氮掺杂碳纳米孔材料催化过硫酸盐氧化直接红23染料废水

发布时间：2019-01-23 17:51

【摘要】：染料废水的处理是工业废水处理领域的难题之一。使用过硫酸盐氧化处理染料是一种有效的处理方式,具有处理速度快和矿化度好等优点。本研究采用自主合成的氮掺杂碳纳米孔材料作为非金属催化剂,催化过硫酸盐对目标染料——直接红23(DR23)的氧化。采用溶胶-凝胶法,选用较廉价易得的磷酸、蔗糖以及六亚甲基四胺等为碳源和氮源自主合成了一种氮掺杂碳纳米孔材料(NCN)。运用各种表征测试手段对材料的表观结构进行了详细的描述。结果显示:材料中成功掺杂了7.21 at.%的氮元素,主要包括吡啶型氮、吡咯型氮、石墨型氮和氧化态氮等四种氮官能团,其对应含量分别为:1.86 at.%、1.01 at.%、3.50 at.%和0.86 at.%。设置对照试验确定了氮掺杂碳纳米孔材料可以有效催化过硫酸盐(PS)氧化染料DR23。研究发现:当NCN使用浓度为200 mg/L,PS浓度为5 mmol/L,初始DR23浓度为50μmol/L时,DR23的去除满足一级动力学规律,一级反应速率常数为Kobs=3.36×10-2 min-1;R2=0.99,且在100 min内可实现了DR23和色度的完全去除,COD的去除率达到72%。产物分析结果表明,DR23中的偶氮键可以被迅速锻键,大分子的有机物污染物可以被氧化分解为小分子羧酸并最终被完全矿化为二氧化碳和水。NCN使用浓度的提高提高有助于体系中DR23的去除速度。对于含有50μmol/L DR23的染料废水中,NCN使用浓度在50 mg/L~1000 mg/L时,材料的使用浓度与反应一级动力学常数呈线性正相关。氧化剂PS投加量的增加亦有助于DR23的去除,但是在n(PS):n(DR23)300:1时,氧化剂的投加量的进一步提高不能使DR23的去除速度有效提升,反而大大增加成本。pH对NCN催化体系的影响较大,酸性条件对NCN的催化过程更加有利。对于碱性较大(pH10)的染料废水,提高PS的投加量是一种有效的方式。材料的回收简单易行,过滤、洗涤和烘干即可,其平均回收率为78.4%。重复使用的材料催化活性有些许下降,但是仍可以在短时间内完全去除DR23。自由基掩蔽实验的结果表明,NCN催化PS氧化DR23的过程遵循非自由基途径,即过硫酸根起到了氧化污染物的作用,而不是硫酸根自由基。结合材料结构分析,NCN良好的导电性可以通过强化电子传递实现对PS氧化DR23过程的催化。氮元素掺杂后带来的孤独电子对该过程有利。对比原始材料和重复使用材料中含氮官能团含量与材料对DR23氧化去除速率的关系,发现发现材料中N6和N-G含量与一级动力学常数间存在着良好的线性正相关(R20.95)。这说明,N6和N-G含量的提高有利于催化剂催化效能的提高。
[Abstract]:The treatment of dye wastewater is one of the difficult problems in the field of industrial wastewater treatment. Persulfate oxidation is an effective way to treat dyes, which has the advantages of fast treatment speed and good salinity. In this study, nitrogen-doped carbon nanoporous materials were used as non-metallic catalysts to catalyze the oxidation of direct red 23 (DR23) by persulfate. A nitrogen-doped carbon nano-porous material (NCN). Was synthesized by sol-gel method using cheap and readily available phosphoric acid, sucrose and hexamethylenetetramine as carbon and nitrogen sources. The apparent structure of the material was described in detail by various characterization methods. The results showed that the nitrogen elements of 7.21 at.% were successfully doped into the materials, including pyridine nitrogen, pyrrole nitrogen, graphite-type nitrogen and oxidized nitrogen. The corresponding contents were 1.86 at.%,. 1.01 at.%,3.50 at.% and 0.86 at.%. The results showed that nitrogen-doped carbon nanoporous materials can effectively catalyze persulfate (PS) oxidation of dye DR23.. It is found that when the concentration of NCN is 200 mg/L,PS and the initial concentration of DR23 is 50 渭 mol/L, the removal of DR23 satisfies the first-order kinetic law and the first-order reaction rate constant is Kobs=3.36 脳 10-2 min-1;. The total removal of DR23 and chromaticity can be achieved within 100 min, and the removal rate of COD can reach 722%. The results of product analysis show that the azo bond in DR23 can be rapidly forged. Organic pollutants of macromolecules can be oxidized to small carboxylic acids and then completely mineralized to carbon dioxide and water. The increase of NCN concentration is helpful to the removal rate of DR23 in the system. For dye wastewater containing 50 渭 mol/L DR23, when the concentration of NCN was 50 mg/L~1000 mg/L, there was a positive linear correlation between the concentration of NCN and the first-order kinetic constant of the reaction. The increase of the amount of oxidant PS also contributes to the removal of DR23, but the further increase of the dosage of oxidant can not improve the removal rate of DR23 effectively at n (PS): n (DR23: 300: 1. On the contrary, pH has a great influence on the catalytic system of NCN, and the acidic condition is more favorable for the catalytic process of NCN. It is an effective way to increase the dosage of PS in the dye wastewater with higher alkalinity (pH10). The recovery of the material is simple, filtration, washing and drying. The average recovery is 78.4%. The catalytic activity of the reused materials decreased slightly, but the DR23. could be removed completely in a short time. The results of free radical masking experiment show that the process of DR23 oxidation by PS catalyzed by NCN follows a non-free radical pathway, that is, persulfate acts as an oxidation pollutant rather than a radical sulfate radical. Combined with the analysis of material structure, the good conductivity of NCN can be used to catalyze the DR23 oxidation process of PS by enhancing electron transfer. The solitary electrons produced by nitrogen doping are beneficial to this process. By comparing the relationship between the content of nitrogen-containing functional groups and the removal rate of DR23 in the raw and reused materials, it was found that there was a good linear positive correlation between the content of N6 and N-G and the first-order kinetic constant (R20.95). It shows that the increase of N 6 and N G content is beneficial to the improvement of catalyst catalytic efficiency.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X788

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