Studies On Preparation Of Toxic Oxyacid Ion-imprinted Material And Its Ion Recognition And Combination Character

With the process of global industrialization, the water pollution problemsbecome more and more serious. Especially water pollution of some toxic oxyacid ionhas caused serious harm to human health and the ecological balance of the water body.Therefore, it is an urgent environmental governance issue that developing newtechnologies and materials to try to remove the toxic oxyacid ion from environment.In this work, chromate anion and molybdate anion surface-imprinted material wereprepared by using the novel ionic surface-imprinting technique, respectively. The ionrecognition and combination characters were examined in depth. The ionsurface-imprinted material has potential applications in removing the toxic oxyacidion from aqueous solutions and it would have great scientific significance forenvironmental protection.Firstly， the micro-sized silica gel particles were surface-modified with3-aminopropyltrimethoxysilane （AMPS） as coupling agent, which made aminogroups introduced onto the surfaces of silica gel particles, obtaining the modifiedparticles AMPS-SiO₂. The surface-initiated graft-polymerization of DMAEMA wasconducted in an aqueous solution by initiating the amino group/persulfate redoxsystem, obtaining the grafted particles PDMAEMA/SiO₂. The particles werecharacterized by several methods and the effects of the main factors on the polymerreaction processes were examined. The experimental results show that the aminogroup-persulfate initiation system can effectively initiate the graft-polymerization ofDMAEMA on silica gel particles. Under the suitable conditions such as at35℃and with an amount of1.0%（percent of monomer mass for persulfate）, the graftedparticles PDMAEMA/SiO₂with a grafting degree of24g/100g can be obtained.Subsequently, a quatemization reaction of the grafted PDMAEMA was carriedout by using epichlorohydrin as reagent. As a result, the quaternization transform ofthe grafted PDMAEMA was realized, obtaining the functional composite particlesQPDMAEMA/SiO₂. The particles were characterized with FTIR. The effects of themain factors on the quaternization reaction were examined. The experimental resultsshow that the quaternization degree of the functional particles QPDMAEMA/SiO₂can get up to65%with epichlorohydrin used as solvent and at60℃.The ion imprinting towards the functional macromolecules QPDMAEMA wasconducted with CrO₄^2-anion as the template ion and hexamethylenediamine ascrosslinker with the novel ionic surface-imprinting technique, and CrO₄^2-anionsurface-imprinted material IIP-QPDMAEMA/SiO₂was prepared. Both static anddynamic methods were adopted to study the binding properties and ion recognitioncharacter of IIP-QPDMAEMA/SiO₂for CrO₄^2-ion. The experimental results showthat this chromate anion-imprinted material has excellent recognition selectivity andcombination affinity for the template CrO₄^2-anion. Compared to the two contrastanions, NO3-and HPO₄^2-anions, the selectivity coefficients ofIIP-QPDMAEMA/SiO₂for CrO₄^2-anion can reach up to8.39and10.02, respectively,which displays very high ion recognition ability. The surface-imprinted materialIIP-QPDMAEMA/SiO₂has excellent elution property, the desorption ratio of CrO₄^2-ion reaches to97.6%in18BV with aqueous solution of NaCl（pH=10） as eluent,The MoO₄^2-anion imprinting towards the functional macromoleculesQPDMAEMA was conducted with1,6-hexanediamine as crosslinker and MoO₄^2-anion surface-imprinted material IIP-QPDMAEMA/SiO₂was obtained, namelyMoO₄^2-anion surface-imprinted material IIP-QPDMAEMA/SiO₂. Both static anddynamic methods were adopted to study the binding properties and ion recognitioncharacter of IIP-QPDMAEMA/SiO₂for MoO₄^2-ion. The experimental results show that this MoO₄^2-anion surface-imprinted material has specific recognition selectivityand combination affinity for the template ion MoO₄^2-anion. Relative to the twocontrast anions, WO₄^2-and MnO₄^-anions, the selectivity coefficients ofIIP-QPDMAEMA/SiO₂for MoO₄^2-anion were6.41and5.39, respectively, whichalso displays high ion recognition ability. The surface-imprinted materialIIP-QPDMAEMA/SiO₂has excellent elution property, the desorption ratio of MoO₄^2-ion reaches to98.04%in22BV with aqueous solution of NaCl（pH=10） as eluent.