煤矸石合成4A沸石及其对含氟废水的吸附研究

【作者】 王倩；

【导师】 卢新卫；

【作者基本信息】 陕西师范大学 ， 工程硕士（专业学位）， 2016， 硕士

【摘要】 4A沸石是人类合成的一种人工沸石,对环境不产生污染,离子交换性能和吸附性能较强。工业废物煤矸石的弃置不用和堆积都会对环境产生很大危害,而煤矸石中具有大量的Si02及A1203,可作为合成沸石的原材料。本课题利用煤矸石合成4A沸石,采用了分步溶出硅铝水热合成的方法,不需添加硅铝外源,方法简单容易控制,可操作性强,为煤矸石合成4A沸石的方法提供了一种新的途径。随着工业发展,工业含氟废水及部分生活饮用水严重超标,若处理不当,严重危害环境和人体健康。将合成的4A沸石用于处理含氟废水,探索其吸附性能和特征,不仅为处理含氟废水提供了一种廉价有效的吸附材料,而且达到了以废治废的环境目的。首先,本课题以煤矸石为原料,采用分步溶出硅铝水热合成法,探索了提取煤矸石中硅铝有效成分的影响因素以及晶化条件对合成产物的影响。结果表明：煤矸石经过热活化预处理后,其组分中的高岭石、石英等惰性成分转化为偏高岭石等活性成分；将热活化矸石与粉末状的碳酸钠按照质量比为1：1.3混合均匀在830℃的高温下熔融1h,通过表征发现煤矸石的硅铝成分充分转化为有利用价值的硅酸钠和硅铝酸钠；将熔融产物与水按固液比1：30混合,搅拌水溶1h,通过表征发现过滤后矿物中的硅酸钠几乎全部溶解在水中弃去,剩余产物主要为硅铝酸钠；将脱硅矸石与3mol/L的NaOH溶液混合,在60℃恒温下搅拌碱溶1h,硅铝酸钠几乎全部溶解,过滤得到硅铝溶液；将硅铝溶液经过陈化后进行晶化水热合成沸石,在较短的晶化时间下,合成产物为纯度较高的4A沸石,然而当晶化时间较长时则逐渐出现方钠石,本实验得到合成4A沸石的最佳晶化时间为4h,合成方钠石的最佳晶化时间为16h。然后,利用煤矸石合成的4A沸石作为吸附剂,探索其对模拟含氟废水的吸附性能和特征。结果表明：溶液的初始pH值对合成4A沸石的吸附除氟效果影响较大,合成沸石去除溶液中氟化物的适应pH范围是4-6；合成4A沸石的除氟吸附量随溶液与沸石的液固质量比的增加而增加,除氟率随液固比的增加而缓慢减小,当溶液与合成沸石的液固质量比为50：1时,既提高了沸石的单位吸附量,又保证了一定的除氟率；随着溶液初始浓度的增加,合成4A沸石对高浓度和低浓度的含氟溶液的吸附量均不断增长,合成4A沸石对高浓度含氟废水的除氟效果具有一定的浓度限定范围,而对于低氟废水的处理,合成4A沸石的吸附效果较好；振荡吸附时间对合成沸石的吸附除氟作用中,反应初期合成沸石对含氟废水吸附量的增加较快,而随着振荡时间的延长,合成沸石对溶液中氟的去除量增加缓慢,最后趋向于一个稳定的平衡状态。通过对合成沸石的吸附除氟结果进行动力学模型和等温吸附模型进行研究,发现合成4A沸石对废水的除氟过程较符合二级动力学模型和Freundlich等温吸附模型,表明该过程是以化学吸附和多分子层吸附作用为主。最后,用氯化铁和氢氧化钙溶液对合成4A沸石进行改性实验,探索其对高浓度的工业含氟废水的吸附性能。结果表明：氢氧化钙改性沸石的吸附除氟效果均高于氯化铁改性后的沸石,其中用氯化铁溶液改性沸石时,当Fe3+的质量分数和改性时间分别为0.05%和2h,对溶液中氟的去除效果最好；用氢氧化钙溶液改性沸石时,当Ca(OH)2的质量分数和改性时间分别为7%和2h,对溶液中氟的去除效果最好；氢氧化钙改性沸石对含氟溶液进行吸附后,溶液中的氟含量可达到我国工业废水排放的一级标准,而当溶液中氟离子的初始浓度为5OOmg/L时,吸附平衡后溶液中的氟含量可达到我国工业废水排放的二级标准；氯化铁改性沸石对初始浓度小于400mg/L的含氟溶液进行吸附后,溶液中的氟含量可达到我国工业废水排放的二级标准。更多还原

【Abstract】 4A zeolite, which doesn’t pollute the environment, is a kind of artificial synthesized zeolite with higher ion exchange performance and adsorption performance.The solid waste-Coal gangue will produce great harm to the environment because of discarding and accumulation. However, Coal gangue has a large number of SiO2 and Al2O3, which can be used as the raw material for the synthesized zeolite. This subject use coal gangue to synthesize zeolite 4A by adopting the stepwise method of dissolving silicon and aluminum in the hydrothermal synthesis, which needs no adding sources of silicon and aluminum. It provides a new way of easy method and high maneuverability for the synthesis of 4A zeolite from coal gangue. Along with industrial development, industrial fluoride wastewater and some of drinking water exceeded the standard, which will seriously be harm to the environment and human health if we not handled properly. Use the synthesized zeolite 4A to treat fluoride wastewater and explore its adsorption properties and characteristics can not only to provide an effective adsorption material for the treatment of fluoride wastewater, but also to achieve the environmental protection purpose.First, this subject explore the influencing factors of extracting effective silicon and aluminum components of coal gangueand the crystallization conditions influencing on the synthesized product. Results of the synthesis experiments are as follows.The group of kaolinite, quartz and other inert ingredients will transform into metakaolin and other active ingredients after overheating activation of coal gangue.The characterization of the coal gangue transforms into Na2SiO3and NaAlSiO4 after heatingthe activated gangue and Na2CO3 under a mass ratio of 1:1.3, high temperature of 830℃ and melting time of lh.Then, the molten product is mixed with water with the solid-liquid ratio of 1:30 and mixed time of 1h, and Na2SiO3 is almost completely dissolved in the water by characterization. Later, the desilication rock is mixed with 3mol/L NaOH solution with the temperature of 60℃ and time of 1h, and soNaAlSiO4is almost completely dissolved. Finally, put the aluminum silicon solution under aging and hydrothermal crystallization for synthesized zeolite. Zeolite 4A is generated with a short crystallization time, andsodalite needs longer crystallization time. The obtained crystallization time of zeolite 4Ais 4h and the synthesis of Sodalite is 16h.Then, explore the adsorption of fluorine to zeolite 4A synthesized from coal gangue. Results of the adsorption experiments are as follows. The initial pH of the solution has a great influence on the defluorinating efficiency to the synthetic zeolite, and the optimal pH range is 4-6. With the increase of the mass ratio of solution to zeolite, the quantity of fluorine adsorption increases, while the defluorinating rate decrease slowly. It can not only improve the quantity of fluorine adsorption, but can guarantee a greater defluorinating rate when the ratio of solution to zeolite is 50:1. The unit fluorine adsorption is increasing to varying degrees with the increase of initial concentration. The adsorption of fluorine to the synthetic zeolite has a certain concentration limit range for the higher concentration fluoride, while the adsorption effect is better to the lower fluoride concentration. The fluorine adsorption increases faster during the early reaction, while the removal amount increases slowly with the longer adsorption time, and finally it tends to a stable equilibrium. And the fluoride removal process complied with the pseudo-second-order model and the Fleundlich isothermal adsorption model, indicating that the adsorption process is a chemical and multilayer adsorption.Finally, explore the adsorption of fluorine to zeolites modified by ferric chloride and calcium hydroxide solution. The optimum conditions of zeolite modified by ferric chloride are the Fe3+mass fraction of 0.05% and modification time of 2h, and optimum conditions by calcium hydroxide are the Ca(OH)2 mass fraction of 7% and modification time of 2h. The defluorinating effect of zeolite modified by calcium hydroxide is higher than the ferric chloride. The fluorine content can reach the primary standard of industrial waste water discharge in our country after using the zeolite modified by calcium hydroxide, and when the initial concentration of fluorine is 500mg/L, it can reach the secondary standard of industrial waste water discharge. When the initial concentration of fluorine is less than 400mg/L, the content of fluorine can only reach the secondary standard after using the zeolite modified by ferric chloride.更多还原