| Mesoporous carbon (MPC) is a kind of carbonaceous material with high content of 2-50 nm pores, and thus be very promising for the applications in selective adsorption of macromolecules because of high specific surface area, relative large and high orderly pore, high capacity and rate of adsorption, etc. Some conventional methods have been proposed for the preparation of MPC, including activation method, polymeration carbonization and template method, in which the template method aroused much more interests of research due to the easy control and regular structure of template-synthesized MPCs, but some shortages of template method especially high cost of template and less tunable structure of MPCs present some serious drawback for the popular utilization of template method in preparing MPCs. On the other hand, MPC adsorbent had to be re-activated by carbonization or other ways once the adsorbent reaches to its limit of adsorption process.In order to resolve the technical problems mentioned above, a feasible way is proposed in this work to prepare ZnO/MPC composite in low cost by making use of preliminarily-prepared Zn(OH)2 tiny particles as the template, and phenolic resin as the carbon precursor. The preparation processes involve homogeneous precipitation, resin impregnation, heating solidification, high-temperature carbonization and water-soaking purification. Phase analysis indicated that during the carbonization process at high temperature, Zn(OH)2 dehydrated into ZnO with a hexagonal wurtzite structure, which the water-soaking process effectively removed the soluble salt in the composite products. Pore diameter distribution determined by N2 adsorption showed the existence of abundant mesoscaled pored in the ZnO/MPC composite due to the volume change of Zn-containing particles and the removal of soluble salt. It can be observed under SEM that ZnO particles evenly embedded in the matrix of pyrolytic carbons, and a large amount of mesopores are left due to the washing out of the soluble salt. The result of thermogravimetric analysis demostrates that the mass ratio of ZnO and pyrolytic carbon in the as-prepared composite was about 2:3.In this work, the mixing program and NaOH content were regulated separately to realize a tunable control of the structure of ZnO/MPC composite, which was subsequently employed to remove methylene blue (MB), an azo dye, from its aqueous solution. The experimental results show that under the irradiation of ultraviolet light, the ZnO/MPC composite behaved an enhanced and sustainable ability of dye removal in comparison to that performed under natural light or dark atmosphere. The phenomena should be attributed to the effect of photocatalytic oxidation aroused by ZnO particles, which resulted in the degradation of MB dye under the stimulation of ultraviolet light and thus gave rise of a more lasting and enhanced adsorption of MB dye than pure MPCs.Further measurements were carried out to show the influence of reaction factors on the MB adsorption performance of ZnO/MPC composite, in which the dye adsorption capacity of ZnO/MPC composite increased apparently with the decreasing of particle size, while the adsorption rate of MB dye increased with the increasing of initial dye concentration, until a constant rate was obtained at 50mg-L-.This study provides a template-transfoming method for the synthesis of ZnO/MC composite by making use of Zn(OH)2 particles as the template to obtain mesopores. In cooperation of MPC's fast adsorption performance and ZnO's photocatalytic effect, the adsorption properties of ZnO/MPC composite, especially continuous adsorption performance was improved due to the in-situ re-activation of MPC. The experimental results indicates that the composite material have great potential and foreseeable applications in the fields of wastewater treatment, purification of potable water, adsorption/separation of macromolecules, etc. |
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