| With the rapid development of modern agriculture and industry, water pollution is more and more serious, especially the organic pollution of water. The Fenton technology is widely used for its high efficiency, but the homogeneous Fenton achieve a good effect only under the acid reaction conditions, heterogeneous Fenton has been gradually valuedused in water treatment for its fast reaction rate, non-secondary pollution and widely reaction p H range.Layered double hydroxides(LDHs) are a kind of functional materials with a permanent positive charge and have hydrotalcite layered crystal structure. Due to theirs unique electrical properties, layered structure and the exchangeable characteristic of interlayer anions, LDHs are increasingly used in many fields, such as chemical industry, industrial catalysis, medicine and environmental sciences. In this research, the heterogeneous Fenton reaction of LDHs which contain iron(including Fe(â…¡)/Fe(â…¢)-LDH and Mg/Fe-LDH) is the main research background, methyl orange is the target object, different kind of LDHs with different interlayer anions and Fe element were carried out to degrade the methyl orange with the exist of H2O2, the effect of iron and interlayer anion in the Fenton reaction were discussed. The main research results and conclusions of this paper were as follows:(1) Layered Fe(II)-Fe(III) hydroxides(green rusts, GRs) intercalated with dodecylbenzenesulfonate anions were easily synthesized by the co-precipitation method at room temperature, namely organic green rust(DBS-GR). The DBS-GR were characterized by XRD, FT-IR, SEM, indicating that the DBS-GR was synthesized successfully by this simple and rapid method, and the DBS- was anti-parallel packing model. The high removal ratio of MO(96%) by DBS-GR was observed after 15 min in the presence of H2O2. In the process of Fenton reaction, hydroxyl radicals attacked the azo bond of methyl orange molecules, and made its fracture decomposition until to small molecule organic matters, and CO2 and H2 O. And the initial p H value of heterogeneous Fenton system could be extended to the neutral with the same result of the acid environment.(2) The oxidation products of DBS-GR(named as DBS-GR*) were used for the second Fenton reaction again, its result could reach more than 95% while the removal ratio of the oxidation products of SO4-GR(named as SO4-GR*) was only 27.7%. DBS-GR* could be used for four times Fenton reactions, and its removal ration was also more than 90% after the forth cycle experiment, and the layer structure still remained. So the DBS-GR* is a kind of very potential heterogeneous Fenton reaction materials.(3) Compare the stability of DBS-GR and SO4-GR, no matter the slow oxidation in the natural condition, quickly oxidation(with H2O2) or in the Fenton system, DBS-GR still maintained the layered structure of LDH. Fe2+ was oxidized to Fe3+ and turned to the oxidation products which structure was layer goethite with DBS- anions in the interlayer. While the original layer structure of inorganic green rust was damaged and oxidation product turned to goethite or magnetite.(4) Mg/Fe-LDHs which were synthesized with different metal proportion and aging time had different light-Fenton effect to methyl orange, with the improve of iron ion content, light-Fenton effect increased accordingly, the shorter of the aging time, the bigger of the specific surface area, iron ions more exposure to the outer layer, the adsorption and light-Fenton effect were increase accordingly. The light-Fenton result of the 1:1 Mg/Fe-LDH which aging time was 0h was best, decolor rate reached 80% after 3h. Mg/Fe-LDH light-Fenton mechanism is solid surface heterogeneous catalytic, under the irradiation of ultraviolet light, ferric iron ion on the surface of LDH was be reduced to bivalent iron ion, and then reacted with H2O2 produced hydroxyl radicals. |
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