【作者】 梁鹏；

【导师】 汪东风；

【作者基本信息】 中国海洋大学 ， 食品科学， 2013， 博士

【摘要】 我国是世界上地方性氟中毒较严重的国家之一。本研究以自然界第二大可再生资源壳聚糖为基体，利用稀土对其改性，制备得到一系列新型除氟剂，并对其制备条件、理化特征、吸附氟离子特性及吸附机理等进行了探讨。主要结果如下：⑴在La³⁺改性片状壳聚糖（CL）的基础上，首次利用成本较低的高La³⁺稀土改性片状壳聚糖，得到新型除氟剂CR，并研究了CL和CR对F-的吸附特性。结果表明：随着吸附时间的延长吸附容量增大，当反应时间为2h时，CL和CR达到吸附平衡状态；随pH逐渐增加，吸附容量呈下降趋势；当CL和CR的用量从0.5g/L增加到5.0g/L时，吸附百分比分别从19.28%和19.63%增加到93.51%和94.7%；当反应介质中F-初始浓度从1.25mg/L增加至20.0mg/L时，CL和CR的吸附容量呈快速增加趋势；饮用水中常见阴离子影响能力大小顺序为：CO₃^2- HCO₃-SO₄^2- Cl-NO₃^-；FTIR和XRD表征CL和CR，发现La³⁺和高La³⁺稀土与壳聚糖分子链中的氨基和羟基发生了配位反应，致使产物结晶度下降；CL和CR对F-的吸附等温线均符合Langmuir和Freundlich模型，为优惠吸附；拟二级动力学模型均能较好地描述实验结果，且CR拟二级动力学吸附速率常数较CL的大，表明CR在实际应用中更具有优势。⑵针对片状壳聚糖使用性能不稳定、不易与介质分离等缺陷，采用反相悬浮法合成了La³⁺和高La³⁺稀土改性壳聚糖树脂（CLB和CLRB），并探讨了制备条件的影响，包括La³⁺和高La³⁺稀土用量、反应pH值以及戊二醛用量等；FTIR分析表明，CLB和CLRB结构中形成了N-La³⁺和N-高La³⁺稀土配位键，壳聚糖分子链中的氨基或乙酰氨基与戊二醛发生了分子内或分子间希夫碱反应； DSC分析表明，CLB和CLRB的热稳定性高于结构中不含稀土离子的壳聚糖树脂（CB）；Langmuir和Freundlich等温线拟合效果较好，Qmax分别为3.70mg/g、5.88mg/g，均为优惠吸附；拟二级动力学模型拟合结果说明CLB和CLRB吸附F-过程由化学吸附控制；CLRB重复利用10次仍然具有较好的吸附性能。⑶为进一步提高壳聚糖树脂对F-的吸附容量，实验制备得到铈和高铈稀土改性壳聚糖树脂CCB和CCRB，评价了两种树脂对F-的吸附性能。结果表明：吸附容量受反应介质pH值、树脂用量、常见阴离子、F-初始浓度及反应温度的影响；Langmuir和Freundlich吸附等温线模型可较好地描述CCB和CCRB的吸附过程，饱和吸附容量Qmax分别为6.01mg/g、3.34mg/g，且随温度升高Qmax下降；控速步骤研究表明整个吸附过程由颗粒内扩散和液膜扩散联合控制。⑷为更易于树脂与反应介质分离、提高其使用效率和对F-的吸附容量，利用La³⁺和高La³⁺稀土改性磁性壳聚糖树脂得到MCLB和MCLRB，比饱和磁化强度分别为5.17emu/g和9.90emu/g；吸附实验表明，MCLB和MCLRB对F-具有较高的吸附容量；吸附等温线Langmuir和Freundlich模型均能较好地拟合实验结果，Qmax分别为20.53mg/g、22.35mg/g；均符合拟二级吸附动力学模型，吸附过程由化学吸附控制；MCLB和MCLRB结构中的Fe-O配位键可促进F-向树脂表面和内部移动，并与OH-发生离子交换作用，进一步提高F-吸附容量。⑸以上几种除氟剂用于处理模拟高氟饮用水时，均取得了良好的除氟效果，实验表明，用量优化后可使出水F-浓度均符合《生活饮用水卫生标准》；而且与传统除氟剂相比，本文所合成的几种稀土改性壳聚糖除氟剂，具有吸附容量高、吸附速率快、成本低廉、可多次重复利用且使用性能稳定等优点，有望进一步推广使用。⑹针对南极磷虾酶解液中F-浓度过高的问题，利用吸附容量高、成本低廉、吸附速率快的MCLRB，进行了脱氟工艺的初步研究，并取得了较好的效果。研究表明，MCLRB的用量为0.3g/25mL时，脱氟率达到67.27%，酶解液pH为2.0时，脱氟率为74.59%；MCLRB处理对酶解液的营养价值的影响研究显示，对蛋白质有一定的负面影响，损失率为16.67%；对其它营养成分的影响较小，总体来看，MCLRB可进一步应用于脱除南极磷虾酶解液中F-，为生产低F-浓度的磷虾酶解液产品做出一定的贡献。目前常用的治理F-浓度过高的方法存在诸多缺陷，采用稀土改性壳聚糖除氟剂治理含氟饮用水和含氟食品，不但能减轻氟化物对人体和环境的危害作用，还能充分利用虾、蟹加工废弃物制备的壳聚糖。因此，本研究工作的开展，具有一定的经济效益、社会效益和食品安全效益。更多还原

【Abstract】 The treatment methods for fluoride adsorption have been given more attentionrecently. In this study, a series of available fluoride adsorbents were prepared by rareearth-modified chitosan. The preparation, physicochemical characteristics, adsorptionproperties and mechanism of fluoride adsorbents were investigated and the drawingconclusions as follows:1A novel costeffective fluoride adsorbent, CR, was prepared for the first timeby rare earth-modified flake chitosan. The loading dosage of La³⁺and rare earth ontochitosan was discussed according to fluoride adsorption capacity. The results showthat the adsorption capacity was better when the ratio between La³⁺and chitosan was0.3:1.0. In addition, the adsorption capacity was increasing with contact timeincreased, but decreased evidently with pH improved. The adsorption rate wasincreased from19.28%,19.63%to93.51%and94.7%, respectively, when the dosageof adsorbents increased, the adsorption capacity was improved greatly with thefluoride initial concentration increased for adsorbents. The fluoride adsorptioncapacity was decreased with co-ions were existed in the same system, and the effectability obeyed the order of CO₃^2- HCO₃-SO₄^2- Cl-NO₃^-. The analysis of FTIR andXRD on CL, CR interpreted that rare earth metal ions were chelateed on chitosanmolecular chain with the functional groups. Thus, the crystalline was decreasedobviously compared to CS. The experiment results could be fitted well by adsorptionisotherm Langmuir, Freundlich, and pseudo second kinetic equation.2Since flake chitosan is not stable under acidic condition, novel fluorideadsorbents CLB and CLRB were prepared by La³⁺and high content of La³⁺rareearth-modified chitosan by inverse suspension method. The parameters of preparationprocess were studied including the dosage of rare earth, pH, and the dosage ofglutaraldehyde on the basis of fluoride adsorption capacity. The adsorbents werecharacterized by FTIR and DSC, there were two kinds of coordinate bonds as N-La³⁺and N-La³⁺rare earth which had high content of La³⁺existed in the structure ofadsorbents, respectively. Furthermore, schiff base reaction was carried out between the functional groups of-NH2,-OH and glutaraldehyde, so the thermostability of CLBand CLRB were higher than CB. The experiment data were fitted well by Langmuirand Freundlich isothermal model, the maximum adsorbent capacity was3.70mg/g,5.88mg/g, respectively. The whole adsorption process was controlled by chemicaladsorption according to the pseudo second kinetic equation. Finally, CLRB could bereused for10times with little loss.3In order to improve fluoride adsorption capacity, fluoride adsorbents of CCBand CCRB were prepared by cerium and high content of cerium rare earth modifiedchitosan resin. The adsorption properties for fluoride adsorption were discussed bytwo kinds of adsorbents. It was clearly to see that the adsorption capacity wasinfluenced greatly by the parameters of pH, dosage, co-ions and initial concentration,etc.. The experiment data were fitted well by istherm equation of Langmuir andFreundlich, and the maximum adsorption capacity was6.01mg/g,3.34mg/g,respectively. The fluoride adsorption capacity was decreased obviously when thereactive temperature was improved. Sorption kinetics was mainly controlled by twosteps of particle internal diffusion and liquid film diffusion.4Novel magnetic adsorbents were prepared using rare earth-modified chitosanwith Fe3O4nanoparticle, named MCLB and MCLRB, and the specific saturationmagnetization was5.17emu/g,9.90emu/g, respectively. Sorption experiments wereperformed by varying contact time, pH, presence of co-anions, etc.. The fluorideuptake onto two fluoride adsorption adsorbents obeyed both Freundlich and Langmuirisotherms, and the maximum adsorption capacity was20.53mg/g and22.35mg/g.Sorption kinetics was mainly controlled by pseudo-second-order. Fluoride could bemoved easily to the surface of adsorbents by the coordinate bond of Fe-O, and anionexchange is carried out between adsorbents and fluoride, and the fluoride adsorptioncapacity was improved eventually.5Various of fluoride adsorbents were applied in simulated drinking water withhigh content of fluoridel concentration, and achieved better effectiveness. However,the influence of adsorbents dosage on fluoride adsorption capacity was obvious Thefluoride in drinking water can be absorbed effectively and its concentration controlledwell after treatment by conducting adsorbents dosage. Comparison of the traditionalfluoride adsorbents, all of rare earth-modified chitosan adsorbents synthesized in thispaper, have higher fluoride adsorption capacity, faster adsorption rate, more costeffective, better reusable and much more stable, we hope these adsorbents can be used widely in future application.6The concentration of fluoride is higher in the enzymolysis liquid of Antarctickrill. Consequently, it is necessary to remove fluoride from enzymolysis liquid. In thisstudy, MCLRB was choosed as a fluoride adsorbent for its high adsorption capacity,costeffective, and better adsorption rate for removal fluoride. The defluoridationprocess was researched preliminarily, and the better results were obtained, eventually.The results show that the adsorption rate was getting to67.27%when the dosag ofMCLRB was0.3g/25mL, and getting to74.59%under the pH2.0of enzymolysisliquid. After MCLRB treatment, the variation of nutritional ingredients inenzymolysis liquid were investigated to some extent. There was a negative effect onthe content of protein after treatment compare to other nutritional ingredients. In oneword, MCLRB could be used as an effective fluoride adsorbent for removal excessfluoride from enzymolysis liquid to develop some meaningful food products byAntarctic krill with low level of fluoride concentration.All present methods for fluoride removal from drinking water have many owndisadvantages. Fluoride can be removed from drinking water by rare earth-modifiedchitosan, the fluoride is decreased obviously, and utilized the chitosan obtained fromseafood processing wastes. Consequently, those fluoride adsorbents synthesized inthis paper to remove fluoride, could be beneficial to economic, society, and foodsafety.更多还原