| With the acceleration of global industrialization and the improvement of people's living standard,the output of phosphorus wastewater is increasing year by year.A lot of these phosphorus wastewater emissions will cause eutrophication of water body,and then produces serious environmental consequences.Therefore,the research and development of high efficiency and low consumption dephosphorization technology will be of great practical significance.Electro-adsorption technology due to its high efficiency of phosphorus removal,electrode reproducibility and no secondary pollution and other characteristics is very suitable for application in the field of wastewater phosphorus removal.However,because the traditional electrode material activated carbon fiber's surface showed chemical inertness,phosphorus does not have the efficient selection of adsorption,and therefore must be modified to meet the treatment needs of phosphorus-containing wastewater.Taking into account the extremely large specific surface area and surface activity of activated alumina,this study will use active carbon fiber as the carrier,using sol-gel method to load a layer of activated alumina as a modified material on the surface of carbon fiber to prepare a highly efficient Phosphorus adsorption electrode material.And through the static adsorption experiment and XPS,FTIR,XRD spectrum characterization methods to optimize the electrode preparation and adsorption conditions.Furthermore,the phosphorus adsorption mechanism of the modified electrode was further studied.Finally,the recovery potential of the prepared material was evaluated by the regeneration experiment.The main conclusions of this study are as follows:(1)Aluminum load effects on phosphorus adsorption experimental results show that the main active material for phosphorus adsorption of carbon fiber aluminum electrode(ACF-Al)is activated alumina,and the carbon fiber only plays the role of conductor and carrier in this process.Scanning electron microscopy(SEM)results show that the huge surface area of carbon fiber is favorable for the high dispersion of activated alumina,and its developed pores can make the phosphorus solution flow smoothly inside the electrode.The results of XPS and FT-IR analysis showed that the surface hydroxyl groups produced by the combination of activated alumina and water were the main phosphorus adsorption active sites.(2)The effects of alumina loading and heat treatment temperature on the adsorption performance of the electrode were investigated.It was found that the optimum heat treatment temperature and aluminum loading were 375? and 0.3g respectively.Heat treatment is an important step in electrode preparation,which can promote the decomposition of organic groups in alumina precursors and the smooth formation of alumina.However,the study found that too high heat treatment temperature may lead to the collapse of activated carbon fiber pores,while promoting the active alumina crystal morphology changes and reduce its specific surface area.In the present study,alumina loading is the main active substance.When the load is low,the phosphorus adsorbability of the electrode will increase rapidly with the increase of the alumina loading.But after the load is more than 0.3g,the increase in alumina will cause the clogging of the pores of the activated carbon fibers and a serious overlap with the load.(3)The adsorption of phosphorus on ACF-Al electrode shows that the adsorption mechanism of P is mainly chemical adsorption,and physical adsorption also plays an important role in the adsorption process of phosphorus.On the one hand,activated alumina reacts with water to form a large amount of surface hydroxyl groups which can act as a Liweis acid to remove protons and bind to phosphate or exchange with phosphate in the form of ion exchange;On the other hand,after the ACF-Al electrode is energized,an electric double layer will be formed on its surface and physically adsorbed to the phosphate ions,and the chemical phosphorus adsorption capacity of the alumina can be enhanced.(4)The results of isothermal adsorption experiments and kinetics show that the applied voltage can significantly increase the adsorption effect of phosphorus on the electrode.This effect is especially prominent when the concentration of phosphorus is less than 200mg/L(twice the amount of adsorption).And when the phosphorus concentration is greater than 450mg/L the effect of this upgrade disappeared.XPS and FT-IR characterization showed that the ion exchange between phosphate and hydroxide was the main form of phosphorus adsorption,while the thermodynamic test showed that the applied voltage could significantly reduce the apparent activation energy of phosphorus adsorption and increase the adsorption of phosphorus heat.The effect of pH on Adsorption experimental results show that the ionization radius also plays an important role in the adsorption of phosphorus on the electrode,and dihydrogen phosphate has the highest adsorption capacity because of its minimum hydration radius.(5)The regeneration of ACF-Al electrode showed that the sodium carbonate solution was an ideal phosphorus desorption agent because of its moderate pH value and certain buffer property.The adsorption capacity of the electrode was 40% times lower than its initial adsorption capacity after the regeneration cycle of 14 times,indicating that the electrode has good regeneration performance. |
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