Synthesis And Application Of Ordered Mesoporous Carbon Supported With Nanoscale Zero-valent Iron

As nanoscale zero-valent iron (NZVI) possesses small size and significant reduction reactivity, NZVI may aggregate easily and be oxidized facilely, which limit its application. For these considerations, we proposed to design composite materials consisted of NZVI supported with ordered mesoporous carbon (OMC). OMC have the advantages in ordered meso-structrue, large surface area and big pore volume. OMC acted as supports for NZVI may controll the aggregation and oxidation of NZVI and optimize their reactivity and stability. In this work, NZVI supported on OMC composite materials (NZVI/OMC) was synthesized. The synthesis route of NZVI/OMC composite is introduced, including the synthesis of OMC using phenol-formaldehyde resol (PF) polymerized in basic medium as carbon precursor and triblock copolymer F127 as template agent, incipient wetness impregnation of iron ion from ferrous sulfate, liquid phase reduction following previous calcination. NZVI/OMC composite possesses ordered mesoporous structure and the supported NZVI dispersed well with small size. The composite exhibits synergistic effects of adsorption and reduction. The magnetically separable mesostructured Fe-containing carbon composite materials (Fe/OMC) with highly ordered structure were synthesized via soft-templating routes, using PF as carbon precursor, F127 as template agent, inorganic iron salts ferric nitrate as metal precursor in one pot. The organic-inorganic-triblock copolymer co-assembly route was induced by solvent evaporation. Both the NZVI/OMC and Fe/OMC composite materials were characterized by X-ray diffraction, N2 adsorption/desorption and transmission electron microscopy. Nitrobenzene(NB) has been chosed as the objective pollutant to evaluate the synergistic effects of adsorption and reduction ability of NZVI/OMC. And the adsorption behaviours of Fe/OMC for 4-chlorophenol(4-CP) has been evaluated. The adsorption capacity and magnetic property of Fe/OMC have been investigated. Following conclusions can be concluded。1. The NZVI/OMC composite maintained ordered mesoporous structure. Iron species existed inα-Fe0 states and NZVI dispersed well on the matrix of OMC served as supports. The iron nanometal particles were maintained in certain size(10-50nm). NZVI/OMC composite exhibited more efficient removal effect for NB than both pure OMC and non-supported NZVI. The removal action of NZVI/OMC for NB was a combined synergistic effects of high adsorption capacity and significant reduction reactivity. NB was reduced by NZVI efficiently and the final reductive product was anline. The removal efficiency of NB by NZVI/OMC increased as the dosage of NZVI/OMC increased. Acidic conditions was beneficial for the removal process. The adsorption and reduction effect would be hastened as the concentration of NB increased.2. The Fe/OMC composite possessed ordered two-dimension hexagonal mesoporous structure as the ratio of n(Fe)/n(R) was 0.05-0.15. The ordering decreased following the increase of the ratio. As the ratio was 0.20, the composite lost the ordering. Ferric species were finally reduced toα-Fe0 during the carbothermal treatment process at 700℃. The nanometal particales with a diameter of 10～20nm dispersed highly in the carbon matrix. Fe/OMC composite possessed large surface area and bigger pore size than OMC. The adsorption capacity of Fe/OMC for 4-CP was 267mg/g as the reaction temperature was at 20℃. The composite exhibited magnetic property and were magnetically separable. The removal efficiency of 4-CP by Fe/OMC increased as the dosage of Fe/OMC increased. Acidic condition was beneficial for the adsorption process. The removal efficiency decreased significantly as the reaction temperature was at 30℃.