工业粉煤灰制备硅材料及其吸附水中六价铬的研究

发布时间：2018-01-03 06:35

本文关键词：工业粉煤灰制备硅材料及其吸附水中六价铬的研究　出处：《昆明理工大学》2015年硕士论文　论文类型：学位论文

更多相关文章： 粉煤灰 硅材料 六价铬 吸附机理

【摘要】：六价铬(Cr(Ⅵ))是高度毒性的重金属污染物,具有致畸、致癌和致突变作用,是美国EPA列为水体一级优先控制污染物,也是我国列为"十二五"规划中的重点防控的重金属污染物。我国是有色金属生产第一大国,工业生产过程中排放大量的含Cr(Ⅵ)废水废渣,水体的铬污染严重影响居民饮用水安全和工业生产用水,加之我国面临严重的水资源短缺问题,水体Cr(Ⅵ)污染的防治是工业废水治理的重中之重。吸附法处理重金属废水效果明显,操作简便,原料来源广泛且可循环利用,因而广泛运用于处理Cr(Ⅵ)废水。吸附法的技术关键在于吸附剂的选择。本课题采用不同硅源、不同模板剂、不同的老化和改性方法制备了硅材料SBA-15和MCM-41,并将其作为吸附剂,通过静态实验吸附水中的Cr(Ⅵ),通过比较吸附效果筛选出最优吸附剂。实验结果发现,以工业粉煤灰为硅源、十六烷基三甲基溴化铵(CTAB)为模板剂,通过碱熔融-微波老化合成法制备的硅材料MCM-41(命名为FMC)对Cr(Ⅵ)的吸附效果最佳。对粉煤灰制备的介孔硅材料MCM-41进行XRD和N2吸附-脱附表征,表征结果说明该材料具有介孔结构的特征,但有序度差,比表面积小,原因是粉煤灰中杂质较多,在制备过程中影响了材料的孔隙形成和分布。考察筛选出的最优吸附剂FMC对Cr(Ⅵ)的吸附性能,考察内容包括溶液初始pH值、吸附时间、初始Cr(Ⅵ)浓度、共存阴阳离子、光照和吸附温度等因素;在此基础上,对吸附剂FMC进行了吸附动力学和吸附热力学研究,同时对FMC进行吸附-解吸的再生研究。此外,采用XRD、N2吸附-脱附和FT-IR对硅材料FMC进行表征。实验结果表明,FMC对水中Cr(Ⅵ)具有显著的吸附作用,酸性条件利于吸附,最佳pH=1.5～2.5;共存阴、阳离子对其吸附效果几乎无影响,FMC对Cr(Ⅵ)具有很高的选择性;提高吸附温度利于FMC吸附Cr(Ⅵ),但温度的影响很不明显;光照条件大大提高了 FMC的吸附效果。FMC吸附Cr(Ⅵ)的过程符合Langmuir等温模型,光照条件下的最大拟合吸附容量为256.41 mg/g,无光照条件下最大拟合吸附容量为153.85 mg/g,吸附为吸热过程,并遵循准二级动力学模型。通过吸附性能的研究及XRD、N2吸附-脱附和FT-IR表征分析,得出FMC吸附水中Cr(Ⅵ)的吸附机理为:Cr(Ⅵ)阴离子为主要吸附对象,硅材料FMC外表面的正电荷硅物种和其内表面的铵根离子(N[CH3(CH2)15](CH3)3+)为吸附位点,吸附过程主要在酸性条件下进行;在酸性条件下,FMC表面的正电荷硅物种与内表面的铵根离子通过静电作用吸附Cr(Ⅵ)阴离子,最终以N-H键进行键合;随着pH值的升高,FMC表面的硅物种逐渐带负电荷,其与Cr(Ⅵ)阴离子的静电吸附作用减弱、甚至消失,由于溶液中大量OH-的竞争作用,FMC内表面的吸附位点对Cr(Ⅵ)阴离子的吸附作用减小,两方面原因导致Cr(Ⅵ)去除率随pH值的升高而下降。脱附为吸附的逆过程,使用碱液对FMC进行脱附解吸。在碱性解吸液中,FMC表面带有大量的负电荷,并排斥吸附在吸附剂上的Cr(Ⅵ)阴离子而释放到液相中。本课题制备的硅材料FMC吸附Cr(Ⅵ)的效果显著,且制备成本低,原料来源广泛,制备过程简单快速,在Cr(Ⅵ)废水处理方面有很大的应用前景和现实意义。
[Abstract]:Six hexavalent chromium (Cr (VI)) is a highly toxic heavy metal pollutants, teratogenicity, carcinogenicity and mutagenicity, EPA of the United States listed as water level priority pollutants, heavy metal pollutants in China is listed as the focus of prevention and control planning in 12th Five-Year ". China is a non-ferrous metal production country, industry in the production process emissions of Cr (VI) containing a large amount of waste water, chromium pollution seriously affected the safety of drinking water and industrial water production, and China is facing a severe water shortage, water pollution prevention and control of Cr (VI) is the priority among priorities of industrial wastewater treatment. The adsorption treatment of heavy metal wastewater obviously, simple operation, wide source of raw materials and can be recycled, so it is widely used in treatment of Cr (VI) wastewater. Key technologies of adsorption is the selection of the adsorbent. The different silicon source, different templates, different aging Silicon SBA-15 and MCM-41 preparation and modification methods of preparation, and as adsorbent, the adsorption of Cr by the static experiment (VI), by comparing the adsorption effect of selected optimal adsorbent. The experimental results showed that the industrial fly ash as silicon source, sixteen alkyl three methyl bromide (CTAB) as the template by alkali melt microwave aging silicon material prepared by MCM-41 (named FMC) of Cr (VI) the best adsorption effect. The mesoporous silica MCM-41 prepared by fly ash were XRD and N2 adsorptiondesorption, the results show that the material has the characteristics of mesoporous structure. But the order of the poor, small specific surface area, the reason is a lot of impurities in fly ash, in the process of preparation and distribution of materials affect the pore formation. The optimal study screened FMC adsorbent on Adsorption Properties of Cr (VI), examining the contents including the initial pH value of solution, adsorption time, initial Cr (VI). Of co existing ions, adsorption temperature and light factors; on this basis, the adsorbent FMC for the adsorption kinetics and Adsorption Thermodynamics Study on adsorption desorption and regeneration of FMC. In addition, by XRD, N2 adsorption desorption and FT-IR on silicon FMC by XRD. The experimental results show that the FMC, Cr in water (VI) has significant adsorption, adsorption to acidic conditions, the best pH=1.5 ~ 2.5; the coexistence of Yin, cation has little effect on the adsorption effect of FMC, Cr (VI) has high selectivity; improve the adsorption temperature on FMC adsorption of Cr (VI), but the effect of temperature it is not obvious; the light conditions can greatly improve the adsorption effect of.FMC adsorption Cr FMC (VI) process accords with Langmuir isothermal model, light conditions the maximum fitting adsorption capacity is 256.41 mg/g, the maximum fitting without illumination conditions, adsorption capacity is 153.85 mg/g, adsorption absorption The thermal process, and follow the two level dynamic model. And through the study of the adsorption of XRD, N2 adsorption desorption and FT-IR analysis, the FMC adsorption of Cr (VI) adsorption mechanism: Cr (VI) anion adsorption as the main object, the positive charge of silicon silicon material on the outer surface of FMC species and the the surface of the ammonium ion (N[CH3 (CH2) 15] (CH3) 3+) for the adsorption sites, the adsorption process is mainly carried out in acidic condition; under acidic conditions, ammonium ions on the surface of FMC positively charged silicon species and the inner surface by electrostatic adsorption of Cr (VI) anion, N-H in the final key key; with the increase of pH value of silica species on the surface of FMC has negative charge, and the Cr (VI) electrostatic adsorption of anions weaken or even disappear, because of the competition effect of a large number of OH- solution, FMC adsorption sites on the surface of the Cr (VI) reduce the adsorption of anion, for two reasons Guide Cr (VI) removal rate decreases with the increase of pH value decreased. As the inverse process of adsorption desorption, using alkali desorption and desorption of FMC in alkaline solution. In desorption, the surface of FMC with a large amount of negative charge and rejection adsorbed onto the adsorbent of Cr (VI) anion released to the liquid phase the adsorption of Cr FMC. The silicon material prepared in this project (VI) a significant effect, and low preparation cost, wide sources of raw materials, the preparation process is simple and rapid in Cr (VI) has great application prospect and practical significance of wastewater treatment.

【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ424;X703

【相似文献】