Experimental And Molecular Simulation Study On The Preparation Of Ordered Mesoporous Carbons And Naphthalene Adsorption Performance

Polycyclic aromatic hydrocarbons (PAHs), known as one of the persistent organicpollutants, which have threatened people health and atmospheric environment seriously. Soit's very important to investigate how to remove PAHs effectively. In this work,naphthalene is taken as target pollutant of PAHs, and we investigated systematically thepreparation of ordered mesoporous carbons (OMCs) and the naphthalene adsorptionperformance by experiment and molecular simulation. The relatively detailed summaries wereas followed:OMCs with tunable pore sizes were synthesized by soft-template method, using F127astemplate, resol as carbon source, and boric acid and decane as pore-regulator agent. First ofall, the thermal polymerization temperature of resol and the molar ratio of phenol andformaldehyde are determined at80℃and1:3. The calcination was carried out in a tubularfurnace at450℃for2h and at900℃for3h under N2flow, the heating rate was1℃min^-1below450℃and5℃min-1above450℃. Then, the prepared samples were characterized byXRD, TEM, FT-IR and N2adsorption-desorption, the results showed that the OMCs have wellordered2D-hexagonal structures and the pore sizes are finely tunable from3.4to4.7nm byusing boric acid and from3.4nm to4.2nm by using decane as the pore-regulator agent.Actually, the synthesis mechanism of OMCs by soft template method is still in disputednow. In this thesis,computer simulation is applied to simulate the preparation process ofOMCs by dissipative particle dynamics (DPD) method in order to better understanding thepreparation mechanism from a macroscopic perspective. Firstly, all substances in the systemwere described successfully by Course-Grain model and the DPD interaction parameters weredefined by calculation. Secondly, we studied the self-assembly behavior of PEO_n-PPO_m-PEO_ntype triblock copolymer in solution. Thirdly, the effect of temperature and shearing rate onmicellar structures of F127were studied too. Fourthly, with the increasing of F127concentration, the micellar structure in F127/Ethanol system changed from sphere, cylinder,layer to cubic structure, respectively. Also, the introduction of resol did not change themicellar structure of F127in ethanol solution. The simulation results showed that thecylindrical micelle of F127was formed with hydrophobic core and hydrophilic corona aroundthe micelle interior, and resol surrounded the hydrophilic corona, which means F127acted asa structure-directing agent and played a key role in the precursor formation of OMCs, whichcorresponded with the experimental results. The naphthalene adsorption experiments on OMCs indicated that the OMCs have strongadsorption affinity to naphthalene and the maximum adsorption capacity was shown to reachup to303.2mg g-1. Furthermore, the mesopore volume between2³.5nm of OMCs wascrucial to the adsorption capacity and OMCs with pore sizes of2³.5nm were much morefavorable for the naphthalene adsorption process. The adsorption isotherms of naphthalene onOMCs match well with the Langmuir adsorption isotherm. Theoretical studies show that theadsorption kinetics of naphthalene on OMCs can be well accounted for using the Langmuiradsorption kinetics equation.We could draw some valuable conclusions by naphthalene adsorption experiments, butthe experiments could not tell us directly what the adsorption location and adsorption state areexactly on the surface of OMCs. Actually, we still don't know the microscopic structure ofOMCs very well because of the restriction of characterization technology, human factor andexperimental conditions. However, molecular simulation technology could make up thedisadvantages. In the work, grand canonical Monte Carlo (GCMC) method is applied tosimulate the naphthalene adsorption behavior on OMCs model. Firstly, the atomic structuremodel of OMCs was built by using molecular modeling technique, and then was characterizedby calculating the accessible solvent surface area, total pore volume, small-angle andwide-angle X-ray diffraction patterns. The observed steep adsorption increase in OMCs are oftype Langmuir IV with a clear H1-type hysteresis loop, this is characteristic of highly orderedmesoporous materials. And the naphthalene adsorption amount is105.4mg/g. Additionally,the adsorption heat is16.8Kcal/mol, which is less than20Kcal/mol and it means the process isphysical adsorption. Also, the adsorption rate rose with the increasing of pore size. Thesimulation results are proved and compared with corresponding experiment results.