铁锰材料活化过硫酸盐去除水中难降解有机污染物的机制与效能

发布时间：2018-06-22 18:59

本文选题：高级氧化技术 + 过硫酸盐　；参考：《吉林大学》2017年博士论文

【摘要】：基于硫酸根自由基(SO4-·)的高级氧化技术是近年来发展起来的处理难降解有机污染物的新技术,具有氧化能力强,氧化剂稳定性好,受pH影响小等优点,具有广阔的应用前景。应用过硫酸盐高级氧化技术的关键是高效、快速地活化过硫酸盐产生SO4-·。在诸多活化方法中过渡金属均相活化耗能少,技术难度低,具有明显的优势。但过渡金属离子的引入易引起环境的二次污染,因此制备廉价易得且无二次污染的非均相活化材料成为趋势。铁、锰元素在地壳中赋存量大,原材料廉价易得,二次污染风险小,因此开发基于铁锰的非均相活化材料用于去除水体中难降解有机污染物具有重要意义。据此,本研究开发了系列铁锰基活化材料,构建了其活化过硫酸盐去除苯胺类及氯酚类难降解有机污染物的高级氧化技术,系统研究了各方法的作用机制和效能。主要内容包括:(1)通过系列实验优化了 Fe~(2+)活化过硫酸盐氧化去除苯胺的条件,并探究了这一条件下水中常见阴阳离子对苯胺去除的影响,在本实验条件下Fe~(2+)活化过硫酸盐体系可以有效去除苯胺,反应60min内苯胺的去除率可达86.33%,反应的最佳条件为3.3mmol/LFe~(2+)和4.4mmol/L过硫酸盐,即苯胺/过硫酸盐/Fe~(2+)的摩尔比为10/4/3。在Fe~(2+)活化过硫酸盐去除苯胺的最优条件下,水中常见阴离子的存在如CO32-、PO43-、SO42-、HCO3-和NO3-对苯胺的降解有抑制作用。按照抑制作用由强到弱排序为PO43-CO32-SO42-HCO3-NO3-。水中常见的阳离子(Na+、K+、Mg~(2+)和Ca~(2+))对Fe~(2+)活化过硫酸盐去除苯胺的抑制作用可以忽略。相比于各离子单独存在的情况,实际水体中存在的各阴离子对Fe~(2+)活化PS去除苯胺的抑制作用具有叠加效果。在将该技术应用于实际时,需要充分考虑共存离子的影响。(2)采用超声共沉淀法制备了 Fe_3O_4磁性纳米颗粒,通过XRD和TEM表征,该磁性纳米颗粒为直径10-30nm的准球面结构。该Fe_3O_4磁性纳米颗粒可有效活化PS去除水中的对硝基苯胺。在PS投加量为8mmol/L,Fe_3O_4MNPs投加量为5.32g/L,pH=7.0±0.2,反应温度为25℃时,反应300min后PNA降解率能达到1000%,TOC去除率达67%。根据Fe_3O_4MNPs活化PS降解PNA机理,推导出PNA降解的准一级反应动力学方程。实验结果验证了在不同影响因素条件下,PNA的降解均遵循准一级反应动力学,得出了 PNA降解的表观速率常数,在前述条件下,PNA降解的表观速率常数为0.00176min-1。Fe_3O_4MNPs虽可有效活化PS降解PNA,但在重复利用四次后,失去活化性能,该材料的不稳定性限制了其在污水处理中的应用。(3)通过气固反应法制备了 Fe~0@Fe_3O_4铁合金。研究结果表明Fe~0@Fe_3O_4铁合金可有效活化PS去除水中PNA,相比投加同样质量Fe_3O_4活化过硫酸盐去除PNA的效率提高了 90%以上。构建了铁合金活化PS降解PNA的高级氧化系统,在PS投加量为30mmol/L,Fe~0@Fe_3O_4铁合金投加量为0.05g/L,反应温度为25℃时,反应180min后PNA降解率可达1000,且PNA的降解规律符合准一级动力学方程。在上述条件下,PNA降解的表观速率常数为0.02898min-1。通过自由基的淬灭和电子自旋共振(EPR)分析,鉴别了活性自由基的种类为羟基自由基和硫酸根自由基。研究还阐明了 Fe~0/Fe_3O_4核壳结构合金纳米材料活化PS降解PNA的反应机制。将Fe~0/Fe_3O_4核壳结构合金纳米材料作为PS活化剂引入高级氧化体系中,实现了 Fe_3O_4表面Fe(Ⅱ)的快速再生,大幅提高了 Fe_3O_4的活化效能。(4)采用水热合成法制备了 α-MnO_2纳米线状材料,并构建了其活化PS降解2,4-DCP的高级氧化体系。研究发现,该体系去除污染物性能优异,30℃,20mmol/LPS,0.2g/Lα-MnO_2 的初始条件下,180min 内 100mg/L2,4-DCP 的降解效率高达90.2%,TOC去除率达62.37%。根据其主反应机理,推导出其反应动力学方程为,在前述条件下,2,4-DCP降解的半衰期为18.1min。自由基淬灭实验和EPR结果表明体系中主要活性自由基为硫酸根自由基和羟基自由基,且自由基的量随时间延长而增加。该材料稳定性好,重复利用五次后仍可有效活化PS氧化降解2,4-DCP,去除率仍可高达81.2%,在实际应用中可降低污水的处理成本。(5)为在工程中能够实现α-MnO_2纳米线的回收和重复利用,本研究改进了传统水热合成方法,首次制备出Fe_3O_4/α-MnO_2线状纳米复合材料。研究发现,该材料可高效活化PS去除水中的2,4-DCP,在Fe_3O_4/α-MnO_2复合材料投加量为0.4g/L,PS浓度为30mmol/L,反应温度为30℃时,2,4-DCP的去除率180min内达到96.3%,半衰期为26.1min。明确了 Fe_3O_4/α-MnO_2复合材料活化PS体系中2,4-DCP的降解反应动力学规律,及Fe_3O_4/α-MnO_2复合材料活化PS降解2,4-DCP的反应机制。四次回收并重复使用后,Fe_3O_4/α-MnO_2复合材料仍具有良好的活化性能,2,4-DCP的降解率仍高达94.5%。该材料活化效能高,且稳定性好,易于重复利用,可广泛应用于污水处理。
[Abstract]:The advanced oxidation technology based on radical sulfate radical (SO4-) is a new technology for the treatment of refractory organic pollutants in recent years. It has the advantages of strong oxidation capacity, good oxidizing agent stability and small effect on pH. It has a broad application prospect. The key to the application of sulphate advanced oxidation technology is to efficiently and quickly activate persulfate. Salt produced SO4-. In many activation methods, the transition metal has less energy consumption, low technical difficulty and obvious advantages. However, the introduction of transition metal ions is easy to cause two pollution of the environment. Therefore, the preparation of inexpensive and non two pollution heterogeneous activated materials becomes the trend. Iron and manganese elements are large in the crust and raw materials Therefore, the development of a series of ferromanganese based activation materials and the construction of the advanced oxidation techniques for the removal of aniline and chlorophenols to remove the refractory organic pollutants by activated persulfate have been developed in this study. The mechanism and effectiveness of various methods are systematically studied. The main contents are as follows: (1) the conditions for the removal of aniline by Fe~ (2+) activated persulfate oxidation were optimized through a series of experiments, and the effects of the common Yin and yang ions on the removal of aniline in the water were investigated. Under this experimental condition, the Fe~ (2+) activated persulfate system could be effectively removed. In addition to aniline, the removal rate of aniline in 60min can reach 86.33%. The optimum conditions for the reaction are 3.3mmol/LFe~ (2+) and 4.4mmol/L persulfate, that is, the molar ratio of aniline / persulfate /Fe~ (2+) is the optimal condition for 10/4/3. in the removal of aniline by Fe~ (2+) activated persulfate, the presence of common anions in water, such as CO32-, PO43-, SO42-, SO42-, and pairs. The degradation of aniline has an inhibitory effect. The inhibition effect of the common cations in PO43-CO32-SO42-HCO3-NO3-. water (Na+, K+, Mg~ (2+) and Ca~ (2+)) from strong to weak (K+, Mg~ (2+) and Ca~ (2+)) can be neglected in the inhibition of Fe~ (2+) activated persulfate removal of aniline. Compared with the existence of individual ions alone, the anions in the actual water body are to Fe~ (2+). The inhibitory effect of activated PS on Aniline Removal has superimposed effect. When applying this technique to practice, the effect of coexistent ions should be fully considered. (2) Fe_3O_4 magnetic nanoparticles are prepared by ultrasonic co precipitation method. The magnetic nanoparticles are characterized by XRD and TEM. The magnetic nanoparticles are quasi spherical structures of 10-30nm diameter. The Fe_3O_4 magnetic nanoparticles PS can effectively activate PS to remove p-nitroaniline in water. When the dosage of PS is 8mmol/L, the dosage of Fe_3O_4MNPs is 5.32g/L, pH=7.0 + 0.2, and the reaction temperature is 25, the degradation rate of PNA can reach 1000%, and TOC removal rate reaches 67%. according to Fe_3O_4MNPs activation PS degradation mechanism. The results show that under the conditions of different influence factors, the degradation of PNA all follows the quasi first order reaction kinetics, and the apparent rate constant of PNA degradation is obtained. Under the foregoing conditions, the apparent rate constant of PNA degradation is 0.00176min-1.Fe_3O_4MNPs can effectively activate PS to degrade PNA, but after repeated use of four times, the activation property is lost, this material is lost. The instability limits its application in sewage treatment. (3) Fe~0@Fe_3O_4 ferroalloys have been prepared by gas solid reaction. The results show that Fe~0@Fe_3O_4 ferroalloys can effectively activate PS to remove PNA in water and increase the efficiency of PNA by adding the same mass Fe_3O_4 activated persulfate to PNA. The activation PS drop of the ferroalloy is constructed. To solve the advanced oxidation system of PNA, when the dosage of PS is 30mmol/L, the dosage of Fe~0@Fe_3O_4 ferroalloy is 0.05g/L, the reaction temperature is 25 C, the degradation rate of PNA can reach 1000, and the degradation law of PNA conforms to the quasi first order kinetic equation. Under the above conditions, the apparent rate constant of PNA degradation is quenched by the free radical of 0.02898min-1.. With the electron spin resonance (EPR) analysis, the species of active radicals are identified as hydroxyl radical and radical radical. The reaction mechanism of Fe~0/Fe_3O_4 nuclear shell structure alloy nanomaterials to activate PS to degrade PNA is also elucidated. The Fe~0/Fe_3O_4 nuclear shell alloy nanomaterials are introduced into the advanced oxidation system as PS activators. The rapid regeneration of Fe (II) on the surface of Fe_3O_4 has greatly improved the activation efficiency of Fe_3O_4. (4) the nano linear material of alpha -MnO_2 was prepared by hydrothermal synthesis, and the advanced oxidation system for the activation of PS to degrade 2,4-DCP was constructed. The study found that the system was excellent in removal of pollutants, with the initial conditions of 30, 20mmol/LPS, 0.2g/L a -MnO_2, 180. The degradation efficiency of 100mg/L2,4-DCP in Min is as high as 90.2%, and the removal rate of TOC reaches 62.37%.. The reaction kinetics equation is deduced according to its main reaction mechanism. Under the foregoing conditions, the half-life of 2,4-DCP degradation is 18.1min. radical quenching experiment and EPR results show that the main active radicals in the system are radical radical and hydroxyl radical of sulfate radical, The amount of free radical increases with time. The material has good stability and can effectively activate PS oxidation and degradation of 2,4-DCP after repeated use of five times. The removal rate can still be as high as 81.2%. In practical application, the cost of wastewater treatment can be reduced. (5) the recovery and reuse of alpha -MnO_2 nanowires can be achieved in engineering. This study improved the tradition. Fe_3O_4/ alpha -MnO_2 linear nanocomposites were prepared for the first time by hydrothermal synthesis. It was found that the material can efficiently activate PS to remove 2,4-DCP in water. When the dosage of Fe_3O_4/ alpha -MnO_2 composite is 0.4g/L, PS concentration is 30mmol/L, and the reaction temperature is 30, the removal rate of 2,4-DCP is up to 96.3%, and the half-life is clear. The kinetics of the degradation reaction of 2,4-DCP in the activated PS system of Fe_3O_4/ alpha -MnO_2 composite and the reaction mechanism of Fe_3O_4/ alpha -MnO_2 composite activated by PS to degrade 2,4-DCP. After four recovery and repeated use, the Fe_3O_4/ alpha -MnO_2 composite still has good activation properties, and the 2,4-DCP degradation rate is still up to the activation efficiency of the 94.5%. material. It can be widely used in sewage treatment because of its high efficiency, good stability and easy reuse.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X703

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