Preparation Of Novel Ion Imprinted Polymers And Their Application In The Determination Of Lead And Cadmium Ions

Heavy metal pollution poses a serious threat to the security of ecosystem and human health in China.Among them,lead and cadmium are highly toxic,persistent and accumulative,which can be enriched through food chain,causing damage to plants,animals and human body.Therefore,it is urgent to establish a sensitive,rapid,convenient and accurate technology to realize the real-time dynamic monitoring of trace lead and cadmium in the environment,investigate their migration law and deeply assess the health hazards caused by heavy metal pollution.The pretreatment of environmental samples is complex due to serious matrix interferences.The common chelation extraction method needs to consume a lot of solvent and the operation is complicated and time-consuming.In addition,the detection of heavy metals is still dependent on large and expensive analytical instruments,which cannot be used for fast,convenient,sensitive and accurate on-site analysis.Ion imprinted polymers are materials with specific recognition cavities made by chelating template ions with functional monomers and crosslinking.Because of their ability of specific recognition,they can specifically recognize and remove target ions in complex samples.However,the selective recognition ability of conventional ion imprinted polymers is not enough to meet the analysis needs of trace heavy metals in environmental samples due to the lack of specific functional groups of template ions.Based on this,this study aims to prepare two kinds of ion imprinted polymers for highly selective recognition of lead and cadmium ions and establish rapid detection methods taking advantage of convenient spectral analysis technology for the analysis of trace lead and cadmium ions in environmental samples.This study is divided into two parts:Part Ⅰ:Preparation of three-dimensional ion imprinted polymersand their application in the determination of lead ionsObjective:To prepare three-dimensional ion imprinted polymers for highly selective recognition of lead ions by film forming,swelling/folding and crosslinking process using environmentally friendly modified gelatin and chitosan as functional monomers,and establish a method for rapid detection of lead ions in environmental water samples.Methods:The 8-hydroxyquinoline-grafted gelatin was synthesized according to the Mannich reaction.Then 8-hydroxyquinoline-grafted gelatin and chitosan as monomers were mixed with lead acetate to form a hydrogel film.The film was subsequently swelled,folded and crosslinked with environmentally friendly Genipin to prepare three-dimensional ion imprinted polymers.The structure and morphology of the polymers were characterized by fourier transform-infrared spectroscopy,scanning electron microscopy,and thermogravimetric and differential scanning calorimetric analysis.The selective adsorption performances were evaluated by investigating adsorption capacity,adsorption kinetics and theoretical models.Finally,using the selective recognition ability of ion imprinted polymers and the spectroscopic changes of rhodamine B induced by catalytic effect of lead ions,a rapid detection technology was established for determination of trace lead ions.Results:Imprinted cavities were formed by 8-hydroxyquinoline-grafted gelatin and chitosan as monomers on three dimensional ion imprinted polymers.The polymers could reach equilibrium in 45 min and exhibited high adsorption capacity of 235.7 mg g^-1.The imprinted factor was 2.9.Under the optimized extraction conditions（pH=6,mass of adsorbents was 20 mg,washing volume was 2 mL,eluting volume was 1 mL）,the linear range was ranged from 1 ng mL^-1 to 100 ng mL^-1 with the limit of detection of 0.2 ng L^-1 and the recoveries were 96.6%¹04.3%,with RSD≤7.6%.The results were consistent with the results obtained from ICP-MS and the correlation coefficient was0.990.Conclusions:Environmentally friendly three-dimensional ion imprinted polymers with highly selective recognition of lead ions were prepared.Based on this,a rapid detection method was established,which make possible the rapid and supersensitive detection of lead ions in water.Part Ⅱ: Preparation of ion imprinted polymers-paper composites and their application in the determination of cadmium ions Objective: Taking advantages of rapid,convenient and low-cost paper analysis and the ability of highly selective recognition of ion imprinted polymers,this study aims to prepare ion imprinted polymers-paper composites with specific recognition of cadmium ions and establish a method for rapid analysis of cadmium ions in environmental water samples.Methods: In this study,a disposable paper was firstly silanized and then modified with initiator groups.Ion imprinted polymers-paper composites were synthesized using cadmium acetate as template,polyethyleneimine and methacrylic acid as monomers and ethyleneglycol dimethacrylate as cross-linker by reversible addition-fragmentation chain transfer radical polymerization.The structure and morphology of the polymers were characterized by fourier transform-infrared spectroscopy,scanning electron microscopy,and X-ray photoelectric spectroscopy.The selective adsorption performances were evaluated by investigating adsorption capacity,adsorption kinetics and theoretical models.Finally,using the selective recognition ability of ion imprinted polymers-paper composites and the color reaction induced by dithizone,a rapid detection technology was established to determine trace cadmium ions in water.Results: The imprinted cavities were formed by polyethyleneimine and methacrylic acid on the surface of ion imprinted polymers-paper composites which still maintained the three-dimensional structure of paper base.The composites could reach equilibrium in 45 min and exhibited high adsorption capacity of 155.2 mg g^-1.The imprinted factor was 3.1.Under the optimized extraction conditions（p H=7,sample volume was 10 m L,contact time was 6 min,washing time was 3 min）,the linear range was ranged from 1 ng m L^-1 to 100 ng m L^-1 with the limit of detection of 0.4 ng L^-1 and the recoveries were 97.5%^-109.3%,with RSD≤12.7%.The results were consistent with the results obtained from ICP-MS and the correlation coefficient was 0.9986.Conclusions: Ion imprinted polymers-paper composites with highly selective recognition of cadmium ions were prepared.Based on this,a rapid,convenient,sensitive and accurate detection method was established,which make possible the on-site analysis of cadmium ions in environmental water samples.