矸石基NaX型沸石对水中重金属离子的吸附性能研究

发布时间：2018-05-03 18:28

本文选题：矸石基NaX型沸石 + 重金属　；参考：《陕西师范大学》2015年硕士论文

【摘要】：煤矸石是煤炭开采、洗选过程排放的固体废物,其大量堆积会对生态环境产生危害,因Al2O3和SiO2为其主要化学成分,可作为合成沸石分子筛原料。本文以陕西省白水煤矿的煤矸石为原料,制备出表面形貌完整的NaX型沸石分子筛。将所制备的NaX型沸石用作吸附剂,探讨了其对Cd2+、Cr3+Cu2+三种重金属离子在单元系统、双元系统、三元系统中的吸附过程。因六价铬的毒性比三价铬大很多,所以本文探讨了矸石基沸石及其改性沸石对Cr(Ⅵ)的吸附性能。共研究了三种不同试剂对矸石基NaX型沸石的改性方法及改性后沸石的吸附条件和机制,并用扫描电镜对沸石改性前后的形貌进行了表征。每个吸附过程都与等温吸附模型和吸附动力学模型进行拟合。通过上述研究工作得出结论如下：(1)煤矸石经破碎-粉磨-酸浸-洗涤-干燥-碱熔-陈化-晶化等过程合成出了表面形貌完整的NaX型沸石分子筛。其中碱熔配比为煤矸石：NaOH=1:1.2,碱熔温度为650℃陈化时间为6 h,晶化温度为110℃,时间为12 h。(2)矸石基NaX型沸石对Cd2+、Cu2+和Cr3+的吸附单因素影响实验中,最佳初始pH值为4,沸石添加量为0.15 g,随着初始浓度的增加,沸石对三种重金属离子的单位吸附量均有不同程度的增加,而去除率则逐渐减少。沸石对Cr3+的吸附无论在单元系统还是多元系统,都60 min后达到吸附平衡。而沸石对Cd2+和Cu2+的吸附在单元系统和无Cr3+参加的系统中都能在5～10分钟后达到吸附平衡,有Cr3+参加的系统中则是60 min后达到吸附平衡。(3)表征结果显示,经氯化铝和十六烷基三甲基溴化铵(HDTMA)改性的矸石基沸石的晶型并没有发生大的变化,改性后沸石的体积都比改性前略有扩大,且表面都附着了改性剂。经硫酸亚铁改性的矸石基沸石其晶型被破坏。(4)改性前矸石基NaX型沸石对Cr(Ⅵ)的吸附效果在pH为8时最佳,但吸附率并不高。(5)不同改性剂的最佳改性条件分别为：硫酸亚铁改性沸石的最佳改性浓度为0.3 mol/L,改性时间为2h；氯化铝改性沸石的最佳改性浓度为20%,最佳改性时间为4 h；十六烷基三甲基溴化铵(HDTMA)改性沸石的最佳改性浓度为0.5%,最佳改性时间为2 h。(6)通过探讨不同改性沸石吸附过程的影响因素,得到：三种改性沸石中,硫酸亚铁改性沸石的最佳吸附初始pH值为4,氯化铝改性沸石和十六烷基三甲基溴化铵(HDTMA)改性沸石的最佳吸附初始pH值为2。三种改性沸石对Cr(Ⅵ)的去除率随初始浓度的升高而降低；其单位吸附量则随初始浓度升高而增加。同等初始浓度和体积下,在实际应用中改性沸石的用量需大于0.25 g方能达到无害效果。经实验验证,三种改性沸石均能在120 min达到吸附平衡。(7)通过模型拟合发现,所有的单元系统吸附过程都符合Langmuir等温吸附模型和伪二级动力学吸附模型,多元系统中矸石基NaX型沸石对三种重金属离子的等温吸附更符合扩展的Langmuir模型。(8)通过比较不同的吸附剂在各自最佳pH值以及相同的其他吸附条件下对Cr(Ⅵ)的吸附效果得出,经不同方法改性后,矸石基NaX型沸石对Cr(Ⅵ)的吸附效果均有不同程度提高,其中有机改性沸石的去除效果最好。
[Abstract]:Coal gangue is a solid waste discharged from coal mining and washing process. A lot of accumulation will be harmful to the ecological environment. Because Al2O3 and SiO2 are the main chemical components, it can be used as the raw material of synthetic zeolite molecular sieves. In this paper, the NaX zeolite molecular sieves with complete surface morphology are prepared from the coal gangue of Shaanxi Baishui coal mine. NaX zeolite is used as an adsorbent. The adsorption process of three heavy metal ions of Cd2+ and Cr3+Cu2+ in unit system, dual system and three element system is discussed. The toxicity of six valence chromium is much larger than that of trivalent chromium. Therefore, the adsorption properties of gangue based zeolite and its modified zeolite to Cr (VI) are discussed in this paper. A total of three different reagents have been studied. The modified method of stone based NaX zeolite and the adsorption conditions and mechanism of the modified zeolite were characterized by scanning electron microscope. Each adsorption process was fitted with the isothermal adsorption model and adsorption kinetic model. Through the above research work, the conclusion was drawn as follows: (1) the coal gangue was broken through grinding and acid leaching. NaX zeolite molecular sieves with complete surface morphology were synthesized by washing - drying - alkali melting - aging and crystallization. The ratio of alkali fusion was NaOH=1:1.2, alkali melting temperature was 6 h at 650 C, crystallization temperature was 110, and 12 h. (2) NaX zeolite of Gangue Based on Cd2+, Cu2+ and Cr3+ The initial pH value is 4 and the zeolite addition is 0.15 g. With the increase of initial concentration, the unit adsorption capacity of the three heavy metal ions is increased in varying degrees, while the removal rate decreases gradually. The adsorption equilibrium of zeolite to Cr3+ is reached after 60 min in the unit system or in the multiple system. The adsorption of zeolite to Cd2+ and Cu2+ is the absorption of zeolite. The adsorption equilibrium can be reached in the unit system and the system without Cr3+ participation in 5~10 minutes. The adsorption equilibrium is reached after 60 min in the system with the participation of Cr3+. (3) the characterization results show that the crystalline form of the Gangue Base boiling stone modified by aluminum chloride and sixteen alkyl three methyl ammonium bromide (HDTMA) has not changed greatly, and the modified zeolite has been modified. The volume of the Modified Gangue based zeolite modified by ferrous sulfate was destroyed. (4) the adsorption of Cr (VI) on the Modified Gangue Based NaX zeolite was best at the time of pH 8, but the adsorption rate was not high. (5) the optimum modification conditions of different modifiers were the modified boiling of ferrous sulfate. The best modified concentration of the stone was 0.3 mol/L and the modified time was 2h, the optimum modified concentration of aluminum chloride modified zeolite was 20%, the optimum modification time was 4 h, the optimum modified concentration of sixteen alkyl three methyl ammonium bromide (HDTMA) modified zeolite was 0.5%, the optimum modification time was 2 h. (6), and the influence factors of the adsorption process of different modified zeolite were discussed. The optimum adsorption initial pH value of the three modified zeolite was 4, the optimum adsorption initial pH value of aluminum chloride modified zeolite and sixteen alkyl three methyl ammonium bromide (HDTMA) modified zeolite was 2. three kinds of modified zeolite, and the removal rate of Cr (VI) decreased with the increase of initial concentration; and its unit adsorption amount followed the initial concentration. In the same initial concentration and volume, the dosage of modified zeolite needed to be more than 0.25 g can achieve harmless effect under the same initial concentration and volume. The three modified zeolites can achieve the adsorption equilibrium at 120 min. (7) the adsorption process of all the unit series is in accordance with the Langmuir isothermal adsorption model and the model fitting. The pseudo two stage kinetic adsorption model, the isothermal adsorption of three heavy metal ions by the Gangue Based NaX zeolite in the multicomponent system is more consistent with the extended Langmuir model. (8) by comparing the adsorption effects of different adsorbents on the Cr (VI) under the best pH values and the same other adsorption conditions, after the modification of different methods, the gangue base NaX The adsorption effect of zeolite on Cr (VI) has been improved to varying degrees, among which organic modified zeolite has the best removal effect.

【学位授予单位】：陕西师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703;X752

【参考文献】