Preparation And Adsorption Properties Of Molecularly Imprinted Polymers On The Surface Of Silica

Antibiotics sulfamethoxazole?SMX?and perfluorooctane carboxylic acid?PFOA?,perfluorooctane sulfonate?PFOS?have attracted much attention as emerging environmental pollutants.For the perspective of selective separation and enrichment of these two kinds of pollutants in wastewater,two kinds of surface molecularly imprinted polymers were prepared respectively by using SMX as template molecule,PFOS and PFOA as double template moleculesThe MIP?mesoporous-SiO₂?were prepared by thermal initiation in methanol solution using SMX as template molecule,MAA as functional monomer,EGDMA as crosslinking agent,AIBN as initiator and mesoporous SiO₂ spheres as carriers.The MIP?mesoporous-SiO₂?was characterized by scanning electron microscopy?SEM?,X-ray energy dispersive spectroscopy?EDS?,transmission electron microscopy?TEM?,Fourier transform infrared spectroscopy?FT-IR?,N₂ adsorption-desorption and thermogravimetry?TG?.The adsorption performance and specific recognition of SMX on MIP?mesoporous-SiO₂?were also studied.The results showed that the optimum preparation conditions of MIP?mesoporous-SiO₂?were as follows:the molar ratio of SMX:MAA:EGDMA was 1:4:10,the amount of carrier mesoporous SiO₂ was 0.15 g,the reaction temperature was 60?and the reaction time was 24 h.The adsorption capacity of MIP?mesoporous-SiO₂?for SMX decreased with the increase of pH.The adsorption adsorption isotherm can be well fitted by the Langmuir model,indicting that the adsorption of MIP?mesoporous-SiO₂?to SMX was monomolecular layer adsorptio.The adsorption rate was very fast and the adsorption equilibrium time was only 60min.The experimental data can be fitted by pseudo-second-order kinetic model,which indicating that the chemical adsorption was the adsorption rate control steps.The MIP?mesoporous-SiO₂?has good specific recognition ability to SMX in aqueous solution.The imprinting factor of MIP?mesoporous-SiO₂?was1.983,and the selectivity coefficients of structural analogues STZ and SMD were 1.298and 1.777,respectively.The MIP?mesoporous-SiO₂?can be effectively separated and selectively enrich SMX from water.Under the same conditions,the specific surface area,the maximum adsorption capacity and the specificity of MIP?mesoporous-SiO₂?were higher than those of MIP?nano-SiO₂?prepared by using nano-SiO₂ as the carrier.The MIP of double template were prepared by thermal polymerization in methanol solution using PFOA and PFOS as double template molecule,MAA as functional monomer,EGDMA as crosslinking agent,AIBN as initiator and KH-570 modified SiO₂ nanospheres as carrier.The polymers were characterized by SEM,FT-IR,TG,N₂ adsorption-desorption and their adsorption performance and specific recognition ability to PFOA and PFOS were studied.The results showed that the preparation conditions of the double template MIP were as follows:the molar ratio of PFOA:PFOS was 3:7,the molar ratio of the template molecule:functional monomer?AM?:crosslinking agent was 1:8:15,the amount of modified SiO₂ nanospheres was 0.1 g under the condition of AIBN as initiator,protection with nitrogen with the constant temperature 60?for 30 h.The adsorption capacity of double template MIP to PFOA and PFOS decreased with the increase of pH,and the adsorption isotherm could be fitted by Langmuir and Freundlich model which suggesting that the adsorption between MIP and double template moleculars was monomolecular layer adsorption.The adsorption rate of PFOA and PFOS was faster,and the adsorption equilibrium was achieved in 40min.The experimental datas of adsorption rate can be well fitted by pseudo-second order kinetic model.The dual template MIP had good specific recognition ability for PFOA and PFOS,and the imprinting factors were 1.996 and 2.780,respectively.The selectivity coefficients of PFOA relative to the structural analogs 2,4-D and SDBS were 1.569 and 1.196,respectively.And the selectivity coefficients of PFOS relative to the structural analogs 2,4-D and SDBS were 2.186 and 1.666,respectively.