【作者】 张伟；

【导师】 周健； 方俊华；

【作者基本信息】 重庆大学 ， 市政工程， 2017， 硕士

【摘要】 随着全球工业化的加速及人民生活水平的不断提高,含磷废水的产量正逐年上升。这些含磷废水的大量排放将造成水体的富营养化,进而产生严重的环境恶果。因此高效低耗的污水脱磷技术的开发研究将具有极其重要的现实意义。电吸附技术由于其除磷的高效性、电极的可再生性以及无二次污染等特点而十分适宜于在污水除磷领域的运用。但电吸附技术传统的电极材料活性炭纤维由于其表面呈现化学惰性,对磷不具备高效的选择吸附性,因而必须对其进行改性以适应含磷废水的处理需求。考虑到活性氧化铝极大的比表面积与表面活性,研究将以活性炭纤维为载体,采用溶胶凝胶法在其表面负载一层活性氧化铝作为改性物质,制备出一种可高效吸附除磷的电极材料。并通过静态吸附实验及XPS、FT-IR、XRD谱等表征手段考察电极的优化制备及吸附条件,并在此基础上进一步研究改性电极的磷吸附机理,最后通过再生实验对制备材料的回收潜力进行评估。本研究的主要结论如下:(1)铝负载量对磷吸附的影响实验结果表明,载铝活性炭纤维电极(ACF-Al)的主要磷吸附活性物质为活性氧化铝,炭纤维在此进程中主要起导体和载体的作用。扫描电镜(SEM)表征结果显示碳纤维巨大的表面积有利于活性氧化铝的高度分散,而其发达的孔隙能够使磷溶液在电极内部顺畅通行。而XPS与FT-IR分析结果显示活性氧化铝与水结合后产生的表面羟基是电极主要的磷吸附活性位点。(2)考察了氧化铝负载量与热处理温度对电极磷吸附性能及机理的影响,发现最佳的热处理温度与铝负载量分别为375℃与0.3g。热处理是电极制备的一个重要步骤,它能够促使氧化铝前驱体中的有机基团的分解与氧化铝的顺利生成。而研究发现过高的热处理温度可能导致活性炭纤维孔隙的坍塌,同时将促使活性氧化铝结晶形态的改变而降低其比表面积。氧化铝负载物在本研究中是作为电极吸附磷的主要活性物质,在负载量较低时,电极的磷吸附性能将随氧化铝负载量的增加而快速提升,但在负载量超过0.3g后,氧化铝的增加将导致活性炭纤维孔隙的堵塞与负载物严重的重叠分布。(3)ACF-Al电极对磷的吸附实验表明其对磷的吸附机理总体表现为化学吸附,同时物理吸附也在磷吸附的过程中起重要作用。一方面活性氧化铝与水结合后能够生成大量的表面羟基,这些表面羟基能够作为Liweis酸脱去质子后与磷酸根结合或与磷酸根以离子交换的形式实现对磷的吸附;另一方面,ACF-Al电极通电后将在其表面形成双电层并对磷酸根离子形成物理吸附,同时也可以强化氧化铝的化学磷吸附能力。(4)等温吸附实验与动力学实验研究表明,外加电压可以大幅提高电极对磷的吸附效果,这种提升效应在溶液磷浓度低于200mg/L时尤为突出(吸附量为开路时的两倍),而当磷浓度大于450mg/L后这种提升的效果消失。XPS与FT-IR表征结果显示,磷酸根与氢氧根的离子交换作用是磷吸附的主要形式,而热力学试验结果则表明外加电压可以显著降低磷吸附的表观活化能同时增大磷的吸附热。pH对吸附的影响实验结果显示,离子水合半径对磷在电极上的吸附也起着至关重要的作用,磷酸二氢根由于水合半径最小使得其成为吸附活性最高的磷形态。(5)ACF-Al电极再生实验表明,碳酸钠溶液由于其具有适中的pH值和一定的缓冲性能使其成为理想的磷脱附药剂,电极在再生循环14次后其吸附容量才首次低于其初始吸附能力的40%,表明此种电极具有良好的再生性能。更多还原

【Abstract】 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.更多还原