Development Of Novel Iron-based Bimetallic Fenton-like Catalysts And Application In Dye Removal

Organic wastes originated from printing and dyeing industry, bring about huge environmental pollution and health risks to the people due to the high colority, great quantity, complicated constituents and non-biodegradable property. More importantly, water quality is still difficult to meet discharge standard after treatment by traditional methods. At the same time, heterogeneous Fenton-like catalytic technology, one of the advanced oxidation technologies (AOTs), was intensively concerned and investigated because of its eco-friendly nature, simple equipment and fast speed. However, disadvantages of the heterogeneous Fenton-like catalysts such as poor catalytic activity, narrow pH range and low efficiency of utilization of H2O2 hinder the industrial application. Therefore, it is essential to study and develop novel heterogeneous Fenton-like catalysts with low cost, high efficient, wide pH range and straightforward properties.In this paper, mesoporous SBA-15, has large surface area and ordered pore size, was chosen to as the support in order to improve the dispersion, enhance the catalytic activity and strengthen the recyclability. While iron was used as basic element of the catalysts, and Ni, Cu, Al and Pd were co-loaded by one of them or together. Under this condition, iron-based bis (poly) metal Fenton-like catalysts were successfully prepared and novel structures and electronic properties were obtained. Ascribed to the confinement effect of SBA-15 and synergistic effects of the mixed metals (oxides), Fe (III)/Fe(II) cycle and catalytic activities of the Fenton-like catalysts were greatly accelerated. The main contents of this work are shown as follow.(1) A highly active and magnetic nickel-iron Fenton-like catalyst was prepared by fabricating uniform and highly dispersed mixed oxides into the mesoporous material SBA-15. The catalyst achieved high removal rate (reached up to 97.6% in 30 min and almost 100% in 1 h) and about 60% TOC removal, which are much higher than the monometallic loaded catalysts under same conditions. What is more,65.81% of TOC removal was obtained by this catalyst and more than 95% H2O2 in the system participated in mineralization of dye when initial concentration of H2O2 is 4.0 mM, demonstrating amazing ability of mineralization and high utilization efficiency of H2O2. Last but not least, this catalyst showed good reusability and can be easily separated using a magnet. Characterization and mechanism analysis showed that high catalytic activity owes to uniform size and homogeneous distribution of the nanoparticles and superior synergistic effects between Fe and Ni species in the catalyst.(2) On the basis of that Pd can in-situ generated hydrogen peroxide, a novel FePd bimetallic Fenton-like catalyst was fabricated, which showed excellent catalytic activity in present of artificially added H2O2 and in-situ generated H2O2. Under the latter condition,98.6% removal of Acid Red 73 was obtained in 1 h, which is much higher than Pd loaded catalyst (29.5%), Fe loaded catalyst (less than 3%) and the catalyst loaded on SiO2 without channels or pores (51.6%). The presence of H2O2 was directly detected and confirmed by spectrophotometric determination. High activity originates from the combination of confinement effect of porous channels of SBA-15, synergistic effects between Fe species and Pd species, and coordination of adsorption and catalysis in Fenton-like reaction.(3) By taking advantage of the Lewis acid sites from Al, Lewis acid and Fenton catalytic properties from Cu, a kind of iron-based Fenton-like catalyst was prepared and can be used in neutral environment. Under the conditions of pH=7, the catalyst displayed high removal rate for the cationic dye Rhodamine B and anionic dye Acid Red 73. Investigation of preparation conditions showed that the content of Al, Fe and Cu molar ratio (optimum ratio is 1:3) have significant impacts on the catalytic activity, while reduction temperature has nothing to do with it. Characterization and mechanism showed that Al not only provides an acidic microenvironment for the reaction, but also improves the dispersion of active component on the support. Furthermore, Cu species can form a redox cycle to produce ·OH and facilitate the reduction of the Fe(Ⅲ) to Fe(Ⅱ) in Fenton-like reaction, thus the dye degradation in neutral pH was accelerated.