water and CPTMS mass is 1:15, y-chloropropyltrimethoxysilane level and quality of raw silica is 1:1 more or less, reaction time was 10 h, temperature was 353 K.PAA/SiO2 was synthesized by grafting reaction, and the amine content of its surface was 1.81 mmol·g-1. On this basis, a novel ion imprinted material IIP-PAA/SiO2 was prepared using Cu2+ion as the template, poly(ethylenimine) (PAA) on the surface of silica gel as functional monomer epichlorohydrin (ECH) as a crosslinking agent. The experimental factor is ascertained by orthogonal test, and the preparation conditions are optimized:the usage of adsorptive Cu2+ is 0.3 times of mole of atom N before imprinting, the usage of ECH crosslinking agent is 0.5 times of mole of atom N, reaction time is 3 h, reaction temperature is 323 K, the methanol is chosen as solvent, the template with SO42- has a better imprinting effect. TheⅡP-PAA/SiO2 has much better specific recognition in Cu2+and Zn2+solution. The selectivity coefficient of PAA/SiO2, NⅡP-PAA/SiO2 andⅡP-PAA/SiO2 to Cn2+are 3.88,3.40 and 86.60 respectively. At the same experimental conditions, the saturated adsorption capacity ofⅡP-PAA/SiO2 materials has also been significantly improved. There are two classes of binding points of PAA/SiO2 andⅡP-PAA/SiO2 by Scatchard curve analysis.The adsorption and recognition performances of PAA/SiO2 andⅡP-PAA/SiO2 were studied by static adsorption. The experiment results showed that the best pH value of Cu2+ was 4.0～5.0. Under the experimental conditions of the study, the adsorption of PAA/SiO2 andⅡP-PAA/SiO2 to Cu2+ is a single molecular layer of chemical adsorption, adsorption equilibrium data on Cu2+ is in accordance with Langmuir model, the adsorption capacity of PAA/SiO2 to Cu2+ is increased with temperature increasing, the adsorption capacity ofⅡP-PAA/SiO2 to Cu2+ is decreased with temperature increasing, after the measurement and calculation, the adsorption enthalpy, free energy and adsorption entropy of adsorption process could be calculated. Adsorption kinetic data can be described by the pseudo-second-order kinetic equation, and the fitting adsorption kinetic constants are related with the solution concentration.By using 0.1mol·L-1 hydrochloric acid as eluent, the absorbed Cu2+ ions are eluted easily fromⅡP-PAA/SiO2, and the adsorption capacity ofⅡP-PAA/SiO2 is stable after 5 times of repeated use. |
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