Synthesis Of NZVI/SBA-15 Composite And Mechanism Research On Removal Of Nitrobenzene In Aqueous Solution

Due to its tiny size, its large surface area and high surface reactivity, NZVI has been considered as a promising environmental remediation technology. However, NZVI is prone to agglomerate and easily oxidized by oxygen when exposed to air, leading to restrict its application. Therefore, the study on the enhancement of the stability of NZVI and its high surface reactivity has become the hot topics in related researches.In this present study, we chose SBA-15 as a support material to produce stable NZVI dispersions. Moreover, due to its high adsorption capacity SBA-15 can increase the degradation efficiency of pollutants dramatically. The NZVI/SBA-15 composite was synthesized by incipient wetness impregnation, calcinations and reduction, which exhibited the synergetic effect of high adsorption capacity of SBA-15 and high reducibility of NZVI. The NZVI/SBA-15 composite was characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM), and N2 adsorption/desorption. Furthermore, the adsorption and degradation process of nitrobenzene on NZVI/SBA-15 composite was investigated, and the effect factors of nitrobenzene removal were discussed. The pathway of NZVI reducing nitrobenzene and the reduction mechanism of nitrobenzene was also researched. The results showed that:(1) with increasing the percentage of iron species in NZVI/SBA-15 composite, the orderity,the BET surface area and the total pore volume decreased, but still maintained the structure of SBA-15.α-Fe0 nanoparticles were well dispersed in the channels of SBA-15. However, agglomeration of iron particals unsupported took place, leading to increase its partical size.(2) The removal rate of nitrobenzene from aqueous solution on SBA-15, NZVI and NZVI/SBA-15 composite was 51.59%.56.01% and 94.94% respectively after 12h of reaction. The nitrobenzene removal rate by the NZVI/SBA-15 composite was enhanced apparently owing to the synergetic effect of high adsorption capacity of SBA-15 and high reducibility of NZVI.(3) The removal rate of nitrobenzene increased as the percentage of iron species in NZVI/SBA-15 composite and dosage increased. The acidic condition was conducive to enhancement of reaction rate, but the alkaline condition prevented the reaction rate. The removal rate of nitrobenzene decreased as the initial concentration of nitrobenzene increased.(4) The pathway of nitrobenzene reduction by NZVI was described as:nitrobenzeneâ†'nitrosobenzeneâ†'phenylhyoxylamineâ†'aniline. It was the Fe2+ associated with the iron in the NZVI/SBA-15 composite that was mainly responsible for nitrobenzene reduction.