纳米微晶纤维素的氨基化改性及其吸附性能研究

发布时间：2018-11-28 20:23

【摘要】：近年来,纺织、塑料、造纸、印刷及食品等化学工业所排放的废水中含有的染料及重金属离子日益增加,不仅造成了环境污染,而且给人类的健康带来了巨大危害。因此,开发高效廉价的染料和重金属离子去除方法成为亟待解决的问题。由于具备低成本、对毒性污染物不敏感、流程简单灵活等优势,吸附法成为去除染料和重金属离子最常用的方法。最近,具有较大比表面积及众多吸附位点的纳米吸附剂受到越来越多的关注。本论文以纳米微晶纤维素(NCC)为原料,首先对其进行高碘酸盐氧化,制得二醛纳米纤维素(DANC)。然后,利用席夫碱反应将乙二胺接枝到DANC上,得到具有游离氨基的氨基纳米纤维素(ANCC)。最后,将ANCC用作阴离子染料及铬离子的吸附剂,并研究其吸附性能及机理。首先,采用硫酸水解法将漂白阔叶木硫酸盐浆(BHKP)水解,得到初始原料NCC。利用NaIO4氧化NCC,生成DANC,探讨了NaIO4用量、反应时间和反应温度对DANC醛基含量、Zeta电位、结晶指数及晶粒尺寸的影响,并通过FT-IR、XRD和TGA对产物性能进行表征。结果表明,随着NaIO4用量的增加,DANC的醛基含量逐渐增加；延长反应时间可以提高产物的醛基含量；在温度为40℃以下时,提高温度会促进氧化反应的进行,而当温度超过40℃,提高温度反而会抑制反应的进行。在NaIO4用量为6 mmol/g、反应时间为48 h、反应温度为40℃时,经过氧化改性所得的产物DANC的醛基含量为105.1%、Zeta电位为-19.5 mV。FT-IR分析表明,NCC经NaIO4氧化后,在其表面成功地引入了醛基。XRD分析表明,DANC的晶型没发生变化,仍保持纤维素-Ⅰ晶型。但与NCC相比,其结晶指数有所降低,且随着NaIO4用量的增加,结晶指数逐渐下降。热重分析结果显示,经NaIO4氧化后,DANC的热稳定性降低。随着NaIO4用量的增加,其初始降解温度逐渐降低。然后,利用乙二胺通过席夫碱反应对DANC进行氨基化改性,获得具有游离氨基的氨基纳米纤维素(ANCC)。探讨了乙二胺用量对产物得率、氨基含量和Zeta电位的影响,并通过FT-IR、XRD、TGA、AFM和元素分析对产物性能进行表征。结果表明,随着乙二胺用量的增加,ANCC的氨基含量和Zeta电位亦逐渐增加。FT-IR分析表明,DANC经氨基化改性后,成功地引入了氨基。标准茚三酮显色检测验证了产物中游离氨基的存在。XRD分析表明,ANCC的晶型没发生变化,仍保持纤维素-Ⅰ晶型。AFM图片显示,由于样品表面亲水性氨基的引入,ANCC的分散性有所提高。但与NCC相比,其粒径有所降低。最后,将ANCC用作阴离子染料和铬离子的吸附剂,探讨了ANCC用量、吸附时间及反应体系pH对吸附效果的影响,并对吸附等温线和吸附动力学进行了分析。结果表明,较大的ANCC用量、较长的吸附时间及酸性条件下,ANCC对酸性大红GR具有较好的吸附效果。当ANCC用量从0.5 g/L增加到1.0g/L时,脱色率由62%增长至100%；pH为4.7时,ANCC对酸性大红GR的脱色率为67.3%。ANCC对酸性大红GR的吸附符合Langmiur吸附等温模型；比较了ANCC对酸性大红GR(酸性染料)、刚果红4BS(直接染料)和活性嫩黄K-4G(活性染料)的吸附,发现ANCC对刚果红4BS的吸附能力最强。ANCC对三种阴离子染料的吸附动力学都遵循准二阶动力学模型。在pH为2的条件下,ANCC对铬离子具有较高的去除能力。ANCC对铬离子的吸附符合准二阶动力学模型和BET吸附等温模型。
[Abstract]:In recent years, the increasing of the dye and heavy metal ions contained in the waste water discharged from the chemical industries such as textile, plastics, paper making, printing and food, not only caused the environmental pollution, but also brought great harm to the human health. Therefore, the method of developing high-efficiency and cheap dye and heavy metal ion is a problem to be solved urgently. The method has the advantages of low cost, no sensitivity to toxic pollutants, simple and flexible flow, and the like, and the adsorption method is the most common method for removing the dye and heavy metal ions. Recently, nano-adsorbents with a large specific surface area and a large number of adsorption sites are attracting more and more attention. In this paper, the nano-microcrystalline cellulose (NCC) was used as the raw material, and then the periodate was oxidized to obtain the dialdehydes nano-cellulose (DANC). The ethylenediamine was then grafted onto the DANC using a schiff base reaction to give an amino nano-cellulose (ANCC) with a free amino group. Finally, ANCC was used as an adsorbent for anionic dye and chromium ion, and its adsorption properties and mechanism were studied. First, the bleached broad-leaved wood kraft pulp (BHKP) is hydrolyzed by a sulfuric acid hydrolysis method to obtain the initial raw material NCC. The effects of NaIO4 dosage, reaction time and reaction temperature on the content of DANC, Zeta potential, crystallization index and grain size were discussed by using NaIO4 to oxidize NCC, and the product properties were characterized by FT-IR, XRD and TGA. The results show that, with the increase of the amount of NaIO4, the aldehyde group content of the DANC is increased gradually, the reaction time can be prolonged, the aldehyde group content of the product can be increased, and when the temperature is lower than 40 DEG C, the oxidation reaction can be carried out, and when the temperature is more than 40 DEG C, Increasing the temperature will instead inhibit the reaction. The aldehyde group content of the product DANC obtained after the oxidation modification was 105.1% and the Zeta potential was-19.5mV. FT-IR analysis showed that the NCC was successfully introduced into the aldehyde group after NaIO4 oxidation. The XRD analysis shows that the crystal type of the DANC is not changed, and the cellulose-I-crystal is still maintained. However, compared with NCC, the crystallization index decreased, and the crystallization index decreased with the increase of the amount of NaIO4. The results of the thermal re-analysis show that the thermal stability of the DANC decreases after NaIO4 oxidation. As the amount of NaIO4 increases, its initial degradation temperature is gradually reduced. The DANC was then amino-modified with ethylenediamine by a schiff base reaction to obtain an amino nano-cellulose (ANCC) having a free amino group. The effects of the amount of ethylenediamine on the product yield, the amino content and the Zeta potential were discussed, and the product properties were characterized by FT-IR, XRD, TGA, AFM and elemental analysis. The results showed that the amino content and Zeta potential of ANCC were also increased with the increase of the amount of ethylenediamine. The FT-IR analysis showed that the amino group was successfully introduced after the modification of the DANC. The presence of free amino groups in the product is verified by the development of standard triketone. The XRD analysis shows that the crystal type of ANCC is not changed, and the cellulose-I-crystal is still maintained. The AFM picture shows that the dispersibility of ANCC is improved due to the introduction of hydrophilic amino groups on the surface of the sample. but its particle size is reduced as compared to NCC. In the end, ANCC was used as an adsorbent of anionic dye and chromium ion, and the influence of ANCC dosage, adsorption time and pH of reaction system on the adsorption effect was discussed, and the adsorption isotherm and adsorption kinetics were analyzed. The results show that ANCC has a good adsorption effect on the acid big red GR under the condition of long adsorption time and acid condition. When the amount of ANCC was increased from 0.5 g/ L to 1. 0g/ L, the decoloration rate was increased from 62% to 100%, and the decoloration rate of the ANCC to the acid red GR was 67.3% when the pH was 4.7. The adsorption of the ANCC on the acid large red GR was in accordance with the Langmuir adsorption isotherm model, and the ANCC was compared with the acid large red GR (acid dye). The adsorption of red 4BS (direct dye) and active light yellow K-4G (reactive dye) showed that the adsorption capacity of ANCC to the red 4BS was the strongest. The adsorption kinetics of the ANCC to the three anionic dyes follow the quasi-second-order kinetic model. and under the condition of pH 2, the ANCC has higher removal capacity for chromium ions. The adsorption of chromium ions by ANCC is in accordance with the quasi-second-order kinetic model and the BET adsorption isotherm model.
【学位授予单位】：齐鲁工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O647.33;X703

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