| Recently, the haze and fog are found frequently in northern part of the country. The oxidized sulfur and nitrogen compounds contained in fuel oil are primary substances for causing this phenomenon. Dibenzothiophene (DBT) and indole are typical sulfur and nitrogen compounds in fuel oil, and the study for removal of them has been a hot in the air pollution control field. Meanwhile, industrial wastewater containing phenol is discharged casually from the ways of petroleum refining, coke making and petroleum and chemicals and so on. It leads to phenols pollution getting serious in some regions of country. As typical toxic substance in water environment, phenol has become the major control object in the water. The technology of adsorption and separation with characteristics of easy operation, low cost, high enrichment efficiency and no secondary pollution has been widely used to removal of sulfur and nitrogen from fuel oil and the deprivation process of phenol from waste water. However, the conventional adsorbents have some drawbacks, such as poor selectivity, low adsorption capacity and long adsorption equilibrium time.Molecular imprinting technology (MIT) is new method derived from imitation of the interaction between antibody and antigens. Molecularly imprinted polymers (MIPs) prepared by this way has specific recognition capacity to target molecule, so MIPs has been applied in the field of environment pollution control. However, few species of MIPs realize industrialization now, and most researches of MIPs are still in experimental stage. One of the most major reasons is that the preparation of MIPs was affected by many factors. It is difficult to choose the imprinting system, especially for template molecule with weak functional monomer.Molecular simulation using theoretical method and computing technology simulates microscopic behavior of molecular movement. Using the molecular simulation, the development cycle of new materials could be shortened and the cost could be deducted. In the MIT, in order to select the functional monomer which has strong interaction with template, the selected technique of molecular simulation and calculation has been concerned widely. But more qualitative study and less quantitative study were reported.Based on the background above, in our study, DBT, indole and phenol are chosen as templates,4-vinylpyridine (4VP), acrylamide (AAm) and methacrylic acid (MAA) as functional monomer. At first, molecular simulation software Gaussian09W is adopted to optimize and simulate the minimum energy conformation of template, monomer and compounds using Restricted Hartree-Fock (RHF) method and natural bond orbital (NBO) theory. At the same time, the NBO charge and corresponding binding energy of template, monomer and compounds are calculated. The mechanism of the interaction between template and monomer is forecasted. The suitable pre-assembled system of molecular imprinting is selected and used to aided design of MIPs.According to the above results of the molecular simulation, combined with atom transfer radical polymerization and MIT, three kinds of MIPs with the ability of specific recognition are prepared using phenol, DBT and indole as target molecules, respectively. Their structures and morphologies are also characterized. The influencing factors on the selective adsorption and separation to the template molecules, adsorption equilibrium and kinetics of these MIPs are then investigated. The results show that:(1) for the imprinting pre-assembly systems consisting of phenol and different monomers, the simulation results show that the bind energy and the molecular conformation between phenol and MAA are higher and more stable than4VP, AAm, respectively. And when the ratio is1:3between phenol and MAA, the simulation imprinting effect is the optimum. In the processes of preparing three kinds of MIPs, according to the above ratio, atom transfer radical polymerization using ferric trichloride/triphenylphosphine as catalytic system has been introduced to prepare4VP-MMIPs, AAm-MMIPs and MAA-MMIPs, respectively. Then the binding ratio, distribution coefficient and imprinting factor are compared. The results show that the above three indexes using MAA-MMIPs as the objects of study are0.616,1.281and7.440, respectively. The three indexes of MAA-MMIPs are all the highest in4VP-MMIPs, AAm-MMIPs and MAA-MMIPs, and it indicates that the imprinting effect of MAA-MMIPs is the best. This is attributed to stable specific binding sites between phenol and MAA and thin protective layer. The experimental results are the same as simulate results, the powerful experimental proof is offered to reliability and accuracy of molecular simulation applied in the field of molecular imprinting.(2) In the imprinting pre-assembled systems of DBT and functional monomers, the interaction energy between MAA and DBT is higher than other complexes, and the molecular conformation is the most stable. When the ratio is1:2between DBT and MAA, the simulation imprinting effect is the optimum. According to the simulation result, the silica-based and magnetic MIPs which have selective adsorption and recognition capacity to DBT are prepared by atom transfer radical polymerization (ATRP) with CuBr/2,2’-bpy and CuBr2/PMDET as catalytic systems on silica-based supporter and magnetic carrier, respectively. The results show that both two kinds of MIPs have superior surface property and thermal stability, et al. And the results of adsorption performance indicate that they have favorable selectivity and competitive adsorption towards DBT. The adsorption processes follow Elovich model by the kinetic analysis, and Sips equation is obeyed by the isothermal analysis.(3) In the imprinting pre-assembled systems of indole and functional monomers, the interaction energy between AAm and indole is higher than other complexes, and the molecular conformation is the most stable. When the ratio is1:4between indole and MAA, the simulation imprinting effect is the optimum. According to the simulation result, the silica-based and magnetic MIPs which can selectively adsorb and recognize indole are prepared by ATRP with CuBr/2,2’-bpy and FeCl3/triphenylphosphine as catalytic systems on silica-based supporter and magnetic carrier, respectively. The results show that both two kinds of MIPs have superior surface property and thermal stability. And the results of adsorption performance indicate that they have favorable selectivity and competitive adsorption towards indole. The adsorption processes respectively follow Elovich model and Langmuir equation by the kinetic analysis and isothermal analysis.According to the study of this paper, the pre-assembled system of computer-aided design MIPs towards phenol, DBT and indole is built initially. Meanwhile, the selectivity and recognition mechanism of MIPs is analyzed qualitatively and quantitatively. The study indicates that the recognition sites of MIPs are not only attributed to the interaction between templates and monomers, but also have intimate relationship with the spatial structure of imprinting pre-assembled system. For all templates and functional monomers discussed above, the more functional monomer is used, not means the better effect is occurred. The binging energy of complex formed by functional monomer and template exists between not only functional monomer and template, but also functional monomers. The MIPs we prepared have promising applications in environmental pollution and prevention. These are proved by the characterizations of structure and morphology, and tests of adsorption performance. |
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