Preparation Of Sulfonic Acid Functional Group Modified Mesoporous Silica Supporing With Iron Oxide And Its Photo- Fenton Catalytic Oxidation Behavior

In recent years, persistence organic pollutants have become one of the most important environmental problems in the world. Nowadays, as an important advance oxidation processes (AOPs), heterogeneous Fenton process is being widely used for the degradation of organic contaminants. To develop a heterogeneous Fenton catalyst which is possessed of few reagent consumption, good degradation effect, wide application rage, little iron leaching, stable catalytic activity in repetitive reaction cycle is an important trend in the Fenton catalysis. In our study, a composite nanoparticle, the mesoporous silica containing sulfonic acid functional groups (SO3HNH-SiO2) was successfully decorated with ferric oxide nanoclusters. Various techniques, such as SEM, TEM, BET, FT-IR, XRD and XPS, were applied to character structure and properties of the catalyst. The non-biodegradable azo dye, Reactive red (X-3B), was chosen as a target contaminant to investigate the catalytic property of the catalyst in visible light Fenton system. The effects of reaction conditions on its performance of X-3B degradation were exploited in detail. Meanwhile, the stability of catalyst was evaluated by recycle experiments and iron leaching.The result shows that mesoporous silica nanopartic les (NH2-SiO2) exhibited the uniform size and good dispersion. The surface of the NH2-Si02 was functionalized by sulfonic groups, while its hydrophilic improved. The in situ growth of a-Fe2O3 nanoclusters on SO3HNH-SiO2 were achieved by hydrothermal treatment and calcination progress. The a-Fe2O3 nanoclusters were linked with SO3HNH-SiO2 by Fe-O bond and uniformly dispersed on the support. In the photo-Fenton system, X-3B solution was complete degraded by Fe/SO3HNH-SiO2 under the optimum preparation condition. Under visible light radiation, more electron-hole could be generated by a-Fe2O3, which promoted electron transfer between FeⅡ and FeⅢ. And visible light could also activate dye molecules. Meanwhile, the synergetic effect of sulfonic acid functional group and α-Fe2O3 nanoclusters facilitated the decomposition of H2O2. Sulfonic acid group bonded iron ion surely had more extended space, which resulted in more orbital-overlapping between the iron ion and surface peroxide species. Thus, the electron transfer between them was enhanced. The catalytic activity of Fe/SO3HNH-SiO2 in the photo-Fenton reaction can be influenced by pH of dye solution, H2O2 concentration and catalyst dosage. The degradation efficiency of X-3B in 120 min was 99.0% while the TOC removal rate was 64.4% for the first oxidation when the initial conditions were [X-3B]= 100 mg L-1, [Cat.]= 0.5 g L-1, pH=6.0, [H2O2]= 5.0 mmol L-1 under room temperature. The X-3B degradation performance on the reused catalyst showed a slight difference with the first oxidation cycle. The degradation efficiency of X-3B was above 91% and TOC removal rate was 51.7% for the third oxidation cycle. The iron leaching remained below 0.24 mg L-1, which indicated that the prepared catalyst presents high stability and vast industrial application potential.