The Preparation And Application Of Molecularly Imprinted Polymers

Molecularly imprinted polymers were widely used in various fields due to their specific recognition and predetermined structure. Here, the imprinted polymers of CrO₄^2-, salicylic acid and sunset yellow were successfully prepared with [2-（methacryloyloxy） ethyl] trimethylammonium chloride （DMC） as functional monomer, and their adsorption performance was studied in detail. The main content of this paper was as following:（1） Introduction. The development, principle, classify, preparation method and application of molecularly imprinted polymers and nano-materials were summarized.（2） CrO₄^2- imprinted polymer (CrO₄^2-IIP) was prepared with CrO₄^2- as template ion, DMC and acrylamide （AM） as bio-functional monomer, N,N-methylenebisacrylamide （MBA） as cross-linking agent. The composition and morphology of CrO₄^2--IIP were characterized by Fourier transform infrared spectroscopy （FT-IR） and scanning electron microscope （SEM）. The adsorption thermodynamics, kinetics, and adsorptive selectivity of CrO₄^2--IIP for CrO₄^2- were investigated. It was found that the adsorption capacity reached maximum after 5 min at pH 4.0, and the maximum adsorption capacity was 108.7 mg/g. The quantitative desorption was achieved after 10 min by using 5.0 mL 0.5 mol/L H2SO4. The relative selectivity coefficients （k’） of CrO₄^2--IIP for PO43- and NO3- were 7.57 and 6.82, respectively. A method for determination of CrO₄^2- in tap water and electroplating wastewater by spectrophotometry after preconcentration with CrO₄^2--IIP was established. The linear range was 1.0-10.0 μg/L.（3） Salicylic acid molecularly imprinted polymer （SA-MIP） was prepared with salicylic acid as template, DMC as functional monomer and MBA as cross-linking agent. The molar ratio of salicylic acid, DMC and MBA in the preparation process was optimized. SA-MIP was characterized by FT-IR and SEM. The adsorption capacity reached maximum after 5 min at pH 7.0, and the maximum adsorption capacity was 206.1 mg/g. The complete desorption was achieved after 10 min by using 5.0 mL 0.5 mol/L HCl-ethanol solution （V/V,1:1）. Adsorption of SA-MIP for salicylic acid was multilayer adsorption, and adsorption rate was controlled by chemical adsorption. A method for determination of salicylic acid in human urine and medicine was established by fluorescence spectrophotometry after preconcentration with SA-MIP. The linear range was 0.01-0.5 mg/L.（4） Sunset yellow molecularly imprinted polymer nano-particles （SY-MIP NPs） were synthesized with sunset yellow as template molecule, DMC as functional monomer and ethylene glycol dimethacrylate （EDMA） as cross-linking agent. SA-MIP NPs were characterized by FT-IR, SEM, transmission electron microscopy （TEM）, and their specific surface area and thermal stability were measured, SY-MIP NPs had high adsorption capacity in wide pH range （pH 1.0-8.0） for sunset yellow. The maximum adsorption capacity of SA-MIP NPs was 144.6 mg/g. The adsorption equilibrium only needed five minutes. The quantitative desorption was very fast （1 min） by using 10.0 mgl/L HCl as the eluant The isotherm and kinetic of the adsorption were well consistent with Langmuir adsorption model and pseudo-second-order kinetic model, respectively. The relative selectivity coefficients of SY-MIP NPs for tartrazine and carmine were 9.76 and 12.6, respectively. SY-MIP NPs were regenerated for 10 times without significant absorption capacity decrease. The enrichment factor of SY-MIP NPs was 200.