【作者】 邢云；

【导师】 李步海；

【作者基本信息】 武汉大学 ， 分析化学， 2009， 博士

【摘要】 现代工业的迅速发展产生了大量含重金属和染料的废水,因其污染物不可降解且易通过食物链在生物体内富集,对环境和人类生活构成了很大的威胁。在当前金属离子和染料废水的处理方法中,生物吸附法因操作简单、处理效率高而广泛应用。其中壳聚糖由于具有资源丰富、环境友好、吸附能力高、扩散性能好、高吸附性和选择性吸附、易恢复活性等优点,受到广泛关注。本论文在对壳聚糖结构特性及修饰改性研究现状和重金属及染料废水处理方法进行充分文献调研的基础上,对壳聚糖进行了接枝改性,并研究了其对重金属离子和阳离子染料的吸附行为。主要内容如下：1.选用戊二醛为交联剂,以液体石蜡为分散剂,Span 80为乳化剂,制备了壳聚糖微球。重点考察了交联剂用量对微球形貌的影响,并用扫面电镜、红外光谱进行了表征,用差示扫描量热仪及热天平测定了壳聚糖交联前后的热力学性质。研究了交联壳聚糖对Cd2+、Pb2+、Cu2+、Ag+、Co2+及Zn2+的吸附行为,并用XPS谱对吸附机理进行了探讨。结果表明,交联壳聚糖主要利用分子中的-NH2或-OH基团与重金属离子配位,从而吸附金属离子。壳聚糖交联后由于吸附活性基团-NH2被占据,吸附容量会有不同程度下降,但仍能够吸附低浓度的重金属离子溶液。2.以均苯四甲酸酐为修饰剂,在DMF中与交联壳聚糖微球混合,50℃水浴加热,磁力搅拌下,对交联壳聚糖微球表面进行修饰。BET氮气吸附法测定微球的比表面积降低,说明接枝后微球粒径增大。红外光谱和XPS谱表征结果显示均苯四甲酸酐成功的接枝到壳聚糖表面。讨论了修饰壳聚糖对六种金属离子Cd2+、Pb2+、Cu2+、Ag+、Co2+及Zn2+的吸附行为,并用Langmuir, Freundlich和Temkin模型对金属离子的吸附等温线进行模拟,结果表明Langmuir模型最适合描述此吸附过程。各个金属离子的吉布斯自由能ΔGo都为负数,说明金属离子在修饰壳聚糖微球上的吸附在实验条件下自发进行。选用0.2 mol·L-1 EDTA或5%硫脲-0.5 mol·L-1 HCl的溶液为洗脱剂,连续3次对上述六种金属离子进行吸附-解吸实验,循环三次吸附,解吸率基本都在90%以上。实际水样处理结果表明,修饰壳聚糖微球在实际废水处理中也是可以重复利用的,且金属离子的去除效果明显。3.制备了交联羧甲基壳聚糖,红外光谱及XPS谱表征结果显示,一氯乙酸成功的修饰在交联壳聚糖微球的表面。吸附等温线实验表明Langmuir吸附模型适合模拟此吸附过程,说明金属离子在交联羧甲基壳聚糖表面的吸附为单分子层吸附。动力学实验表明,准二级方程适合描述此吸附过程,而且吸附剂对三种金属离子都有着较高的初始吸附速率,处理效率大大提高。同其他吸附剂相比,该吸附剂具有较高的吸附容量,而且具有较好的再生能力,可反复使用。4.使用简单方法制备了聚胺酸修饰壳聚糖微球,采用红外光谱对聚胺酸修饰壳聚糖进行了表征,同时考查了pH值、吸附时间、浓度、离子强度及温度等因素对修饰壳聚糖吸附阳离子染料亚甲基蓝和中性红的影响,探讨了不同温度下吸附亚甲基蓝和中性红的热力学常数,结果表明,修饰壳聚糖对亚甲基蓝的吸附为放热反应,对中性红的吸附为吸热反应。实际染料废水处理结果表明,修饰壳聚糖具有一定的实际应用价值。5.采用热引发聚合法合成了聚甲基丙烯酸修饰壳聚糖微球,并用扫描电镜、红外光谱、XPS对修饰壳聚糖进行了表征。在选定的最佳条件下,修饰壳聚糖微球对四种阳离子染料：亚甲基蓝、中性红、孔雀石绿和结晶紫的最大吸附量分别为：1000.00、1062.15、471.70和1401.16 mg·g-1,具有较高的吸附容量。吸附剂的解吸实验表明,染料分子可以被有效的洗脱,所制备的TiO2溶胶容易通过离心与吸附剂分离,再生后吸附剂对染料吸附容量基本保持不变。酸性的TiO2溶胶作为染料吸附剂的再生剂具有很好的实际应用前景。更多还原

【Abstract】 A large number of wastewater containing heavy metals and dyes have been produced because of the rapid development of modern industry. The wastewater is non-degradable and easy to be concentrated in living bodies through food chain. It constitutes a great threat to environment and human life. Biosorption, as a new method, is a potential method for the removal of heavy metal ions and dyes due to the simple operation and high treatment efficiency. Among all kinds of adsorbents, chitosan attracted a wide spread attention, because of the abundant resources, high adsorption capacity, high adsorption and selective adsorption, etc. In this paper, we carried out the graft modification of chitosan and study of its adsorption behavior to metal ions and cationic dyes based on the full literature survey. The main work about the biosorption for metal ions and cationic dyes are summarized as follows:1. Chitosan microspheres was synthesized using glutaraldehyde as the crosslinker, paraffin as the dispersant and Span-80 as the emulsifier. The study focused on the effect of the dosage of crosslinker to the appearance of chitosan microsphere. The modified chitosan was characterized using SEM and FTIR analysis. The alteration of the microspheres’ thermal characteristic was measured by differential scanning calorimetry and thermal balance. The adsorption behavior of crosslinked chitosan to Cd2+, Pb2+, Cu2+, Ag+, Co2+ and Zn2+ was studied and the adsorption mechanism was discussed. The results indicate that the adsorption of crosslinked chitosan to the metal ions depend on the coordination of -NH2 or -OH with metal ions. The adsorption capacity of crosslinked chitosan decreased in different degrees for the active groups of -NH2 were occupied, but it still can adsorb metal ions solution with low concentration.2. Pyromellitic dianhydride (PMDA) grafted chitosan microspheres were prepared, and characterized by Scanning electric microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The changes in particle diameter of the microspheres before and after modification were also investigated by BET autosorb instrument, and the decreased surface area indicated that the particle diameter of the microspheres increased after the modification. The adsorption behavior of the modified microspheres to Cd2+, Pb2+, Cu2+, Ag+, Co2+ and Zn2+ was studied. The adsorption curves were fitted with the Langmuir, Freundlich and Temkin equations. The results showed that The Langmuir isotherm fitted best in the aforesaid equations. The negative values of standard free energy changes (△G°) of each metal ion showed that the adsorption reactions were spontaneous. The loaded biosorbent was regenerated by using 0.2 mol·L-1 EDTA or 5% thiourea-0.5 mol·L-1 HCl and could be used repeatedly at three times with little loss of uptake capacity. Good results were obtained when the modified microsphere was used to treat the real wastewater.3. In the paper, crosslinked carboxymethyl chitosan was prepared by a simple method. The presence of chloroacetic acid on the surface of chitosan was verified by FTIR and XPS. The adsorption curves were fitted well with Langmuir equation and the result indicated that the adsorption reaction of metal ions was adsorbed on the modified microspheres as monolayer. The kinetics for Pb2+, Cd2+ and Co2+ adsorption followed the pseudo-second-order kinetics, and the treatment efficiency improved greatly because of the higher initial absorbing rate. Compared with other adsorbents, the modified microspheres have the higher adsorption capacity and good regeneration ability, so it can be used repeatedly.4. A modified chitosan microspheres were prepared by grafting poly (amic acid), which was obtained via reaction of PMDA and L-arginine, onto the surface of chitosan. The modified chitosan was characterized using FTIR. The effect of pH, adsorption time, concentration of metal ions, coexisted ionic strength and temperature to the adsorption of methylene blue and neutral red were studied. Thermodynamic constants of methylene blue and neutral red adsorption under different temperature were discussed. The results showed that methylene blue adsorption was exothermic reaction, while the neutral red adsorption was endothermic reaction. The result of the treat of real wastewater showed the good practical application value of modified chitosan.5. In this study, the graft copolymerization of methacrylic acid onto chitosan was carried out in aqueous medium using potassium persulfate (PPS) as initiator. The obtained poly (methacrylic acid) modified chitosan was characterized by SEM, FTIR and XPS. Under the selected optimum conditions, the maximum adsorbing capacity of modified chitosan to four kinds of cationic dyes, methylene blue, neutral red, malachite green and crystal violet, were 1000.00,1062.15,471.70 and 1401.16 mg·g-1, respectively, which are higher than that of the unmodified chitosan. The loaded biosorbent was regenerated well by using acid titanium bioxide hydrosol with nanoparticles size. The adsorbent and the hydrosol could be easily separated by centrifugation. The adsorbent and the hydrosol could be reused with little loss of the ability, and it showed good potential to use in practical.更多还原