【作者】 王利军；

【导师】 王双飞；

【作者基本信息】 广西大学 ， 制糖工程， 2013， 博士

【摘要】 结合广西实际,利用广西优势农业资源,研发出一些成本低、效果好、无二次污染的重金属治理方法具有重要的战略意义和现实意义。制糖工业是广西的特色产业和支柱产业之一,其主要副产品蔗渣中半纤维素含量约占28%-35%,通过化学改性可使半纤维素侧链衍生出高密度的羧基,使其具备优良的金属螯合作用。本论文研究了微波-碱法提取半纤维素的工艺,对蔗渣半纤维素进行了成分分析；采用羧基化改性和两性改性两种方法对蔗渣半纤维素进行化学改性,并对其改性前后的结构与热稳定性进行表征；分别以两种方法改性后的蔗渣半纤维素作为吸附剂,通过吸附试验考察了其对Cu2+、Pb2+、Cd2+的吸附效果,并对吸附动力学和热力学进行了研究。1.采用微波-碱法提取蔗渣半纤维素,考察了液固比(每克蔗渣对应加水的毫升数)、NaOH用量(每克蔗渣对应加入NaOH的克数)、处理时间和微波功率等因素对对蔗渣半纤维素提取率的影响,得到最佳提取工艺条件为：液固比25ml/g、NaOH用量2.0g/g、处理时间20min、微波功率1200W。采用气相色谱法对蔗渣半纤维素进行了成分分析,结果表明,蔗渣半纤维素属于聚木糖类半纤维素,主要单糖组成为D-木糖、D-阿拉伯糖、L-树胶醛糖、D-半乳糖醛酸、D-半乳糖和D-甘露糖。2.采用将羧基引入蔗渣半纤维素的方法将其进行改性,考察了丁二酸酐用量、N-溴代丁二酰亚胺用量、反应时间、反应温度等因素对羧基化改性的影响,结果表明,对1g干燥后的蔗渣半纤维素进行羧基化改性,在丁二酸酐用量为3g、N-溴代丁二酰亚胺用量为O.1g、反应时间为6h、反应温度为70℃时,可制得较为满意的羧基化改性蔗渣半纤维素。采用红外光谱、核磁共振、扫描电镜、热分析仪分别对蔗渣半纤维素羧基化改性前后进行了表征,结果表明,本研究采用的改性方法成功的将羧基引入蔗渣半纤维素中,并且羧基化改性后蔗渣半纤维素的分子结构和形态发生了变化,羧基化改性后半纤维素的热稳定性下降。3.采用改性剂对蔗渣半纤维素进行两性改性,考察了改性剂用量、NaOH用量、反应温度、反应时间、改性次序等因素对两性改性的影响,结果表明,对1g干燥后的蔗渣半纤维素进行阳离子化改性,在3-氯-2-羟基丙基三甲基氯化铵用量为0.3g、NaOH用量为O.1g、反应时间为2h、反应温度为60℃时,可得到较为满意的阳离子化改性产物；对1g干燥后的蔗渣半纤维素进行阴离子化改性,在一氯醋酸用量为0.4g、NaOH用量用量为0.3g、反应时间为2h、反应温度为80℃时,可得到较为满意的阴离子化改性产物；按照先阴离子化再阳离子化的改性次序得到的两性改性产物效果更好。采用红外光谱、核磁共振、扫描电镜、热分析仪对两性改性的蔗渣半纤维素进行了表征,结果表明,本研究采用的改性方法成功的将羧基和季铵基引入蔗渣半纤维素中,并且发现两性改性后蔗渣半纤维素的分子结构和形态发生了变化,两性改性后蔗渣半纤维素的热稳定性下降。4.使用羧基化蔗渣半纤维素吸附Cu2+、Pb2+和Cd2+离子,考察了pH值对吸附容量的影响,结果表明,吸附Cu2+最适pH值为5.5,吸附Pb2+最适pH值为5.5,吸附Cd2+最适pH值为7.5。羧基化蔗渣半纤维素对Cu2+、Pb。+和Cd2+离子的吸附容量随着重金属初始浓度的增加而增大,浓度持续增高则吸附容量的变化量逐渐减小。通过热力学研究表明,Freundlich等温吸附模型可以很好的描述羧基化蔗渣半纤维素吸附Cu2+、Pb2+和Cd2+离子的过程,吸附反应焓变△H<0、吉布斯自由能△G<0,表明吸附反应是放热反应,可以自发进行。通过动力学研究表明,拟二级动力学模型可以描述羧基化蔗渣半纤维素对Cu2+、Pb2+和Cd2+离子的吸附动力学过程,饱和吸附容量理论值qe,cal分别为19.34mg/g.59.52mg/g和29.41mg/g,在温度为293K下；拟二级动力学方程分别为dqt/dt=0.0623(19.34-qt)2、dqt/dt=0.0237(59.52-qt)2和dqt/dt=0.0433(29.41-qt)2。5.使用两性蔗渣半纤维素吸附Cu2+、Pb2+和Cd2+离子,考察了pH值对吸附容量的影响,结果表明,吸附Cu2+最适pH值为6.5,吸附Pb2+最适pH值为6,吸附Cd2+最适pH值为7.5。两性蔗渣半纤维素对Cu2+、Pb2+和Cd2+离子的吸附容量随着重金属初始浓度的增加而增大,浓度持续增高则吸附容量的变化量逐渐减小。通过热力学研究表明,Freundlich等温吸附模型可以很好的描述两性蔗渣半纤维素吸附Cu2+、Pb2+和Cd2+离子的过程；吸附反应焓变△H<0、吉布斯自由能△G<0,表明吸附反应是放热反应,可自发进行。通过动力学研究表明,拟二级动力学模型可以描述两性蔗渣半纤维素对Cu2+、Pb2+和Cd2+离子的吸附动力学过程,饱和吸附容量理论值qe,cal分别为26.45mg/g、65.79mg/g和36.23mg/g;在温度为293K,拟二级动力学方程分别为dqt/dt=0.00936(26.45-qt)2、dqt/dt=0.0231(65.79-qt)2和dqt/dt=0.0428(36.23-qt)2。更多还原

【Abstract】 Combined with the actual conditions of Guangxi, the research on the control of heavy metal pollution with low-cost, effective, and no second pollution has important practical and strategic significance. Cane-sugar industry is one of the distinctive pillar industries in Guangxi, the bagasse with28%～35%of hemicellulose is the main by-product. High density carboxyl would be derived from the side-chain of hemicellulose via chemical modification, and the derivative is capable of metal chelating. This study researched on the extraction of hemicellulose by Microwave-Alkali Method, the component of hemicellulose was analyzed; the hemicellulose was modified by carboxylation and amphoteric modification, and the structure and thermophysical property were characterized before and after chemical modification; the modified production was used to test the adsorption effective of Cu2+、Pb2+、Cd2+as adsorbent, the kinetic and thermodynamic characteristics of adsorption was also studied.1. Extracion of hemicelluloses from sugarcane bagasse under microwave irradiation was studied in this paper. The effect of liquid to solid ratio (V (water):m (stover)), alkali consumption (m(NaOH):m (stover)), time, microwave power, and temperature on the extraction yield of hemicelluloses was investigated. The optimal processing parameters were:liquid to solid ratio of25ml/g, alkali consumption of2.0g/g, time of20min, and microwave power of1200W. The obtained hemicelluloses was qualitatively analyzed by gas chromatography, and results show that, sugarcane bagasse hemicelluloses is a kind of xylan hemicelluloses, mainly consisting of simple sugars like D-xylose, D-arabinose, L-arabinose, D-galacturonic acid, D-galactose and D-mannose.2. Carboxyl is adopted to modify the properties of the sugarcane bagasse hemicelluloses, and effects of the succinic anhydride, N-bromination succinic imide, reaction time and reaction temperature on the modification were studied. The result shows that under the conditions of succinic anhydride for3g, N-bromination succinic imide for0.1g, reaction time for6h and reaction temperature at70℃, modified hemicelluloses can be obtained more satisfied from the1g dried sugarcane bagasse hemicelluloses. Characterization of the hemicelluloses was respectively done through the FT-IR, nuclear magnetic resonance (NMR), thermal analyzer and scanning electron microscopy (SEM) before and after the experiment, and results show that the structure and form of sugarcane bagasse hemicelluloses were changed after the carboxyl modification, and thermal stability was also found declined.3. Modifiers were applied to make amphoteric modification on sugarcane bagasse hemicelluloses, and examined the amount of modifiers, the amount of Sodium hydroxide, reaction temperature, reaction time, the order of modification and other factors on the impact of gender modification, the result shows that, when making cationic modification on the one gram of dried sugarcane bagasse hemicelluloses, we can obtain more satisfactory cationic modified product under the conditions that the amount of3-chloro-2-hydroxypropyl trimethyl ammonium chloride is0.3g, the amount of Sodium hydroxide is0.1g, the reaction time is two hours and the reaction temperature is60℃; when making modification of anion on the one gram of dried sugarcane bagasse hemicelluloses, we can obtain more satisfactory anionic modified product under the conditions that the amount of Chloro-acetic acid is0.4g, the amount of Sodium hydroxide is0.3g, the reaction time is two hours and the reaction temperature is80℃;we can get better Gender modified products as the order of modification that first the Anion and then the cation. IR, NMR, scanning electronic microscopy and thermal analysis are used to do characterization on Gender modified bagasse hemicelluloses. The result shows that the amphoteric method was adopted in this study can draw the Carboxyl and Quaternary ammonium into sugarcane bagasse hemicelluloses, and found that the molecular structure and morphology of sugarcane bagasse hemicelluloses which were made amphoteric modification, its thermal stability decreased.4. Ions i.e. Cu2+, Pb2+and Cd2+were absorbed by the carboxylated bagasse hemicelluloses, and the effect of pH value to the adsorption capacity of metal ion has been studied. Results show that the optimal adsorption pH values for Cu, Pb and Cd were5.5,5.5and7.5, respectively. The adsorption capacity to ions Cu2+, Pb2+and Cd2+increased with increasing initial concentration of the metal ions, and the variations of adsorption capacity decreased in higher initial concentration of the metal ions. Thermodynamics analysis show that the adsorption of Cu2+, Pb2+and Cd2+fits the Freundlich isothermal adsorption model very well. It can be seen from the model that△H<0and△G<0, whichmeans that the absorption reaction was an exothermic reaction and the reaction was spontaneous. Kinetic study shows that absorption of the carboxylated bagasse hemicelluloses to ions Cu2+, Pb2+and Cd2+can be well described by the Pseudo second-order kinetics model. The theoretical values of the maximum absorption capacity qe,cal for ions Cu2+, Pb2+and Cd2+were20.28mg/g,82.64mg/g and30.58mg/g, respectively. In addition, at temperature of293K, the Pseudo second-order kinetics model for ions Cu2+, Pb2+and Cd2+were dqt/dt=0.0623(19.34-qt)2,dqt/dt=0.0237(59.52-qt)2and dqt/dt=0.0433(29.41-qt)2.5. Ions i.e. Cu2+, Pb2+and Cd2+were absorbed by the amphoteric bagasse hemicelluloses, and the effect of pH value to the adsorption capacity of metal ion has been studied as well.The results show that the optimal adsorption pH values for Cu2+, Pb2+and Cd2+are6.5,6.0and7.5, respectively. Net adsorption to ions Cu2+, Pb2+and Cd2+increased with increasing the initial concentration of the metal ions. Thermodynamics analysis show that the adsorption of Cu2+, Pb2+and Cd2+fits the Freundlich isothermal adsorption model quite well. It can be seen from the model that△H<0and△G<0, which means that the absorption reaction was an exothermic reaction and the reaction was spontaneous. Kinetic study shows that absorption of the amphoteric bagasse hemicelluloses to ions Cu2+, Pb2+and Cd2+can be well described by the Pseudo second-order kinetics model. The theoretical values of the maximum absorption capacity qe,cal for ions Cu2+, Pb2+and Cd2+were26.45mg/g,65.79mg/g and36.23mg/g, respectively. In addition, at temperature of293K, the Pseudo second-order kinetics model for ions Cu2+, Pb2+and Cd2+were dqt/dt=0.00936(26.45-qt)2,dqt/dt=0.0231(65.79-qt)2and dqt/dt=0.0428(36.23-qt)2.更多还原