Application Of Iron-based Amorphous Alloys In Phenol Wastewater Treatment

The phenolic wastewaters are characterized by intricacy of component, high of concentration, deficit of biochemistry, so directly discharge of them will cause serious pollution to the environment. Therefore, researchers focus on the investigation of searching an efficient and environmental friendly method phenolic compounds treatment. Phenol was used as the object of this searching since it is a raw material for the synthesis of complex phenolic compounds, an intermediate product in the oxidation pathway of higher molecular weight aromatic hydrocarbons and it is the most prominent phenolic compounds in wastewater. The classical Fenton reaction is the most attractive method of Advanced Oxidation Processes (AOPs). Compared with other technologies Fenton reaction has many advantages, such as simplicity of operation, efficiency of reaction and environmental friendly. In this research, iron-based amorphous alloys have been used as catalyst in heterogeneous Fenton reaction.Through the analysis of High Performance Liquid Chromatography (HPLC), we compared the phenol removal efficiency using Fe78Si9B13amorphous alloy, Fe2+and zero-valent iron (ZVI) as catalyst respectively. The Fe78Si9B13amorphous alloy showed higher catalytic activity than the Fe2+and ZVI. In the same reaction conditions, phenol can be completely degrade into CO2and H2O under the action of Fe78Si9B13amorphous alloy. Only a small proportion of phenol was completely mineralized with Fe2+and ZVI as catalyst, and most of it was transformed into some toxic intermediates.In order to find the optimum reaction conditions for the degradation of1000mg/L of phenol aqueous solution, the influences of main operating parameters such as reaction temperature, catalyst amount, hydrogen peroxide dosage and initial pH of solution on phenol degradation rate were investigated. The maximum mineralization of phenol was achieved at60℃,6g/L Fe78Si9B13,0.31mol/L hydrogen peroxide, with an initial pH of2.5. More than99%of phenol was completely removed under the optimum conditions within10min. When the initial concentration of phenol solutions ranging from50mg/L to2000mg/L, the same excellent removal efficiency was obtained under the optimum conditions. The Fe78Si9B13amorphous alloy exhibited high stability in recycling experiments and showed excellent reuse performance even after continuous operations of8cycles.Based on the results of the experiment, the degradation process of phenol was showed as follows:the hydrogen peroxide was adsorbed onto the surface of Fe78Si9B13amorphous alloy and generated hydroxyl radicals. The hydroxyl radicals first react with phenol in the ortho and para positions to form catechol and hydroquinone, respectively. Further oxidation of the dihy-droxylbenzenes then occurs to produce benzoquinones and then the ring opens to form lower molecular weight organic compounds which are ultimately oxidized to CO2and H2O. Kinetics analysis based on the experimental dates elucidated that the phenol degradation process can be described by the first-order kinetic model.Structural analysis was investigated by XRD, DSC and SEM and the results demonstrated that there is a closed relationship between the catalytic activities and composition of the Iron-based amorphous alloys. The addition of Nb and Cu increased the alloys thermal stability and enhanced the bond energy between alloy surface and the passivation layer, which lead to the decrease of their catalytic activity. After treated at100℃for24h, the catalytic activity of the two amorphous alloys all increased.