Preparation And Adsorption Characteristics Of The Lead Ion-imprinted Micro-beads

Lead is one of the heavy metal which has a serious hazard to human health, and harm tohuman health caused is irreversible. In daily life Lead hazards to humans mainly through airand water pollution, water pollution is one of the main reasons. All along, the enrichment andseparation of lead ions in the water environment is a research hotspot. Pb2+ions imprintedpolymer which was prepared by ion imprinting technology has good performance of specificadsorption with a very wide range of applications.In this paper, Pb2+imprinted polymer microspheres were prepared by emulsionsuspension polymerization. And polymer surface features, adsorption conditions, theadsorption characteristics and solid phase extraction performance were studied. The mainresearch includes:The methacrylic acid (MAA), EDMA and SDBS were used as functional monomer,crosslinker and dispersant respectively. The process affecting the polymer morphology, suchas the amounts of dispersant, the amounts of functional monomer, and the stirring rate, wereinvestigated in detail. After a series of experimental studies, to get the optimum amount ofeach substance: Pb(NO3)2,4.0mmol; MAA,12.0mmol; EDMA,8.0mL, Toluene,6.0mL;SDBS,0.8g; Span80,0.3mL; AIBN,0.2g; stirring rate,400r/min. Environmental scanningelection microscope(SEM) was used to analyze properties of the products. The adsorptionproperties and imprinting efficiency of IIPs were studied through batch tests with ultravioletspectrum, infrared spectrum.The adsorption characteristics of the lead ion-imprinted micro-beads were investigated indetail. The results showed that the lead ion-imprinted micro-beads were efficient for lead ionsremoval from aqueous solution in a broad pH range4-9. And the optimum pH is5. Effect oftemperature on the adsorption process was studied. Heat of adsorption, Gibbs free energy,entropy of adsorption was calculated according to the relationship of the thermodynamicfunction. Thermodynamics parameters depicted the exothermic nature of adsorption and theprocess is spontaneous and favorable. Experimental data were described by the pseudofirst-order mode1and the pseudo second-order mode1. The first-order model was agreed wel1on the adsorption of Pb2+on lead ion-imprinted micro-beads, and R2+=0.9893, adsorption rateconstant k2=0.5646.Selectivity and adsorption performance of the lead ion-imprinted micro-beads werestudied through the static adsorption experiment. Compared with non-ionic imprintedmicrospheres, lead ion-imprinted micro-beads have better recognition of Pb2+. The adsorption equilibrium was achieved in3h with a maximum adsorption capacity of15.29mg/g. In thepresence of competitive ions Cd2+, the static distribution coefficients and separation factorswere1616mL·g-1and19.01. The experimental data was measured linear fit by differentadsorption isotherm equation, the results show that the adsorption isotherm is more in linewith the Langmuir isotherm equation, the linear correlation coefficient is0.9989.Solid phase extraction column was prepared with lead ion-imprinted micro-beads as thefiller. The dynamic adsorption capacity measured from breakthrough curve is12.23mg·g-1, thetotal transfer mass coefficient is0.1680s-1, and the height of mass transfer zone is5.42cm.Provide a theoretical basis for the enrichment of lead ions in water. A series of experiments ofadsorption and elution were used to study the stability and of the solid phase extractioncolumn. The results showed that after six adsorption-elution processes, the dsorption rate ofnot less than95%, the solid phase extraction column have good stability and reuse under theexperimental conditions determined.