Decolorization Of The Wastewater Containing Non-biodegradable Dye By Heterogeneous Fenton Process Using Titanium Doped-Iron Oxide

In this work, a series of Ti doped-maghemite (Fe3-xTix)1-δO4 was synthssized by precipitation-oxidation and (Fe3-xTix)1-δO4/H2 was synthssized by H2 reduce (Fe3-xTix)1-δO4.The synthetic samples were characterized using the X-ray diffraction (XRD), N2 adsorption-desorption, Fourier infrared spectrum (FTIR), thermogravimetric and differential scanning calorimetry (TG-DSC), zero electric point (pHpzc), scanning electron microscopy (SEM), transmission electron microscope (TEM) and so on.The results show that (Fe3-xTix)1-δO4 and (Fe3-xTix)1-δO4/H2 were cubic spinel structure and Ti was introduced into the structure.The synthetic samples were typical mesoporous structure. Moreover, with the increase of Ti doped amount, the specific surface area and surface hydroxyl amount of the samples were increased.The introduction of Ti into the maghemite structure may stable the spinel structure.Firstly, the influence of Ti content in (Fe3-xTix)1-δO4 and the mechanism of methylene blue(MB) by heterogeneous Fenton reaction were conducted. UV-vis and FTIR analysis were used to studied the decolorization mechanism. Meanwhile, TOC analysis was used to investigate the mineralization of MB, and HPLC-MS was used to determine the degradation products. The results show that with the increment of Ti doped amount, the adsorption and degradation of MB on (Fe3-xTix)1-δO4 are improved. During the decolourization, MB was degraded into small molecular organics instead mineralization completely by heterogeneous Fenton of (Fe3-xTix)1-δO4 and there was no phase change happened in (Fe3-xTix)1-δO4 under the neutral pH.In the study of decolorization mechanism, the difference of structural Fe3+ and Fe2+ for hydroxyl radical generation of methylene blue during the heterogeneous Fenton reaction was also conducted by comparing (Fe3-xTix)1-δO4 and (Fe3-xTix)1-δO4 /H2.The Iron valence of (Fe3-xTix)1-δO4 and (Fe3-xTix)1-δO4 were Fe3+and Fe2+, respectively.Through the comparison of degradation rate constants, which was normalized by the adsorption capacity and specific surface area (kapp/qSBEr), (Fe3-xTix)1-δO4 exhibited comparative catalytic activity than (Fe3-xTix)1-δO4 /H2. The kapp/qSBET for (Fe3-xTix)1-δO4 and (Fe3-xTix)1-δO4 were 2.8×10-8 and 2.2×10-8, respectively.This indicates that the activity of structural Fe3+ in spinel is equal to structural Fe2+ for·OH generation during the heterogeneous Fenton decolorization of MB.Later, the important factors affecting the decolorization of MB during the heterogeneous Fenton by (Fe3-xTix)1-δO4 were discussed.The results show that with the increases of catalyst load, H2O2 concentration, pH and reaction temperature, the decoloraization rate of MB was promoted. However, the decolorization rate of MB was decreased with the increase of MB initial concentration. In addition, (Fe2Ti)1-δO4 has a good stability, and the decoloration rate of MB was still higher than 79% after five times repeated use.Finally, the decolorization and affect factors of anionic dye Acid Orange Ⅱ (AOⅡ) by heterogeneous Fenton using the (Fe2Ti)1-δO4/H2 were studied.The results show that the degradation of AO Ⅱ by heterogeneous Fenton using the (Fe2Ti)1-δO4/H2 follow the Eley-Rideal model and the degradation process conforms to the pseudo-first order kinetics.The nitrogen and nitrogen double bond and naphthalene rings of the AO Ⅱ fracture were opened. Increase the catalyst load, hydrogen peroxide concentration and lower reaction pH can accelerate the degradation of AO Ⅱ. With the increase of repeated use, the decomposition rate of AO Ⅱ decline, maybe of Fe2+ of the catalyst surface was oxidated on the oxidation environment.