Research And Application Of Magnetic Cadmium Ion Imprinted Polymer

The rapid expansion of industrialization and urbanization in China has brought out enormous pressure to environment,and a series of problems from environmental pollution is getting more and more widespread attention.Among them,food poisoning incidents caused by heavy metal ions also occur from time to time.Cadmium and nickel are two common heavy metals in industrial production,and are also two unavoidable heavy metal ions in the wastewater of nickel cadmium battery industry.These two ions enter the organism from the environment,participate in the biosphere cycle,and eventually accumulate in the human body,bringing various diseases and safety hazards to human life and health.Therefore,the removal,recovery,and reuse of heavy metal ions such as Cd2+and Ni2+ ions in industrial wastewater have important practical significance for resource conservation and environmental protection.Among the numerous treatment methods currently developed,the adsorption method has been extensively studied and applied as a result of its good treatment effect,easy to use,recyclability of materials and low cost.At the same time,the development of imprinting technology has also provided an effective way to solve the problem of poor selectivity of general adsorbents.In this dissertation,cadmium and nickel ions used as templates and L-histidine as ligand,magnetic cadmium ion imprinted polymers and magnetic cadmium-nickel double ion imprinted polymers were synthesized via ion imprinting technology and their structure and adsorptive property were researched in detail.The main part of the experiments is as below:1.Manganese ferromagnetic(MnFe2O4)magnetic nanoparticles were synthesized by co-precipitation method.The magnetic dendritic mesoporous silicon matrix material(MDMS)was prepared by using the hydrolysis condensation of silicon reagents to coat a SiO2 layer on the surface of MnFe2O4.Subsequently,N-methylacryloyl-L-histidine(MAH)was synthesized as a ligand to form the MAH-Cd complex with cadmium ions.And the complex was further copolymerized with the monomer 4-vinylpyridine(4-VP)on the substrate surface to successfully prepare a magnetic macroporous silicon cadmium ion imprinted polymer(MDMS@MAH-Cd-IIP).Various characterization methods such as scanning electron microscopy(SEM)were used in the experiment to study the surface structure,group distribution,and crystal structure of the material.A magnetic measurement system and a surface area pore analyzer were used to evaluate the good magnetism and surface pore structure of the material.In addition,X-ray photoelectron spectroscopy(XPS)showed that imino nitrogen in 4-VP and the carboxyl oxygen and imino nitrogen in L-histidine were the most important coordination atoms of MDMS@MAH-Cd-IIP.2.Detailed study was conducted on the adsorption performance of the material MDMS@MAH-Cd-IIP for cadmium ions.The adsorption experiments of MDMS@MAH-Cd-IIP for Cd2+ showed that the maximum adsorption capacity at pH=6 and 25℃ was 21.04 mg·g-1,which was nearly 10 times than MDMS@MAH-CdNIP.The adsorption could be quickly finished within 35 minutes.The pseudo-secondorder kinetic model and Langmuir isotherm adsorption model suggested that Cd2+was adsorbed in a single molecular layer on the surface of the imprinted material with chemical adsorption as a rate control step.Selective experiments verified the high selectivity of the MDMS@MAH-Cd-IIP in a binary mixed solution of template ions coexisting with Zn2+,Pb2+,Co2+and Ni2+ions.Furthermore,the material was reused 5 times without significant loss of adsorption capacity.Lastly,the MDMS@MAH-CdIIP was used for the extraction of Cd2+ from actual water samples with the recovery of 90.0-102.0%,and the RSD was 3.34-8.23%,which demonstrated that it was an ideal material for adsorption and detection of Cd2+ from aqueous solution with excellent stability and repeatability.3.The magnetic matrix material(MCTS@GO)was synthesized based on laminated structure of GO and membrane properties of chitosan(CTS).Then,a new sandwich magnetic cadmium-nickel double ion imprinted polymer composite(MCTS@GO@DIIP)was synthesized using L-histidine as the ligand and glutaraldehyde as the crosslinking agent for the simultaneous removal of Cd2+and Ni2+ions from aqueous solutions.The microstructure,pore structure and surface chemical bond state of the materials were investigated by means of transmission electron microscope(TEM),N2 adsorption-desorption experiment,Fourier transform infrared spectroscopy(FT-IR)and other characterization methods,which verified the successful synthesis of the matrix material and the successful grafting of the double ion imprinted layer.The adsorption experiment results showed that MCTS@GO@DIIP achieved adsorption equilibrium for Cd2+and Ni2+ions in just 30 minutes,with maximum adsorption capacities of 39.35 and 33.91 mg·g-1,respectively.The adsorption process of Cd2+and Ni2+ions on the MCTS@GO@DIIP was agree with the pseudo-secondorder kinetic model and Langmuir isotherm adsorption model,proclaiming that the two ions were adsorbed in a single molecular layer while chemical adsorption was a speed control step.Moreover,the adsorption experiments verified that the proposed MCTS@GO@DIIP material had good selectivity and reusability.The MSPE with the materials for separation Cd2+ and Ni2+ ions in actual water samples had good recovery and reproducibility,which demonstrated its broad application prospect in environmental sample detection.Lastly,the X-ray photoelectron spectroscopy(XPS)experimental results indicated that the coordination of=N-and carboxyl oxygen in Lhistidine with Cd2+ and Ni2+ ions was the possible adsorption mechanism.