壳聚糖基碳复合材料的水热制备及其选择性吸附性能研究

发布时间：2018-03-22 04:17

本文选题：水热法　切入点：壳聚糖　出处：《安徽建筑大学》2015年硕士论文　论文类型：学位论文

【摘要】：碳质材料是一类富碳的物质,它除含碳元素以外,还含有丰富氧、氢元素元素。可通过水热碳化生物质制备得到。它有着优良的物理化学性质,在能源、环境以及生物工程等领域表现出潜在的价值。特别作为吸附剂使用时,其表面含有的功能基团,如羟基、氨基、羧基以及磺酸基等,能作为活性位点进行吸附,也为高效的选择性吸附提供了条件。壳聚糖是自然界含量丰富的甲壳素脱N-乙酰基的产物,含有丰富的羟基和氨基基团。然而,由于受溶解性的限制,很少用于水热过程制备碳质材料。本文报道利用壳聚糖为碳源水热制备碳质材料,并根据产物的结构特点研究了碳质材料对水污染物,特别是重金属离子的选择性吸附性能。具体内容如下:(1)采用一步水热制备了~830nm的α-Fe2O3@C微球的复合材料,其中碳质含量达80%。通过研究不同条件下产物的形貌结构特点,得出壳聚糖的加入量是决定产物形貌的关键因素。当没有壳聚糖加入到反应溶液中时,只能得到尺寸分布不均一的α-Fe2O3颗粒。壳聚糖加入后,会对产物形貌进行调控,促进产物尺寸均匀。当壳聚糖加入量为0.15g/50mL时,会得到大小尺寸相对均匀的α-Fe2O3颗粒。当0.50g/50m L壳聚糖加入反应体系时,几乎没有产物获得。当壳聚糖加入量为1.00g/50m L时,得到碳质微球为主的材料。进一步增加壳聚糖的量1.50g/m L,得到α-Fe2O3成分居多的α-Fe2O3@C微球。因此壳聚糖加入量不同,产物的形貌与结构也会发生变化。结合时间变量实验,得出碳质复合微球的形成机理:以α-Fe2O3模板,H+进行蚀刻,水热碳质微粒填补空位,最终形成微球形貌。重要的是,这种碳质材料具有氨基和羧基功能基团,表现出选择性吸附性能。调控不同pH条件,发现Cu(II)和Cr(VI)混合溶液中,微球对Cr(VI)在pH=2时有选择性。即pH=2时,微球对Cr(VI)的最大吸附量1.90mmol/g,对Cu(II)吸附量仅为0.022mmol/g,表现出选择性吸附Cr(VI)。当pH=3,4,5时,Cu(II)的吸附量随pH的增加而提高,最大吸附量为1.32 mmol/g,而Cr(VI)的吸附量会减小,最最小到1.33mmol/g。高pH条件下,微球不表现对Cr(VI)的选择性吸附。(2)以葡萄糖作为添加剂,加入到壳聚糖氯化铁水溶液,一步水热得到~830nm的α-Fe2O3@C空心球材料,碳质含量为6.50%。通过表征不同反应时间条件下的产物,发现空心球形成符合Ostwald熟化过程。此外壳聚糖的加入也起到很明显的作用,未加入壳聚糖时,只能得到大小形貌不规则的实心颗粒;加入0.15g壳聚糖后,发现产物尺寸变化均匀,同时有些颗粒变成空心结构;当壳聚糖加入量为0.5g时,才能够获得形貌一致大小均一的α-Fe2O3@C空心球。作为吸附剂,空心球表现出对痕量As(Ⅴ)(156.2μg/L)离子很好的去除能力,去除率高达98%。(3)采用尿素作为沉淀剂,壳聚糖为碳源制备了碳质与Fe3O4复合材料,碳质含量20.65%。结果显示碳质材料表面含有丰富的羧基官能团,在pH=9的水溶液中表现负电荷特性。作为吸附剂,它对亚甲基蓝(Methylene Blue;MB)表现快速去除能力,同时能选择性的将MB从MB与甲基橙(Methyl Orange;MO)混合溶液中移除。
[Abstract]:Carbonaceous material is a kind of carbon rich material, which in addition to the carbon element, also contains rich oxygen, hydrogen elements. Can be prepared by hydrothermal carbonization of biomass. It has excellent physical and chemical properties, in energy, environmental and biological engineering and other fields to show the potential value. Especially as adsorbent when in use, the surface containing functional groups, such as hydroxyl, amino, carboxyl and sulfonic groups, can be used as active sites for adsorption, but also provides the conditions for the selective adsorption efficiency. Chitosan is a natural product of the rich content of chitin by N- acetyl, rich in hydroxyl and amino groups. However, due to due to the limit of solubility, rarely used in the hydrothermal process for preparing carbonaceous materials. This paper reported the preparation of carbonaceous materials as carbon source heat prepared by chitosan, and studied the pollutants on water pollution of carbonaceous materials according to the structural characteristics of products, especially Is the performance of selective adsorption of heavy metal ions. The specific contents are as follows: (1) a -Fe2O3@C ~830nm composite microspheres were prepared by one-step hydrothermal method, the carbon content of 80%. by morphology and structure characteristics of the product under different conditions, adding that chitosan is a key factor in determining the morphology of the product. When not chitosan is added into the reaction solution, only -Fe2O3 alpha particle size distribution is not uniform. After adding chitosan, will regulate the morphology of the products, promote the products of uniform size. When the chitosan addition is 0.15g/50mL, will get alpha -Fe2O3 particles is relatively uniform size. When 0.50g/50m L chitosan addition reaction system, almost no product obtained. When the chitosan addition is 1.00g/50m L, get the carbonaceous materials. Further increase of microspheres of chitosan is 1.50g/m L, alpha -Fe2O3 are more The alpha -Fe2O3@C microspheres. Therefore chitosan with different adding amount, morphology and structure of the product can also be changed. Combined with the time variable experiment, the formation mechanism of the carbon microspheres: a -Fe2O3 template, H+ etching, hydrothermal carbonaceous particles fill the vacancy, and ultimately the formation of microspheres morphology. Importantly, this kind of carbonaceous materials with the amino and carboxyl functional groups showed adsorption selectivity. Regulation of different pH conditions, Cu (II) and Cr (VI) in the mixed solution of Cr (VI), microspheres have selectivity in pH=2. PH=2, Cr (VI) microspheres on the adsorption capacity of Cu (1.90mmol/g, II) the adsorption capacity is only 0.022mmol/g, showed the selective adsorption of Cr (VI). When pH=3,4,5, Cu (II) adsorption capacity increases with the increase of pH, the maximum adsorption capacity was 1.32 mmol/g, and Cr (VI) adsorption capacity decreases, the minimum to 1.33mmol/g. high pH conditions, not on the performance of the microspheres Cr (VI) selection Selective adsorption. (2) using glucose as an additive is added into the chitosan ferric chloride aqueous solution, one-step hydrothermal alpha -Fe2O3@C hollow sphere materials of ~830nm, carbon content is 6.50%. through the characterization of different reaction time conditions, found that the hollow spheres with Ostwald ripening process. This is also adding chitosan an obvious role, without the addition of chitosan, only solid particle size irregular morphology; adding chitosan 0.15g, found that the size of the product changes uniformly, and some particles into a hollow structure; when the chitosan addition is 0.5g, a -Fe2O3@C hollow sphere was able to obtain consistent morphology of uniform size as. Adsorbent, hollow spheres exhibit for the determination of As (V) (156.2 g/L) ion removal ability is very good, the removal rate of up to 98%. (3) using urea as precipitating agent, chitosan as the carbon source to prepare carbon and Fe3O4 composite 20.65%. results showed that the content of carbonaceous materials containing carboxylic acid rich surface carbonaceous material, negative charge characteristics in the aqueous solution of pH=9. It was used as the adsorbent for methylene blue (Methylene Blue; MB) showed rapid removal ability, and selective MB from MB and methyl orange (Methyl Orange; MO) to remove the mixture in the solution.

【学位授予单位】：安徽建筑大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB33

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