铁系层状双金属氢氧化物非均相类芬顿反应及其机理研究
发布时间：2018-08-13 20:49
【摘要】：随着现代工农业飞速发展,水体污染越来越严重,其中尤以水中有机物的污染最为严重。在水中有机污染物的处理方法中,芬顿技术以处理效率高、反应迅速快的特点被广泛应用,因为均相芬顿必须在酸性的反应条件下才能达到较好的处理效果,非均相芬顿法以其较宽的p H值范围逐渐被重视,在水处理方面得到了广泛的应用。层状双金属氢氧化物(Layered double hydroxides,简称LDHs)是一种带有永久正电荷的具有水滑石层状晶体结构的功能材料。由于其独特的性质,层状结构以及层间阴离子的可交换性,在材料、化工、工业催化、医药和环境科学等领域具有潜在的应用价值。本研究以含铁LDH(包括Fe(Ⅱ)/Fe(Ⅲ)-LDH和Mg/Fe-LDH)的非均相芬顿反应为主要研究背景,以有机染料甲基橙为目标对象,通过合成含有不同层间阴离子以及不同铁元素的LDH,利用结构中的铁与双氧水发生芬顿反应对甲基橙进行氧化降解,通过调节材料结构中铁的比例和种类以及层间阴离子的种类,探讨LDH中层间阴离子以及铁元素在非均相芬顿反应中的作用,并考察层间阴离子对LDH结构的影响。本文得的主要研究结果和结论如下所示:(1)通过共沉淀法在常温下合成十二烷基苯磺酸根(DBS-)为层间阴离子的Fe(Ⅱ)/Fe(Ⅲ)-LDH,即有机绿锈(DBS-GR),并通过XRD,FT-IR,SEM等方法对其进行结构表征,表明成功通过此种简单快速的方法合成了DBS-GR,其中有机阴离子的以单分子层平行倾斜的方式排列在金属层板间。有机绿锈在第一次芬顿降解反应中对甲基橙的去除效果都很好,速率很快,反应15 min去除率达到96%。去除原理为有机绿锈在降解甲基橙的过程中产生羟基自由基,进攻甲基橙分子的偶氮键,使其断裂分解,羟基自由基进一步分解小分子有机物,直到完全氧化成CO2和H2O分子。有机绿锈非均相芬顿体系能将芬顿反应的初始p H值扩展到中性左右进行反应,能达到和酸性条件一样的结果。(2)有机绿锈的氧化产物(DBS-GR*)在芬顿反应中对甲基橙的去除率依然能达到95%以上,而无机绿锈的氧化产物(SO4-GR*)对甲基橙仅有27.7%的去除率。DBS-GR*能循环多次使用,对高浓度的甲基橙也有很好的去除效果,在中性,对实际水处理有机污染物能避免调节p H值,循环四次后依然能有90%以上的去除率,且层状结构依然保持,是一种很有潜力的非均相芬顿反应材料。(3)比较有机绿锈和无机绿锈在不同氧化条件下结构的稳定性,无论是在自然条件下的缓慢氧化,在H2O2下的快速氧化还是在Fenton体系中的氧化,有机绿锈的氧化产物中依然有LDH的层状结构的存在,层板上Fe2+被原位氧化成Fe3+,氧化产物为DBS-插层的类针铁矿结构。而无机绿锈在三种氧化条件下结构都发生变化,原有的层状结构被破坏,氧化产物为针铁矿、磁铁矿或两者混合物。(4)不同金属比例以及陈化时间合成的Mg/Fe-LDH对甲基橙有不同的光芬顿效果,结构中铁离子的含量在其光芬顿反应降解甲基橙染料分子时起着至关重要的作用,随着铁离子含量的提高,光芬顿效果相应提高。LDH陈化时间越短,其晶体结构越不规整,暴露在外层的铁离子就越多,从而对甲基橙的吸附效果越好,光芬顿效果也相应提高。其中1:1未陈化的Mg/Fe-LDH的光芬顿效果最好速率最高,3h后达到80%的脱色率。Mg/Fe-LDH的光芬顿机理是固体表面非均相催化机理,在紫外光的照射下,LDH结构表面的三价铁离子被还原成二价铁离子,然后与吸附在表面的H2O2发生反应产生羟基自由基从而氧化甲基橙。
[Abstract]:With the rapid development of modern industry and agriculture, water pollution is becoming more and more serious, especially organic pollutants in water. In the treatment of organic pollutants in water, Fenton technology has been widely used because of its high efficiency and rapid reaction, because homogeneous Fenton must be under acidic reaction conditions to achieve better results. Layered double hydroxides (LDHs) is a kind of functional material with permanent positive charge and layered crystal structure of hydrotalcite. The structure and interchangeability of interlayer anions have potential applications in materials, chemical engineering, industrial catalysis, medicine and environmental sciences. The heterogeneous Fenton reaction of iron-containing LDH (including Fe (II) / Fe (III) - LDH and Mg / Fe-LDH) has been studied in this study. The methyl orange as the target dye was synthesized by the synthesis of different organic dyes. Interlayer anions and LDH with different iron elements were used to oxidize and degrade methyl orange by Fenton reaction between iron and hydrogen peroxide. The role of interlayer anions and iron elements in heterogeneous Fenton reaction was investigated by adjusting the proportion and type of iron in the structure of materials and the types of interlayer anions. The main results and conclusions are as follows: (1) Fe (II) / Fe (III) - LDH, i. e. organic green rust (DBS-GR), which is an interlayer anion of dodecylbenzenesulfonate (DBS-), was synthesized by coprecipitation at room temperature, and characterized by XRD, FT-IR and SEM. DBS-GR was synthesized by a simple and rapid method, in which the organic anions were arranged in the metal layers parallel to each other in a tilted manner. The removal efficiency of organic green rust to methyl orange was very good in the first Fenton degradation reaction. The removal rate was very fast, and the removal rate reached 96% in 15 minutes. Hydroxyl radicals are produced in the process, which attack the azo bond of methyl orange molecule and break it down. Hydroxyl radicals further decompose small molecules of organic matter until they are completely oxidized to CO2 and H2O molecules. Organic green rust heterogeneous Fenton system can extend the initial P H value of Fenton reaction to the neutral side or so, which can reach the same acidic condition. Results. (2) The removal rate of methyl orange by organic green rust oxidation product (DBS-GR*) was still above 95% in Fenton reaction, while that by inorganic green rust oxidation product (SO4-GR*) was only 27.7%. DBS-GR* could be recycled for many times and had good removal effect on high concentration of methyl orange, in neutral and in real water. Physical organic pollutants can avoid adjusting the P H value, and the removal rate can still be more than 90% after four cycles, and the layered structure is still maintained. It is a potential heterogeneous Fenton reaction material. (3) Comparing the structural stability of organic rust and inorganic rust under different oxidation conditions, whether under slow oxidation in natural conditions, in H2O2. The oxidation products of organic green rust still have the layered structure of LDH. Fe2+ is oxidized in situ to Fe3+ and the oxidation products are DBS-intercalated goethite-like structure. (4) Mg/Fe-LDH synthesized in different metal ratios and aging time has different photoFenton effect on methyl orange. The content of iron ions in the structure plays an important role in its photoFenton reaction to degrade methyl orange dye molecule. With the increase of iron ion content, photoFenton effect increases. The shorter the aging time of LDH, the more irregular the crystal structure and the more iron ions are exposed to the outer layer. Thus, the adsorption effect of methyl orange is better and the light Fenton effect is improved correspondingly. The mechanism of heterogeneous catalysis on the surface of LDH is that under ultraviolet irradiation, the trivalent iron ions on the surface of LDH structure are reduced to divalent iron ions, and then react with H2O2 adsorbed on the surface to produce hydroxyl radicals to oxidize methyl orange.
【学位授予单位】：上海大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703
本文编号：2182145
[Abstract]:With the rapid development of modern industry and agriculture, water pollution is becoming more and more serious, especially organic pollutants in water. In the treatment of organic pollutants in water, Fenton technology has been widely used because of its high efficiency and rapid reaction, because homogeneous Fenton must be under acidic reaction conditions to achieve better results. Layered double hydroxides (LDHs) is a kind of functional material with permanent positive charge and layered crystal structure of hydrotalcite. The structure and interchangeability of interlayer anions have potential applications in materials, chemical engineering, industrial catalysis, medicine and environmental sciences. The heterogeneous Fenton reaction of iron-containing LDH (including Fe (II) / Fe (III) - LDH and Mg / Fe-LDH) has been studied in this study. The methyl orange as the target dye was synthesized by the synthesis of different organic dyes. Interlayer anions and LDH with different iron elements were used to oxidize and degrade methyl orange by Fenton reaction between iron and hydrogen peroxide. The role of interlayer anions and iron elements in heterogeneous Fenton reaction was investigated by adjusting the proportion and type of iron in the structure of materials and the types of interlayer anions. The main results and conclusions are as follows: (1) Fe (II) / Fe (III) - LDH, i. e. organic green rust (DBS-GR), which is an interlayer anion of dodecylbenzenesulfonate (DBS-), was synthesized by coprecipitation at room temperature, and characterized by XRD, FT-IR and SEM. DBS-GR was synthesized by a simple and rapid method, in which the organic anions were arranged in the metal layers parallel to each other in a tilted manner. The removal efficiency of organic green rust to methyl orange was very good in the first Fenton degradation reaction. The removal rate was very fast, and the removal rate reached 96% in 15 minutes. Hydroxyl radicals are produced in the process, which attack the azo bond of methyl orange molecule and break it down. Hydroxyl radicals further decompose small molecules of organic matter until they are completely oxidized to CO2 and H2O molecules. Organic green rust heterogeneous Fenton system can extend the initial P H value of Fenton reaction to the neutral side or so, which can reach the same acidic condition. Results. (2) The removal rate of methyl orange by organic green rust oxidation product (DBS-GR*) was still above 95% in Fenton reaction, while that by inorganic green rust oxidation product (SO4-GR*) was only 27.7%. DBS-GR* could be recycled for many times and had good removal effect on high concentration of methyl orange, in neutral and in real water. Physical organic pollutants can avoid adjusting the P H value, and the removal rate can still be more than 90% after four cycles, and the layered structure is still maintained. It is a potential heterogeneous Fenton reaction material. (3) Comparing the structural stability of organic rust and inorganic rust under different oxidation conditions, whether under slow oxidation in natural conditions, in H2O2. The oxidation products of organic green rust still have the layered structure of LDH. Fe2+ is oxidized in situ to Fe3+ and the oxidation products are DBS-intercalated goethite-like structure. (4) Mg/Fe-LDH synthesized in different metal ratios and aging time has different photoFenton effect on methyl orange. The content of iron ions in the structure plays an important role in its photoFenton reaction to degrade methyl orange dye molecule. With the increase of iron ion content, photoFenton effect increases. The shorter the aging time of LDH, the more irregular the crystal structure and the more iron ions are exposed to the outer layer. Thus, the adsorption effect of methyl orange is better and the light Fenton effect is improved correspondingly. The mechanism of heterogeneous catalysis on the surface of LDH is that under ultraviolet irradiation, the trivalent iron ions on the surface of LDH structure are reduced to divalent iron ions, and then react with H2O2 adsorbed on the surface to produce hydroxyl radicals to oxidize methyl orange.
【学位授予单位】：上海大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703
【共引文献】
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