Synthesis, Structure Control And Application Of Nanoscaled Zero-valent Iron Spported By Ordered Mesoporous Silica

Due to large specific surface area and more active sites, the use of zero valent iron(Fe0) nanoparticles has been extensively investigated as reactive media for in situ environment remediation. However, the synthesis conditions are difficult to control and these Fe0 nanoparticles are tend to agglomerate and easily oxidized by air when exposed to air. All of these factors put forward a serious challenge for the preparation and application of Fe0 nanoparticles.Fe0 nanoparticles in ordered mesoporous silica(OMS) matrix were prepared by sol-gel one step synthesis-carbothermal reduction method. We investigated the affect of carbonization temperature and time on the formation of Fe0 in ordered structure and their stability in air. The composites were characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM), nitrogen adsorption and vibrating sample magnetometry(VSM). The thermal treatment process of the composites was investgated by thermogravimetric analysis-mass spectrometer(TGA-MS) and the formation mechanism for Fe0 nanoparticles in OMS matrix was proposed. Different factors on the effect of TNT treatment reaction rate and efficiency by using the obtained materials were studied. Moreover, the reaction kinetics and mechanism were researched. The results showed that:1. The optimized conditions for synthesis of the composite materials were at 800℃for 3 hours under a N2 atmosphere, heating rate of 1℃/min.2. The characterization results of synthetic materials showed that the iron particles in OMS matrix were dispersed in the form of nanoscaled zero-valent iron(NZVI). With increasing the percentage of iron species in OMS matrix, iron particles increased, BET surface area, total pore volume and average pore diameter had a decreasing trend.3. The results of the removal of TNT from solution showed that the removal rate of TNT is improved by an increase in Fe/Si molar ratio, dosage and temperature. The acidic and alkaline conditions are conducive to the improvement of reaction rate.4. Kinetic analysis showed that the pseudo-first order reaction law fit well of the reduction process of TNT. TNT is reduced to the corresponding amino compounds.