【作者】 刘栋宏；

【导师】 郑红；

【作者基本信息】 中国地质大学（北京） ， 应用化学， 2010， 硕士

【摘要】 氟是人体必须的微量元素之一,适量的氟摄入可促进人体牙齿与骨骼发育,但超过一定范围将对人体健康造成严重危害。饮用水是人体摄入氟的主要来源,近期关于北京市海淀区农村饮用水水质调查研究表明,海淀区许多农村地区地下水氟含量明显超标,这严重威胁了当地居民的身体健康。沸石与层状双金属氢氧化物具有优异的吸附性能,本课题的研究目的是利用辽西南地区储量丰富、成本低廉的天然沸石,通过负载双金属氢氧化物来提高其吸附量,开发出高效的除氟材料。天然沸石经过XRD、化学分析与电子探针分析,表明其主要物相为斜发沸石与石英,含量分别为83.18%与7.26%。负载层状双金属氢氧化物后经过XRD与SEM分析,发现XRD结果中可看出明显的层状双金氢氧化物的峰,SEM图片中可看出沸石表面有白色物质。动力学吸附实验的优化条件为:pH4～6,用量5g/L,平衡时间8h,振荡速度180r/min。动力学研究表明:吸附反应动力学符合准二级反应模型,其模型计算吸附量q_e(cal)与实验吸附量q_e(exp)相近,其相关系数R~2都大于0.99;内扩散模型计算结果推测吸附反应过程分两个阶段,第一个阶段为材料表面吸附,第二个阶段吸附由材料表面进入内孔,且第一阶段的吸附速率比第二阶段快。吸附等温线的曲线形状为S型,langmuir模型不适合解释本实验的等温线,Freundlich模型表明在氟浓度低时吸附不利,氟浓度高时吸附有利。D-R模型计算结果表明,在氟浓度较低时,吸附主要为物理吸附;在氟浓度较高时,吸附主要为化学吸附。除氟机理分析表明除氟过程为离子交换过程,起主要除氟作用的物质为层状双金属氢氧化物。与其他沸石负载方法(负载铝与负载锆)相比,负载层状双金属氢氧化物除氟更具优势,吸附量比原矿天然沸石吸附量增大14倍左右,在去除高浓度氟方面具有良好的实际应用前景。更多还原

【Abstract】 Fluorine is a trace element necessary for human body,appropriate amount of fluoride intake may promote the development of human teeth and bones,but beyond a certain range will cause harm to human health.Drinking water is the main source of fluoride consumption for human.The recently research on the drinking water quality in rural areas of Haidian District shows that the fluoride content of groundwater significantly exceed,which is a serious threat to the health of local residents.Zeolite and layered double hydroxides(LDHs) have excellent adsorptive performance,the purpose of this paper is to develop an efficient fluoride removal materials using low-cost natural zeolite of southwest Liaoning,Zn-A1 layered double hydroxides will be loaded on the surface of zeolite to improve its adsorption capacity.The X-ray diffraction,chemical analysis and electron microprobe analysis results indicate the main phases of natural zeolite are clinoptilolite and quartz.After loaded Zn-Al layered double hydroxides,the Zn-Al LDHs peaks can be found,and some white substance can be seen at the surface of zeolite through the scanning electron micrograph.For kinetics study,the experiments demonstrate that maximum fluoride removal was obtained at a pH between 4 and 6,and it took 8h to attain equilibrium,the optimized amount is 5g/L and the speed of oscillation is 180 r/min.Kinetics adsorption profiles offered excellent fit with pseudo-second-order model with a high R~2 value over 0.99.The intraparticle diffusion model indicates there are two-stage adsorption processes,in the first stage,the fluoride adsorption occurs at the surface,in the second stage the adsorption goes into the hole,the adsorption rate of the second stage is faster than the first stage.The shape of adsorption isotherm curve is S, Langrnuir model is not suitable to explain the experimental isotherm,Freundlich model demonstrate that the adsorption is unfavorable in the low fluoride concentration and is favorable in the high concentration.The calculated results of D-R model indicate that when the fluoride concentration is low,the adsorption is mainly physical;when the fluoride concentration is high,the adsorption is mainly chemical. The mechanism of fluoride removal for this material is ion exchange,the double hydroxide play a major role in the removal of fluoride.Compared with other methods(aluminum and ziconium),zeolite supported layered double hydroxide is better,the amount of adsorption is 14 times than natural zeolite,it has a good prospect for practical application on the removal of high fluoride concentration.更多还原