【作者】 许丽娟；

【导师】 庞秀言；

【作者基本信息】 河北大学 ， 应用化学， 2011， 硕士

【摘要】 膨胀石墨是一种可再生环境修复材料。它是以天然鳞片石墨为原料,利用电化学氧化或化学氧化的方法使某些原子或原子团插入石墨层间,得到的一种石墨层间化合物(可膨胀石墨),可膨胀石墨经过瞬时高温处理后发生膨胀,形成的一种具有丰富的孔隙结构、低堆积密度、高化学稳定性的物质。本文以硫酸作为插层剂,高锰酸钾为氧化剂制备膨胀石墨,并利用X-ray衍射图谱、能量色散谱、比表面积、孔径、孔容积等对原料石墨、可膨胀石墨、膨胀石墨等进行了表征。研究了膨胀石墨对聚乙烯醇的吸附性能以及对二甲酚橙和蒽醌-1-磺酸钠的竞争吸附性能。聚乙烯醇(PVA)是由聚醋酸乙烯醇解而得到的,性能介于橡胶和塑料之间。由于PVA具有良好的黏附性、浆膜强韧性和耐磨性,在纺织工业中得到广泛应用,但其非环保性也成为长期困扰印染废水处理的难题。由PVA构成的有机污染物浓度高且难被生物降解(B/C小于0. 1)。含PVA的印染废水排入水体后,PVA会在水环境中大量积累,使水体表面泡沫增多,黏度加大,影响好氧微生物的活动,从而造成严重的环境问题。本文以膨胀石墨为吸附剂,系统地考察了膨胀石墨对聚乙烯醇(500),聚乙烯醇(700),聚乙烯醇(1750)吸附热力学及动力学规律。动力学研究表明膨胀石墨对聚乙烯醇的吸附过程可以用二级模型来表示,且吸附过程为内扩散控制。热力学研究表明膨胀石墨对聚乙烯醇的吸附等温线为I型,吸附过程是自发进行的,吸附性能不仅与聚乙烯醇浓度、吸附时间、溶液离子强度等因素有关,而且与聚乙烯醇的自身分子量有关。聚乙烯醇以平躺方式吸附于膨胀石墨表面,吸附等温线可以用Langmuir方程来表征。用蒽醌-1-磺酸钠和二甲酚橙染料作为分子量有差异的两种有机吸附质,本文研究了它们在不同膨胀容积的膨胀石墨上的吸附及竞争吸附特性。研究表明:膨胀石墨对二甲酚橙和蒽醌-1-磺酸钠都有一定吸附能力,在单组分吸附中,二甲酚橙在膨胀石墨上的吸附等温线为II型,而蒽醌-1-磺酸钠的吸附等温线为I型;在两组分共存竞争吸附中,第二种吸附质的存在会显著降低第一种吸附质在膨胀石墨上的吸附量,但竞争吸附质的存在不影响第一种吸附质的吸附等温线类型,与单组份时相同,二甲酚橙和蒽醌-1-磺酸钠在膨胀石墨相同结构位点上存在竞争吸附;吸附过程是自发进行的,增大溶液的离子强度和膨胀容积使膨胀石墨对二甲酚橙和蒽醌-1-磺酸钠的吸附量升高,但吸附剂膨胀容积不影响其吸附等温类型;二甲酚橙和蒽醌-1-磺酸钠单组分体系、双组分体系在膨胀石墨表面上的吸附过程均可以用准二级模型来描述,吸附速率常数随吸附过程温度的升高略有增加,但影响不大,吸附作用以物理吸附为主。更多还原

【Abstract】 Expanded graphite (EG) is a renewable environment rehabilitation material. The graphite intercalation compound with some atomes and radicles is prepared through electrochemical oxidation methods or chemical oxidation methods using natural graphite falakes as raw materials. EG is obtained through the instant expand of the graphite intercalation compound. EG have many special characteristics, such as porous structure, low density and high chemical stability.In this paper, graphite intercalation compound is prepared with H2SO4 as inserting reagent and KMnO4 as oxidizing agent. EG is obtained through the instant expansion of the graphite intercalation compound under 900℃. The composition, structure and properties of the graphite intercalation compound are characterized and analyzed with XRD, EDS. Specific surface area, pore diameter and pore volume of EG are also detected. Adsorption capacities of EG for Polyvinyl Alcohol (PVA) and competitive adsorption for Sodium anthraquinone-1-sulfonate (SAS) and xylenol orange (XO) are investigated.PVA is obtained by alcoholysis of polyvinyl acetate, and its performance is between rubber and plastic. PVA has been widely used in the textile industry because it’s good adhesion, film toughness and wear resistance, but it also has the non-environment friendly problems. PVA waste water has the characteristics of high organic pollutant concentration and difficult to be biodegradable (B/C is less than 0.1). After discharging into the water body, PVA will accumulate in water body, so that it makes the water surface foam and viscosity increase, and also affect the activities of aerobic microorganisms. So it can result in serious environmental problems. In the present study, EG is used as an adsorbent, and its adsorption capacity for PVA with different polymerization degrees (DP) of 500, 700, 1750, is studied. We investigate the adsorption kinetic and thermodynamic characteristics of EG for PVAs in aqueous solution.Kinetic studies show that the kinetic data can be delineated by pseudo second-order kinetic model, and internal diffusion may dominate the overall adsorption kinetics. The thermodynamic studies show that the adsorption of PVA on EG is spontaneous and the adsorption isotherm on EG is type I. Adsorption capacities are not only dependent on initial concentration of PVA, adsorption time and ionic strength, but also relate with the polymerization degree of PVA. The adsorption characteristics can be described with Langmuir isotherms equation, and the adsorbed PVA molecules lie flat on the surface of EG.In the research, two compounds of Sodium anthraquinone-1-sulfonate (SAS) and xylenol orange (XO) with obvious difference in molecular weights were selected as organic adsorbates. The adsorption and competitive adsorption characteristics on EG were studies. The results are: EG has adsorption capacity for both SAS and XO. In the adsorption of single component system, the isotherm of SAS on EG is type I; while, isotherm of XO is type II. In the competitive adsorption of dual component system, the existence of the other component SAS or XO would greatly decrease the adsorbance of EG for XO or SAS, which might be caused by the competitive adsorption of SAS and XO for the same adsorbing site on EG. But the existence of competitive adsorbates doesn’t affect the adsorption isotherm, it is the same as the one-component system. Adsorption of SAS or XO on EG is spontaneous, and the increase of ionic strength, temperature and expansion volume of adsorbates would cause the increase of SAS or XO adsorbance, but expansion volume does not affect adsorption isotherm type. No matter the adsorption of single component system of SAS or XO, or the competitive adsorption of dual component system of SAS and XO, the adsorption kinetics models can all be well described with pseudo second-order kinetic model. Adsorption rate increases with the increase in temperature. Physical adsorption is the main action between EG with SAS or EG with XO.更多还原