鐵系層狀雙金屬氫氧化物非均相類芬頓反應(yīng)及其機(jī)理研究
發(fā)布時(shí)間：2018-08-13 20:49
【摘要】：隨著現(xiàn)代工農(nóng)業(yè)飛速發(fā)展,水體污染越來越嚴(yán)重,其中尤以水中有機(jī)物的污染最為嚴(yán)重。在水中有機(jī)污染物的處理方法中,芬頓技術(shù)以處理效率高、反應(yīng)迅速快的特點(diǎn)被廣泛應(yīng)用,因?yàn)榫喾翌D必須在酸性的反應(yīng)條件下才能達(dá)到較好的處理效果,非均相芬頓法以其較寬的p H值范圍逐漸被重視,在水處理方面得到了廣泛的應(yīng)用。層狀雙金屬氫氧化物(Layered double hydroxides,簡(jiǎn)稱LDHs)是一種帶有永久正電荷的具有水滑石層狀晶體結(jié)構(gòu)的功能材料。由于其獨(dú)特的性質(zhì),層狀結(jié)構(gòu)以及層間陰離子的可交換性,在材料、化工、工業(yè)催化、醫(yī)藥和環(huán)境科學(xué)等領(lǐng)域具有潛在的應(yīng)用價(jià)值。本研究以含鐵LDH(包括Fe(Ⅱ)/Fe(Ⅲ)-LDH和Mg/Fe-LDH)的非均相芬頓反應(yīng)為主要研究背景,以有機(jī)染料甲基橙為目標(biāo)對(duì)象,通過合成含有不同層間陰離子以及不同鐵元素的LDH,利用結(jié)構(gòu)中的鐵與雙氧水發(fā)生芬頓反應(yīng)對(duì)甲基橙進(jìn)行氧化降解,通過調(diào)節(jié)材料結(jié)構(gòu)中鐵的比例和種類以及層間陰離子的種類,探討LDH中層間陰離子以及鐵元素在非均相芬頓反應(yīng)中的作用,并考察層間陰離子對(duì)LDH結(jié)構(gòu)的影響。本文得的主要研究結(jié)果和結(jié)論如下所示:(1)通過共沉淀法在常溫下合成十二烷基苯磺酸根(DBS-)為層間陰離子的Fe(Ⅱ)/Fe(Ⅲ)-LDH,即有機(jī)綠銹(DBS-GR),并通過XRD,FT-IR,SEM等方法對(duì)其進(jìn)行結(jié)構(gòu)表征,表明成功通過此種簡(jiǎn)單快速的方法合成了DBS-GR,其中有機(jī)陰離子的以單分子層平行傾斜的方式排列在金屬層板間。有機(jī)綠銹在第一次芬頓降解反應(yīng)中對(duì)甲基橙的去除效果都很好,速率很快,反應(yīng)15 min去除率達(dá)到96%。去除原理為有機(jī)綠銹在降解甲基橙的過程中產(chǎn)生羥基自由基,進(jìn)攻甲基橙分子的偶氮鍵,使其斷裂分解,羥基自由基進(jìn)一步分解小分子有機(jī)物,直到完全氧化成CO2和H2O分子。有機(jī)綠銹非均相芬頓體系能將芬頓反應(yīng)的初始p H值擴(kuò)展到中性左右進(jìn)行反應(yīng),能達(dá)到和酸性條件一樣的結(jié)果。(2)有機(jī)綠銹的氧化產(chǎn)物(DBS-GR*)在芬頓反應(yīng)中對(duì)甲基橙的去除率依然能達(dá)到95%以上,而無機(jī)綠銹的氧化產(chǎn)物(SO4-GR*)對(duì)甲基橙僅有27.7%的去除率。DBS-GR*能循環(huán)多次使用,對(duì)高濃度的甲基橙也有很好的去除效果,在中性,對(duì)實(shí)際水處理有機(jī)污染物能避免調(diào)節(jié)p H值,循環(huán)四次后依然能有90%以上的去除率,且層狀結(jié)構(gòu)依然保持,是一種很有潛力的非均相芬頓反應(yīng)材料。(3)比較有機(jī)綠銹和無機(jī)綠銹在不同氧化條件下結(jié)構(gòu)的穩(wěn)定性,無論是在自然條件下的緩慢氧化,在H2O2下的快速氧化還是在Fenton體系中的氧化,有機(jī)綠銹的氧化產(chǎn)物中依然有LDH的層狀結(jié)構(gòu)的存在,層板上Fe2+被原位氧化成Fe3+,氧化產(chǎn)物為DBS-插層的類針鐵礦結(jié)構(gòu)。而無機(jī)綠銹在三種氧化條件下結(jié)構(gòu)都發(fā)生變化,原有的層狀結(jié)構(gòu)被破壞,氧化產(chǎn)物為針鐵礦、磁鐵礦或兩者混合物。(4)不同金屬比例以及陳化時(shí)間合成的Mg/Fe-LDH對(duì)甲基橙有不同的光芬頓效果,結(jié)構(gòu)中鐵離子的含量在其光芬頓反應(yīng)降解甲基橙染料分子時(shí)起著至關(guān)重要的作用,隨著鐵離子含量的提高,光芬頓效果相應(yīng)提高。LDH陳化時(shí)間越短,其晶體結(jié)構(gòu)越不規(guī)整,暴露在外層的鐵離子就越多,從而對(duì)甲基橙的吸附效果越好,光芬頓效果也相應(yīng)提高。其中1:1未陳化的Mg/Fe-LDH的光芬頓效果最好速率最高,3h后達(dá)到80%的脫色率。Mg/Fe-LDH的光芬頓機(jī)理是固體表面非均相催化機(jī)理,在紫外光的照射下,LDH結(jié)構(gòu)表面的三價(jià)鐵離子被還原成二價(jià)鐵離子,然后與吸附在表面的H2O2發(fā)生反應(yīng)產(chǎn)生羥基自由基從而氧化甲基橙。
[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.
【學(xué)位授予單位】：上海大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：X703
本文編號(hào)：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.
【學(xué)位授予單位】：上海大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：X703
【共引文獻(xiàn)】
相關(guān)期刊論文 前6條
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