论文标题:天然改性除氟吸附剂的制备与机理
Advanced Purification and Treatment of the Micro-Polluted Raw Water
论文作者 雅非群
论文导师 马伟,论文学位 硕士,论文专业 无机化学
论文单位 大连理工大学,点击次数 165,论文页数 70页File Size3207k
2004-06-01论文网 http://www.lw23.com/lunwen_1629767/ 生物质,氟,壳聚糖,生物吸附,改性,磁性
biomass, fluoride, chitosan, biosorption, modification, magnetic
生物质来源广泛，有良好的吸附性能和高度的选择性。本文针对饮用水中的氟离子，以生物质材料壳聚糖为原料进行专题研究。壳聚糖属天然高分子化合物，其分子链上的游离氨基在弱酸溶液中结合一个质子生成阳离子聚合体，有很强的吸附能力。通过优化化学改性条件包括化学浸，甲醛接枝与浸铁，高温煅烧，高分子聚合和磁性高分子聚合，首次成功的制备了具有磁响应功能和生物可降解性的复合微球，达到了高效除氟的目的。此外，还与天然材料改性得到的骨碳吸附剂及天然矿物电气石和常规除氟剂活性氧化铝进行对比，结合数学模型及一系列红外光谱，电镜能谱分析等实验检测手段，对改性吸附剂的作用机理进行了研究。 实验结果表明： 1．生物质原料改性得到的吸附剂具有较好的吸附效果。当pH为7，平衡浓度为120mg／L和78mg／L时，磁性吸附剂和骨碳改性吸附剂的吸附量分别为17.68mg／g和18.11mg／g，均好于传统的除氟剂活性氧化铝。 2．磁性吸附剂的静态吸附过程以单分子层吸附为主。而骨碳吸附剂，电气石和活性氧化铝以多分子层吸附为主。吸附剂磁性的大小对它的除氟能力有一定的影响，当饱和磁化率由56.67μW_b·m·kg~(-1)减小为48.83μW_b·m·kg~(-1)时，吸附剂的吸附量由4.24mg／g下降为3.98mg／g。 3．磁性吸附剂在不同吸附时间吸附能力的变化曲线接近二级动力学反应机理，而在柱状实验中，原水流经一定高度的吸附床时，磁性吸附剂和骨碳吸附剂的吸附过程满足一级动力学方程。 4．改性后的磁性吸附剂在原有-NH_2等基团的基础上引入了Ca~(2+)，Fe~(3+)等离子，大大加强了该吸附剂的吸附性能。粒子内部磁性的存在，产生了某种类聚效应，使其内部磁场变得有规则，从而加强了吸附性能。在碱性条件下，粒子之间的作用力更强，吸附剂的吸附容量也更大。 5．反洗实验结果表明，经二次反洗后，磁性吸附剂和骨碳吸附剂的吸附量仍可以达到原来的98％和98.5％。因此，具有良好的实际应用价值。 从上述实验结果可以看出，赋磁改性处理后的壳聚糖吸附剂以及骨碳改性得到的吸附剂具有良好的吸附性能。与常规除氟方法相比，操作条件简单，除氟效率高。因此，天然材料改性后的吸附剂适用于去除水中的氟离子，符合环境材料的要求，具有实际应用价值。
As natural macromolecule, chitosan has excellent bioactivity and selectivity. This study investigated the feasibility of its modified materials for fluoride removal from drinking water and magnetic chitosan beads were prepared with high uptake capacity for the first time. Candidates of other natural macromolecules that modified bone char, tourmaline and established methods were also compared. Experimental results showed that both of magnetic adsorbent and bone char had better adsorbing ability than activated alumina. At pH 7 and the equilibrium concentrations were 78mg/L and 120mg/L respectively, the uptake capacity of the magnetic chitosan and bone char were 17.68mg/g and 18.11mg/g. Batch and Column experiments were also conducted to describe the adsorbing process. Empirical models and instrumental analysis showed that the adsorption of the magnetic adsorbent to fluoride is a chemical process. The environmental scanning electron microscope indicated Fe3+, Ca2+ ions were included after modification. So the adsorbing process was enhanced by the magnetic field, which was produced by the magnetic particles themselves. Particles with higher ratio saturated magnetizing strength or fewer diameters had higher uptake capacity. Furthermore, through second regeneration, the efficiency of the magnetic adsorbent and bone char could also attain 98% and 98.5%. The results indicated that the composite adsorbents, which were the modified adsorbents of natural materials, satisfied the fundamental requests of environmental materials, and bone char had gotten successfully application in the practice.
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