| Aromatic organic compounds,which would lead to serious environmental problems with small amounts,are toxic and carcinogenic,so the removal of such organic pollutants has become increasingly important.The removal of organic pollutants by appropriate adsorbents is the most commonly used practices.Aerogels have been widely studied because of their large specific surface area.However,there were still having some disadvantages,such as small adsorption capacity and difficulty of separating it from water.Aerogel microspheres have a promising future of large specific surface area and good mobility.In addition,their nature of easy removal from water would make it not cause secondary pollution to the environment.In this paper,with silica sol selected as the raw materials,silica aerogel microspheres was prepared by using W/O emulsion method combing with the sol-gel process.On the basis of this process,carbon nanotube/silica composite aerogel microspheres(CS-CAMs)and graphene/silica composite aerogel microspheres(GS-CAMs)were synthesized by adding above corresponding carbon sources(carbon nanotubes(CNTs-COOH),graphite oxide(GO))to the silica sol,then combined with washing,solvent replacement,surface modification,vacuum drying,and high temperature treatment step,sequentially.Through assessing the results of the bulk density,N2 adsorption-desorption,etc.,the optimal ratio of CS-CAMs and GS-CAMs were obtained,and the adsorption capacity of toluene and phenol in aqueous were comparative studied with carbon nanotubes(CNTs),graphite(G),and SiO2 aerogel microspheres.The adsorption performance of the composite aerogel microspheres for different concentrations of toluene and phenol in aqueous solution at different temperatures was also studied,and the mechanism was discussed from the adsorption thermodynamics and adsorption kinetics.The results show that loose bu.k density of silica aerogel microspheres is 270 kg/m3,specific surface area and average pore diameter are 286 m2/g and 16.24 nm,respectively.The maximum saturated adsorption capacity of silica aerogel microspheres for different concentrations of toluene and phenol in aqueous solution at different temperatures are 181 mg/g and 137 mg/g,respectively.CS-CAMs was prepared by doping with different content of CNTs-COOH.When the doping content is 0.4%,the composite aerogel microspheres were spherical,uniform in size,and the overall performance was improved significantly.The loose bulk density of 0.4%CS-CAMs is 320 kg/m3,the specific surface area and average pore diameter are 321 m2/g,38.56 nm respectively.Compared with pure SiO2 aerogel microspheres,the specific surface area and pore size of CS-CAMs was even better.And its maximum saturation adsorption capacity for different concentration of toluene and phenol in aqueous solution at different temperatures were 214 mg/g and 171 mg/g,which are 1.2 times to the SiO2 aerogel microspheres,and about 1.4 and 1.3 times to the CNTs,respectively.GS-CAMs was prepared by doping with different content of GO.When the doping content is 0.4%,the properties of composite aerogel microspheres have significantly improved.The loose bulk density of 0.4%GS-CAMs is 300 kg/m3,the specific surface area and average pore diameter are 328 m2/g,31.23 nm respectively.Compared to the specific surface area and pore size of the pure SiO2 aerogel microspheres,it is increased significantly.And its maximum saturation adsorption capacity for different concentration of toluene and phenol in aqueous solution at different temperatures were 211 mg/g and 171 mg/g,which are 1.2 times to the SiO2 aerogel microspheres,and about 1.6 and 1.3 times to the G,respectively.The adsorption capacity of composite aerogel microspheres for toluene and phenol was mainly determined by the ?-? conjugation between adsorbate and adsorbent.The adsorption process was in accordance with the Freundlich isothermal adsorption model and the pseudo-second order model.The adsorption of toluene and phenol in aqueous solution is a spontaneous exothermic process. |
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