Preparation And Properties Of Chromium Ion (Ⅵ) Imprinted Composite Membrane

Chromium ion（Ⅵ）has been widely concerned in the field of water pollution treatment because of its high toxicity and difficult separation.However,most of the conventional separation methods have the problems of low efficiency,high cost,low selectivity or easy to cause secondary pollution,and water pollution aggravates the lack of water resources.Therefore,it is urgent to find a highly selective adsorption and separation material for chromium ion（Ⅵ）.As an important branch of molecular imprinting technology,metal ion imprinting technology has been widely used in the separation and enrichment of chromium ion（Ⅵ）due to its advantages of high efficiency,high selectivity and low cost.However,conventional ion imprinted polymers were easy to destroy the imprinted sites in the preparation process of grinding and screening.The metal ion imprinted membranes were a new technology formed by the combination of metal ion imprinting technology and membrane separation technology,which can successfully solve the above problems.In this paper,based on metal ion imprinting technology,two kinds of chromium ion（Ⅵ）imprinted composite membranes and corresponding non imprinted composite membranes were prepared,and their properties were investigated.The main research includes the following two aspects:1.The chromium ion（Ⅵ）imprinted composite membranes and the corresponding non imprinted composite membranes were prepared by using the functional monomers commonly used in the laboratory.The preparation conditions of chromium ion（Ⅵ）imprinted composite membranes were studied by single factor experimental optimization,The results show that:under better conditions,the imprinting factor of chromium ion（Ⅵ）imprinted composite membrane was 2.40,and the adsorption equilibrium time for chromium ion（Ⅵ）was 60 min,and the saturated adsorption capacity was 34.60μmol/g;The adsorption behavior of chromium ion（Ⅵ）on the optimized ion imprinted composite membrane was in accordance with Langmuir isotherm and second-order kinetics model,and belongs to chemical adsorption;In the presence of"competitive ions",the best ion imprinted composite membrane has better permeation selectivity for chromium ion（Ⅵ）,and the separation process conforms to the"gate"model of piletsky.2.In this paper,29 chromium ion（Ⅵ）imprinted composite membranes(Cr（Ⅵ）-IICM_1-29)and corresponding non imprinted composite membranes(NICM_1-29)were prepared by surface grafting method with N,N’-（ethane-1,2-diyl）bis（2-methylacrylamide）（EBMA）as a new functional monomer.After systematic optimization of the preparation conditions of the imprinted composite membranes,the better synthesis conditions of the imprinted composite membranes were determined.The adsorption equilibrium time of chromium ion（Ⅵ）in solution was 45 min,the saturated adsorption capacity was 62.99μmol/g,and the imprinting factor was 2.58for the chromium ion（Ⅵ）imprinted composite membrane prepared under the better experimental conditions.The adsorption process of the better ion-imprinted composite membrane(Cr（Ⅵ）-IICM₁₃)for chromium ion（Ⅵ）is an entropy-driven spontaneous exothermic reaction,which follows the second-order kinetic equation and Freundlich adsorption equation.In the presence of"competing ions",Cr（Ⅵ）-IICM₁₃ has good permeability selectivity for chromium ion（Ⅵ）,and the separation process is combined with Piletsky’s"gate"model.The results show that:in a complex mixed system,the chromium ion（Ⅵ）imprinted composite membrane prepared with EBMA synthesized as a new functional monomer was compared with the chromium ion（Ⅵ）imprinted composite membrane prepared with commonly used functional monomer.The former has better permeation selectivity and higher affinity for template ion,which shows that the new compound designed and synthesized can be used as functional monomers,which also verifies the rationality of functional monomer design and enriches functional monomers.At the same time,it also provides a broad application prospect for the removal of chromium ion（Ⅵ）in sewage.