Preparation Process Optimization And Preliminary Adsorption Investigation Of Surface Molecularly Imprinted Carbon Microsphere With Dibenzothiophene As Template

The demands of deep desulfurization from oils are more and more focused all over the world for the environmental protection. The surface molecular imprinting technique is an emerging separation way in that the template imprints on the surface of matrix, and, after removed, creats molecular cavities which are complementary to the template in size, shape and spatial arrangement of functional groups, and correspondingly able to improve the binding rate between recognition sites and imprinted molecules and the adsorption efficiency of the molecularly imprinted materials. In this paper, carbon microspheres (CMSs) which have large surface area, good mechanical and thermal stabilities, were used as the matrix and modified by oxidation, silinization, functional monomer grafting, and crosslinking, for the preparation of the imprinted materials for deep desulfurization.CMSs synthesized by chemical vapor deposition were oxidized by mixture acids (HNO3+H2SO4), then oxygen-containing groups were introduced onto the surface of CMSs. By virtue of the active sites on CMSs, KH-570 with double bonds was grafted onto the surface of CMSs. After coupling process, poly (2-arylamide-2-methyl propane sulfonic acid) (AMPS) was grafted onto the surface of silanized CMSs. Afterwards, the molecular imprinting was carried out towards the macromolecule PAMPS grafted on the surface of CMSs using DBT as template and ethylene dimethacrylate (EDMA) as crosslinking agent via the intermolecular hydrogen bond and electrostatic interaction. Subsequently, DBT imprinted material MIP-PAMPS/CMSs was obtained. The combining characteristic of MIP-PAMPS/CMSs for DBT was studied preliminarily with static and dynamic adsoption methods. The morphologies and microstructures of all samples were characterized by Fourier transformation infrared spectrometry, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry and atomic force microscopy. The results are as follows:1. Synergic effects between UV irradiation and inorganic acids oxidized CMSs efficiently, and oxygen-containing groups were introduced onto the surface of CMSs. UV/H2O2+H2SO4 showed the most amounts of oxygen-containing groups. It was a rapid and green method to oxidize carbon materials, although it was a little less effective than traditional oxidization.2. By the dehydration of the-OH groups of the CMSs and the-OCH3 groups of KH-570, double bonds were introduced onto the suface of CMSs. The effects of reaction time, KH-570 content and the ratio of ethanol to water on silanization were discussed and the optimum parameters were:1.0 mL of KH-570/0.3g of oxidized CMSs, reaction time of 2 h at 65℃, pH≈5, ethanol=45 mL, water=15 mL. The dispersion of silanized CMSs in ethanol was improved. This contributed to the enhanced compatibility of CMSs with various monomers.3. Based on the silanized CMSs,2-Acrylamido-2-methylpropanesulfonic acid (AMPS) was then grafted on the surface of cabon microspheres (CMSs) to prepare molecularly imprinted polymer for adsorbing dibenzothiophene. The conditions of grafting polymerization were optimized for four parameters, including reaction time, temperature and the content of AMPS and initiator. The results show that the preferable reaction temperature and time, the content of initiator and AMPS (AMPS/0.2 g silanied-CMSs) were 70℃,12 h,0.03 g and 1.0 g, respectively, in 20 mL of deionized water. The particles of PAMPS/CMSs were expected to be used in adsorbtion and sewage treatment.4. MIP-PAMPS/CMSs for adsorbing DBT were prepared, and the static and dynamic adsorption experiments were conducted preliminarily. DBT solutions in n-hexane with different concentrations were scanned to obtain UV spectra, and corresponding standard curves were obtained. Owing to the unfilterable impure particles which caused the enhancement of absorbance, abnormal results were observed in static method. Furthermore, this phenomenoa proved the fluorescent quantum dots of CMSs. An efficient method was required to examine the concentration of DBT. In dynamic experiment, MIP-PAMPS/CMSs and NIP-PAMPS/CMSs were compared with 1 mmol/L DBT to study the rapid adsorption. When 1 mL DBT was added into MIP-PAMPS/CMSs, the content of DBT decreased significantly from 279 to 20 ppm. MIP-PAMPS/CMSs (0.1 g) were saturated after 3×10-3 mmol of DBT were added and adsorpted 1.38×10-3 mmol of DBT, and the adsorption efficiency reached to 46%; NIP-PAMPS/CMSs (0.1 g) were saturated after 1×10-3 mmol of DBT were added and adsorpted only 1.66×10-4 mmol of DBT. The results show that the MIP-PAMPS/CMSs had a better selectivity for DBT than NIP-PAMPS/CMSs, and be promising to decrease the amount of DBT from oils.