【作者】 张婧；

【导师】 谢绍东； 何玉山；

【作者基本信息】 北京大学 ， 环境科学， 2008， 硕士

【摘要】 水体铅和氟污染会对水生生物以及人体造成严重危害,研究经济高效的含铅废水和高氟水的处理方法具有重要意义。吸附法具有操作简便、处理效果好等优点,在水处理中一直是研究的焦点,近年来集中于寻找低成本吸附剂以代替广泛应用的活性炭。凹凸棒石粘土系天然矿物原料,在我国主要产于苏皖一带,来源广泛,价格低廉,具有较强的吸附能力。本研究以江苏盱眙产凹凸棒原土和经过镁铝盐改性后的凹凸棒土为吸附剂,在表征其物理化学性质和形貌结构的基础上,研究其处理含铅废水和高氟水的吸附热力学和吸附机理。应用Excel规划求解和非线性拟合方法探寻吸附体系的等温线,结果发现,凹凸棒土吸附Pb²⁺和F^-的吸附过程均遵循Langmuir和Redlich-Peterson方程,而不符合Freundlich等温线;吉布斯自由能、焓变和熵变的数据表明,其体系均为自发性的吸热反应;静态实验表明,温度为313K时,凹凸棒土吸附铅离子的理论q_m为114.0mg/g;改性凹凸棒土吸附氟离子的理论q_m为44.0mg/g。根据Langmuir单层吸附理论,计算出Pb²⁺在凹凸棒土上的覆盖面积为17-19m²/g。通过分析XPS材料表面测试结果和吸附前后溶液pH值的测试结果,初步推测凹凸棒原土吸附铅离子是基于静电吸附和与吸附剂表面的OH^-作用而沉积;改性质量比为attapulgite:MgCl₂·6H₂O:AlCl₃·2H₂O=2:1:2的凹凸棒土对氟离子吸附容量最大,主要是通过离子交换而被吸附。天然凹凸棒土和改性凹凸棒土对铅离子和氟离子具有很好的吸附效果,是合适的吸附剂,具有广泛的工程应用前景。更多还原

【Abstract】 Since high lead and fluoride concentrations in water cause great damage to aquatic animals, plants and human body, it is essential that there are technologies for controlling the concentrations of lead and fluoride in aqueous emissions. One effective and economic approach is to use alternative adsorbents. Extensive investigations have been carried out to identify suitable adsorbents in recent years. For its low costs and great performance in the adsorption of many pollutants, attapulgite has been obtaining increasing scientific attention.The attapulgite used in this study is from Xuyi in Jiangsu province. Adsorption of lead ions by natural attapulgite and fluoride ions by three modified attapulgites with magnesium and aluminum salts are conducted by batch experiments. Based on the physical and chemistry properties of the attapulgite, the thermodynamics and mechanism of the adsorption processes have been mainly studied.With the software Microsoft Excel, two-parameter Langmuir and three-parameter Redlich-Peterson isotherms are examined as the best-fitting models for the experimental data by the non-linear method. An increase in temperature results in a higher lead or fluoride loading per unit weight of the adsorbent, suggesting that both the two adsorption processes are spontaneous and endothermic. Besides, the two are both favorable adsorption systems. The maximum adsorption capacities for attapulgite/lead and modified attapulgite/fluoride adsorption system are 114.0mg/g and 44.0mg/g in the temperature 313K respectively. According to the monolayer adsorption theory of the Langmuir isotherm, the specific surface area of attapulgite towards Pb²⁺ binding is 17-19m²/g.The XPS test for the surface of the attapulgite and changes of the pH value in the aqueous solutions before and after the reaction prove that there exist electrostatic gravitations in the attapulgite/ lead system but also precipitation of the lead（II）. Modified attapulgite with a mass ratio attapulgite:MgCl₂·6H₂O:AlCl₃·2H₂O = 2:1:2 has higher adsorption efficiency for fluoride ions. The agreement of the adsorption capacities and changes of the hydroxy ion concentration indicates that anion exchange reactions occurr in the adsorption process.The experimental results suggest that nature attapulgite is a suitable adsorbent for removing lead ions and the modified attapulgite suitable for fluoride ions, which can be widely applied in the water treatment projects.更多还原