Research On The Adsorption Of Phenol And Its Derivatives On Hybrid Mesoporous Carbon/Silica Materials

Activated carbons (AC) and mesoporous silica are used as adsorbents. Thereare abundant functional groups on the surface of AC, Mesoporous silica haslarger pore size and pore volume, high surface area and ordered pore structure.So it is a good way to combine both advantages of AC and mesoporous silicafurther to synthesize hybrid mesoporous carbon/silica composites (C/MCM-41)with the properties of abundant functional groups on the surface of mesoporechannel and larger pore volume and pore size. Owing to those structuralproperties, it is beneficial to adsorb phenol and its derivatives.MCM-41was prepared by hydrothermal method and usedcetyltrimethylammonium bromide and tetraethoxysilane as surfactant and silicasource under alkaline conditions, respectively. C/MCM-41was prepared by hardtemplate method, and was prepared using directly carbonized surfactant in thechannel. The products were characterized by infrared spectroscopy, X-raydiffraction, Transmission electron microscope. It showed that the hybridmesoporous carbon/silica composites possessed uniform mesopores. Thetreatment of directly carbonized surfactant did not affect the hexagonal orderingof the parent silica. The carbon originated from the surfactant in the mesoporewas possibly existed in the form of a coating of the mesopores. Phenol wasselected as a model of pollutant in our studies. The adsorption properties ofphenol and its derivatives on C/MCM-41had been examined. The studies werecarried out under various experimental conditions such as adsorption time,temperature, pH, initial concentration, aged temperature and the kind ofadsorbent. These conditions had an obvious effect on the adsorption behavior. The equilibrium adsorption time was75min. Lower temperature was morefavourable for the adsorption of phenol. At pH=3, the surface of C/MCM-41waspositively charged and as there was no electrostatic repulsion between theunionized phenol species and the positively charged surface and thus adsorptioncapacity was higher. It showed a25%higher adsorption capacity of C/MCM-41compared to that of MCM-41. Furthermore, the maximum uptake ofhydroquinone on hybrid mesoporous carbon/silica composites was found to be1.31mmol/g. The result showed that the product had a good adsorption propertyin hydroquinone.The result data for phenol adsorption was analyzed by Freundlich andLangmuir model. However the Freundlich models fitted better than the Langmuirmodels. The kinetic models such as pseudo-first-order, pseudo-second-order andintraparticle diffusion models were selected to understand the mechanism ofadsorption. It showed that the R2of pseudo-second-order adsorption kinetics waslarger, so the result was fitted better to other adsorption kinetics.