【作者】 徐丹；

【导师】 张兴旺；

【作者基本信息】 浙江大学 ， 应用化学， 2014， 硕士

【摘要】 疏水性有机污染物(HOCs)广泛存在于废水中,多数具有致癌、致畸、致突变效应,会对人类健康和生态环境造成永久性危害。由于HOCs的低水溶性高亲脂性,常规的物化方法对其处理效果通常较差,其生物可降解性低且具有毒害,会导致废水生化处理工艺难以稳定运行和达标排放,而吸附法虽有良好的去除效果,但其选择性差且再生困难,难以实现大规模应用。温敏水凝胶由于其独特的温度敏感性,具有再生容易和选择性吸附等特点,如果骨架中引入疏水基团其会呈现疏水性,对HOCs能有效吸附。本文采用丙烯酸丁酯(BA)作为疏水单体,与N-异丙基丙烯酰胺(NIPAM)共聚制得疏水改性温敏水凝胶,并以五氯苯酚为疏水有机目标污染物,研究了疏水改性温敏水凝胶对疏水性有机物的吸附行为和作用机理。将BA引入NIPAM水凝胶骨架,得到PNIPAM-BA疏水改性温敏水凝胶。采用SEM、DSC热分析、接触角测试等手段进行理化表征。结果表明,BA的引入增加了温敏水凝胶的疏水性,其最低临界溶解温度(LCST)在30℃左右,当温度小于LCST时吸水溶胀,当大于LCST时失水收缩,利用其温敏效应可实现目标污染物的选择性吸附和吸附剂的再生利用。对疏水改性温敏水凝胶吸附五氯苯酚进行了研究,结果表明疏水基团的引入提高了其对五氯苯酚的去除效率。去除率最高的是BA含量为11%的PNIPAM-BA疏水改性温敏水凝胶,该材料对五氯苯酚的去除率最高可达到95%,为传统温敏水凝胶的1.36倍。疏水改性温敏水凝胶对五氯苯酚的吸附符合拟二级动力学和Langmuir等温吸附模型。吸附热力学研究表明其对五氯苯酚的吸附是一个自发放热的过程。溶液的pH值和温度对吸附有很大影响,在pH=3条件下吸附最佳,随温度的增加吸附量明显下降。吸附机理包括疏水分配作用与表面非线性分配共同作用,在低浓度时以疏水分配作用为主,疏水性表面在整个过程中发挥着极其重要的作用。疏水改性温敏水凝胶对疏水性有机污染物具有选择吸附特性。在多元溶质体系中,苯酚及2,4-二氯苯酚的存在对疏水改性温敏水凝胶吸附五氯苯酚存在一定的促进作用,萘、三氯苯和五氯苯酚的共存有利于提高相互之间的吸附性能,产生协同吸附效应。疏水改性温敏水凝胶具有稳定的再生性能,在50℃下脱附即可实现完全再生,脱附率达到100%。经多次循环再生后,仍能维持良好的吸附稳定性,实现了吸附剂简单经济的再生循环利用。更多还原

【Abstract】 Hydrophobic organic contaminants (HOCs) are widely present in the waste water, and they will cause permanent harm to human health and the environment. Because of the low water solubility and high lipophilicity of HOCs, the physicochemical treatments for the removal of HOCs are poor, and the biochemical processes are also difficult to operate due to the low biodegradability and toxicity. Although the adsorption removal is effective, it is difficult for massive applications owing to the poor selectivity and difficult regeneration. Due to the unique temperature-sensitive, thermo-sensitive hydrogels have characteristics of easy regeneration and selective adsorption, and the introduction of hydrophobic groups will enhance the adsorption of HOCs). In this work, a hydrophobic monomer butyl acrylate (BA) and N-isopropyl acrylamide (NIPAM) were synthesized to obtain hydrophobically modified thermo-sensitive hydrogels. Moreover, their adsorption performance for the removal of HOCs were evaluated.The physicochemical properties of thermo-sensitive hydrogels were characterized by SEM, DSC analysis, contact angle measurements. The results showed that the introduction of butyl acrylate enhanced the hydrophobicity of the thermo-sensitive hydrogels. The lower critical solution temperature(LCST) of the hydrophobic modified thermo-sensitive hydrogels was about30℃, and below LCST the hydrogels will be swollen, while above the LCST, the hydrogels will shrink. Due to the temperature-sensitive effects, they can be used for the adsorption of target pollutants and are easy for regeneration.Pentachlorophenol (PCP) was used as HOCs for the research of the adsorption performance of hydrophobic modified thermo-sensitive hydrogels. The results demonstrated that the adsorbed amounts of PCP were significantly increased due to the introduction of hydrophobic groups. Among them, the best sample is PNIPAM-11%BA, its removal rate of PCP was95%, which was1.36times of that by traditional thermo-sensitive hydrogel. The adsorption process followed the pseudo-second-order kinetic and Langmuir model. Adsorption thermodynamics showed that the adsorption process is an exothermic process with spontaneous nature. The solution pH and temperature have a great influence on the adsorption process, the adsorption capacity reached maximum when pH=3, and the adsorption capacity decreased with temperature increasing. The distribution function and surface adsorption existed for the adsorption process of hydrophobic modified thermo-sensitive hydrogels, where distribution function was dominated at low concentration and the hydrophobic surface play an extremely important role in the whole process.The adsorption of HOCs by hydrophobic modified thermo-sensitive hydrogels had selective properties. In the multi-solute system, the presence of phenol and2,4-dichlorophenol encouraged the adsorption capacity of PCP by hydrophobic modified thermo-sensitive hydrogels, and the coexistence of naphthalene, trichlorobenzene and pentachlorophenol helped to improve the adsorption performance.The cyclic PCP adsorption/desorption experiments of hydrophobic modified thermo-sensitive hydrogels showed that the adsorbed PCP could be completely desorbed at50℃, where the desorption rate was100%. The adsorption capacities of hydrophobic modified thermo-sensitive hydrogels were stable after10cycles of adsorption and regeneration cycles. These results suggest that the hydrophobic modified thermo-sensitive hydrogel would be a simple, high-efficiency and easy-regeneration adsorbent for the removal of hydrophobic organic contaminant in waste water.更多还原