|Place of Conferral||北京|
|Keyword||棉酚 鞣花酸 分子印迹 溶胶凝胶表面印迹 选择性识别与吸附|
棉花是一种重要的农作物，棉酚是从棉籽里提取出来的一种有毒的多酚类化合物。棉籽饼粕作为棉籽榨油后的副产物，它的蛋白质含量很高并且价廉易得，已成为畜牧和水产养殖业中一种必需的蛋白饲料资源，但是棉酚的毒性严重限制了它的应用。因此，去除棉酚的研究意义重大。鞣花酸是一种天然的多酚类黄酮，具有抗氧化、抗癌、抗衰老、美白皮肤的功效，被广泛应用于医药、保健食品及化妆品中。传统的纯化鞣花酸的方法费时费力，选择性较差，因此，设计和合成对鞣花酸具有高选择性的新型吸附功能材料意义重大。分子印迹聚合物是一种对目标分子具有高亲和性和高选择性的功能材料，本论文利用分子印迹技术的手段，分别设计并制备了几种不同的对目标分子具有选择性吸附的材料，并成功地应用于目标分子的去除，具体研究内容如下：（1）棉酚分子印迹聚合物的合成及对棉酚选择性识别和吸附的评价以棉酚（gosypol）为模板分子，选取甲基丙烯酸二甲氨基乙酯（DMAEMA）为功能单体，二甲基丙烯酸乙二醇酯（EGDMA）为交联剂，二氯甲烷（CH2Cl2）为致孔剂，偶氮二异丁腈（AIBN）为引发剂，通过本体聚合的方法，热引发聚合的方式，设计和合成了棉酚分子印迹聚合物（MIP）。通过扫描电子显微镜（SEM）和氮气吸脱附仪表征了材料的表面形貌和微结构。通过静态吸附实验评价了分子印迹聚合物对棉酚的吸附行为。对吸附实验数据进行非线性拟合，结果显示MIP对棉酚的吸附动力学较好地符合准二级动力学模型，MIP对棉酚的吸附等温线符合Freundlich吸附等温方程。对吸附等温实验进行Scatchard分析显示，MIP内部的结合位点是不均匀的，形成了两种不同类型的结合位点，包括低亲和力的结合位点，此类位点的最大吸附容量是252 mg.g-1； 高亲和力的结合位点，它的最大吸附容量为632 mg.g-1。吸附实验也表明了与非印迹聚合物（NIP）相比，MIP对模板分子棉酚具有很好的选择性。而且，该材料在重复利用5次之后，对棉酚的吸附容量仍能保持在90%以上，表明该材料可以重复使用数次，循环使用性能佳。以上结果显示制备得到的MIP是一种很有应用潜力的功能材料，能够实现对棉酚的选择性吸附。（2）溶胶-凝胶表面分子印迹聚合物的制备及对棉酚特异性识别研究把表面分子印迹技术和溶胶-凝胶方法相结合，设计了棉酚特异性识别功能材料。以棉酚为模板分子，三氨丙基三乙氧基硅烷（APTES）为功能单体，四乙氧基硅烷（TEOS）为交联剂，丙酮为溶剂，硅胶为载体制备了棉酚MIP。所得的分子印迹聚合物通过傅里叶红外（FT-IR）、热重分析（TGA）、扫描电子显微镜（SEM）和氮气吸脱附法这一系列表征手段探究了材料的形貌、结构和性质。棉酚溶液的吸附实验结果显示MIP对棉酚的吸附能力远远高于NIP和载体硅胶对棉酚的吸附。对MIP来讲，该材料可在40 min内达到对棉酚的吸附平衡，最大吸附容量高达120 mg.g-1，并且选择性吸附实验结果得出MIP对棉酚的选择性因子相对于两种模板类似物（鞣花酸和槲皮素）分别是2.09和2.61，表明MIP对棉酚具有高选择性和特异性识别。MIP对棉酚的吸附动力学和吸附等温曲线更好地适用于准二级动力学模型和Freundlich吸附等温模型。除此之外，MIP展示了优秀的重复利用性和稳定性，表现在材料经过10次吸附-解吸附循环后，MIP对棉酚的吸附容量只有轻微的降低（5.5%）。所有结果表明了合成的MIP可以作为一种很好的选择性去除棉酚的吸附材料。（3）硅胶载体的尺寸和形状对溶胶-凝胶表面分子印迹聚合物在选择性吸附棉酚中的影响以不同形状和不同尺寸的硅胶为载体，探究了不同的硅胶载体对表面分子印迹聚合物识别性质的影响。通过表面印迹技术和溶胶-凝胶过程在硅胶基质上合成了用于选择性识别和吸附棉酚的MIPs，其中以棉酚为模板分子，选取三氨丙基三乙氧基硅烷（APTES）和四乙氧基硅烷（TEOS）分别作为反应的功能单体和交联剂。MIPs分别通过傅里叶红外（FT-IR）、扫描电子显微镜（SEM）和BET比表面积分析法表征了材料的表面形貌和结构。结果表明硅胶表面的印迹聚合物层有助于模板分子的去除和再结合，因此表现出较快的吸附动力学。与以形状不规则、粒径分布较宽的硅胶为载体合成的MIPs相比，形状为规则球形，粒径均一的硅胶载体对应的MIPs印迹因子更高，印迹效果更好。并且以形状规则的粒径较大（60 μm）的球形硅胶为载体合成的MIP比以粒径较小（5 μm和15 μm）的球形硅胶为载体合成的MIP显示出更高的吸附容量。对以60 μm的球形硅胶为载体合成的MIP来讲，该材料表现出较快的吸附动力学，可在10 min时达到吸附平衡，材料的饱和吸附容量可达204 mg.g-1。与棉酚的结构类似物鞣花酸（IF=1.13）和槲皮素（IF=1.20）相比，此材料对棉酚（IF=2.20）的选择性较高。该MIP对棉酚的吸附数据与准二级吸附动力学模型和Freundlich吸附等温模型有很好的相关性，这表明发生了化学速控的和多层的吸附。并且此MIP的再生性优良，在经过6次重复使用后，MIP对棉酚的吸附容量仅仅损失了6%，表明该材料在棉酚的识别和吸附方面有很好的应用价值。（4）溶胶-凝胶表面分子印迹功能材料的合成及其选择性吸附鞣花酸的研究结合溶胶-凝胶方法和表面分子印迹技术，以二氧化硅为载体，鞣花酸为模板分子，3-氨丙基三乙氧基硅烷为功能单体，四乙氧基硅烷为交联剂，在室温下合成了鞣花酸分子印迹聚合物（MIP）。通过扫描电镜表征了MIP的表面形貌。通过静态吸附实验评价了MIP对鞣花酸的吸附行为，结果显示，MIP对鞣花酸可在40 min内达到吸附平衡，印迹因子为2.68，饱和吸附容量可达70 mg/g；与非印迹聚合物相比，MIP对鞣花酸具有高选择性和特异识别性。对吸附数据进行非线性拟合结果显示，MIP对鞣花酸的吸附动力学较好地符合准二级动力学模型，MIP对鞣花酸的吸附等温线较好地符合Langmuir等温方程。另外，该材料在经过5次循环利用之后，对鞣花酸的吸附容量仍能保持在90%以上，表现了出色的重复利用性能。所有结果表明，合成的MIP能够作为一种良好的选择性吸附鞣花酸的功能材料，有望应用在复杂基质中鞣花酸的分离和纯化。
Cotton is one of the most important agricultural crops. Gossypol is a toxic polyphenolic compound indigenous to the seeds of cotton plants. And cottonseed meal is becoming an important part of high-quality yet inexpensive protein feed source for animal husbandry and aquaculture. However, the presence of poisonous gossypol severely restricted its application. Thus, removal of gossypol in cottonseed products has become significantly important.Ellagic acid is a natural polyphenolic flavonoid, which possesses antioxidative activity, anti-cancer properties, anti-aging effect and whitening efficiency on human skin. It has been applied extensively in the drugs, health food and cosmetics. Traditional methods for ellagic acid purification undergo drawbacks such as high consumption of time, labor and poor selectivity toward ellagic acid. Thus, it is significantly important to design and synthesize novel functional materials as adsorbents which feature high selectivity for ellagic acid.Molecularly Imprinted Polymers (MIPs) are functional materials for a target molecule with high affinity and selectivity. In this dissertation, some different type of materials based on molecular imprinting technique (MIT) for selective adsorption of target molecule were designed and prepared, then successfully applied in removal of target molecule. The study is as follows:(1) Preparation and evaluation of molecularly imprinted polymer for selective recognition and adsorption of gossypolMolecularly imprinted polymers (MIPs) were designed and prepared via bulk thermal polymerization with gossypol as the template molecule, dimethylaminoethyl methacrylate (DMAEMA) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, dichloromethane as the porogen and 2, 2＇-Azobis-iso-butyronitrile (AIBN) as the initiator. The morphology and microstructures of MIPs were characterized by scanning electron microscope (SEM) and Brunauer–Emmett–Teller (BET) surface areas. Static adsorption tests were performed to evaluate adsorption behavior of gossypol by the MIPs. It was found that adsorption kinetics and adsorption isotherms data of gossypol by MIPs were fit well with pseudo-second-order model and Freundlich model,respectively. Scatchard analysis showed that heterogeneous binding sites were formed in the MIPs including lower-affinity binding sites with the maximum adsorption (Qmax) of 252 mg g-1 and higher-affinity binding sites with the Qmax of 632 mg g-1. Binding studies also revealed that MIPs had favorable selectivity towards gossypol compared with non-imprinted polymers (NIPs). Furthermore, adsorption capacity of MIPs maintained above 90% after five regeneration cycles, indicating MIPs were recyclable and could be used multiple times. These results demonstrated that prepared MIPs could be a promising functional material for selective adsorption of gossypol. (2) Sol-gel surface molecular imprinted polymers for the specific recognition of gossypolFunctional materials for the specific recognition of gossypol were designed by combining surface imprinting technique with a sol-gel polymerization process. Molecularly imprinted polymers (MIPs) were prepared using gossypol as the template molecule, 3-aminopropyltriethoxysilane (APTES) as the functional monomer, tetraethoxysilicane (TEOS) as the cross-linker and silica gel as the support. The as-prepared MIPs were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and nitrogen adsorption-desorption techniques to probe their morphology, structure and property. The solution binding studies exhibited that the MIP had higher adsorption capacity towards gossypol than it control NIP and the support silica gel. For the MIP, the adsorption equilibrium could be reached in 40 min; the maximum adsorption capacity was as high as 120 mg g-1, and selectivity coefficients for gossypol relative to ellagic acid and quercetin were 2.09 and 2.61, respectively, indicating outstanding specificity and high selectivity towards target gossypol. Pseudo-second-order kinetic model and the Freundlich isotherm model were more applicable for the adsorption kinetics and adsorption isotherm of gossypol binding. In addition, the MIP showed excellent stability and reusability. The adsorption capacity of the MIP only showed a slight decrease (5.5%) after ten adsorption-desorption cycles. All results suggested that the prepared gossypol-MIP could serve as a promising adsorbent material for selective recognition and removal of gossypol. (3) The influence of size and shape of silica support in sol-gel surface molecular imprinting for selective adsorption of gossypolThe influence of the various silica gel supports with different shape and size on the recognition properties of the surface molecular imprinted polymers (MIPs) was investigated. MIPs for selective recognition and adsorption of gossypol were synthesized via sol-gel process with surface imprinting technique on silica gel substrates. 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilicane (TEOS) were chosen as the functional monomer and the cross-linker. The morphology and structure of the gossypol-MIPs were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and a standard Brunauer–Emett–Teller (BET) analysis. Results indicated that the surface imprinting polymer layer facilitated the removal and rebinding of the template, and thus achieved fast binding kinetics. Compared with the MIPs prepared on the silica of irregular shape and a broad particle size distribution, the MIPs using silica of regular spherical shape and uniform size showed higher imprinting factors, and the MIP made with relative larger size (60 μm) spherical silica demonstrated higher adsorption capacity compared to the MIPs made with smaller size spherical silica. The MIP prepared with 60 μm spherical shape silica featured a fast adsorption kinetic of 10 min and a saturated adsorption capacity of 204 mg g-1. The gossypol-MIP had higher selectivity (IF=2.20) for gossypol over its structurally similar analogues ellagic acid (IF=1.13) and quercetin (IF=1.20). The adsorption data of the MIPs were well correlated to the pseudo-second-order kinetic model and the Freundlich isotherm model. Results implied that chemical adsorption dominated and multilayer adsorption occurred. The MIP exhibited an excellent regeneration performance, and the adsorption capacity of the MIP for gossypol only decreased by 6 % after 6 reused cycles showing good application potential for the recognition and adsorption of gossypol.(4) Preparation of functional materials based on sol-gel surface molecular imprinting for selective adsorption of ellagic acidMolecularly imprinted polymer (MIP) was prepared using silica gel as the support, gossypol as the template molecule, 3-aminopropyltriethoxysilane (APTES) as the functional monomer, tetraethoxysilicane (TEOS) as the cross-linker at room temperature. The surface morphology of MIP was characterized by scanning electron microscope (SEM). Static adsorption tests were performed to evaluate adsorption behavior of MIP for ellagic acid. The results indicated that the adsorption equilibrium of MIP could be reached in 40 min, the imprinting factor was 2.68, the saturated adsorption capacity was as high as 70 mg/g. Compared to non-imprinted polymer (NIP), the MIP exhibited high selectivity and specific recognition toward ellagic acid. It was found that adsorption kinetics and adsorption isotherms data of MIP were fit well with pseudo-second-order kinetic model and Langmuir isotherm model by nonlinear regression, respectively. Besides, adsorption capacity of MIP maintained above 90% after five regeneration cycles, indicating outstanding reusability of MIP. All the results demonstrated that prepared MIP could be severed as an excellent functional material for selective adsorption of ellagic acid and had good application potential for the separation and purification of ellagic acid in complex matrix.
|郅轲轲. 棉酚分子印迹聚合物的设计合成及性能研究[D]. 北京. 中国科学院大学,2018.|
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