铁基材料对水中银纳米的富集分离研究

发布时间：2018-08-13 08:51

【摘要】：随着纳米技术的发展,越来越多的贵金属纳米粒子被用于工业和家庭产品中,从而导致贵金属纳米粒子释放到环境中,对生态环境和生物健康造成威胁。由贵金属纳米微粒带来的环境污染问题逐渐受到了大家的重视。目前有少数的研究报道通过IER、CPE和离子交换树脂等去除和富集提取环境中的银纳米微粒(Ag NPs),但是这些方法存在操作复杂、样本量很小和富集效率较低等缺点。因此有必要开发简便高效的方法和材料富集分离水体中的Ag NPs。另外,AgNPs不仅稀有珍贵而且是有效的催化剂材料。可见寻求简便有效的方法富集分离环境中的Ag NPs并将其回收加以利用意义重大。为此,本文研究了磁性聚多巴胺(Fe_3O_4@PDA)、MOF-235以及煅烧的GO/MIL-88(Fe)对水中Ag NPs的富集分离,并将富集Ag NPs后的材料回收,探究了其对染料和4-硝基酚(4-NP)的催化性能。主要内容如下:1、我们采用简便的方法合成了Fe_3O_4@PDA核壳微球。通过XRD、FT-IR、TEM等表征手段对材料进行了表征,表征结果证明了PDA成功修饰在了Fe_3O_4表面。制得的磁性材料作为吸附剂被用于富集分离水溶液中的阿拉伯胶银纳米(GA-Ag NPs),实验研究了溶液p H、不同配体、吸附时间、GA-Ag NPs初始浓度以及离子浓度和腐殖酸(HA)对吸附的影响。结果表明,p H=10时吸附量最大,对GA配体的银纳米吸附效果最好,吸附等温线符合Langmuir模型,最大吸附量为169.49mg/g。此外,我们将吸附银纳米后的材料(Ag NPs-Fe_3O_4@PDA)回收后用于催化去除亚甲蓝(MB)。结果表明,20 m L、7.5 ppm的MB在30 min内能被完全去除,Ag NPs-Fe_3O_4@PDA不仅酸稳定性极好而且能重复使用至少8次。2、我们采用水热法一步合成了金属有机骨架材料MOF-235,并首次将其用于富集分离水溶液中的GA-Ag NPs。XRD、BET、TG、SEM、FT-IR等表征结果表明,我们成功合成出了高纯度、晶型结构完整的MOF-235,Ag NPs以团聚的形式成功的被富集到MOF-235表面。实验中,我们系统的研究了溶液p H、离子强度、HA浓度、吸附时间等对吸附过程的影响。结果表明,p H=6时吸附效果最佳,外在离子对吸附起促进作用并且离子价态越高促进作用越好,HA抑制吸附的进行,12 h后吸附达到平衡。动力学符合准二级动力学模型,等温线符合Langmuir模型,最大吸附量为155.76 mg/g。此外,吸附银纳米后的材料(MOF-235/Ag NPs)对4-NP有较好的催化效果,Ks=2.7x10-3/sec。3、我们合成了GO/MIL-88(Fe)复合材料,将其煅烧后得到了新型磁性碳材料,然后用于富集分离水溶液中的Cit-Ag NPs。GO的加入不仅提高了MOF材料的产率,而且大大增加了煅烧后材料对Cit-Ag NPs的富集效果。通过XRD、TG、SEM、FT-IR等表征手段对吸附前后的材料进行了表征,结果表明通过煅烧我们成功得到了磁性材料,Cit-Ag NPs成功的被富集到了磁性碳材料表面。实验探究了GO加入比例和煅烧温度对材料吸附效果的影响以及溶液p H、离子强度、HA浓度、吸附时间等对吸附过程的影响。结果表明GO加入比例为2.5%时材料吸附效果最好,煅烧温度设置为700℃时材料吸附效果最佳,溶液p H=6时吸附量最大,外在离子对吸附起促进作而HA对吸附起抑制作用。吸附动力学符合准二级动力学,吸附等温线符合Langmuir模型,最大吸附量为483.59 mg/g。
[Abstract]:With the development of nanotechnology, more and more precious metal nanoparticles are used in industrial and household products, resulting in the release of precious metal nanoparticles into the environment, which poses a threat to the ecological environment and biological health. The removal and enrichment of silver nanoparticles (AgNPs) in the environment by IER, CPE and ion exchange resins are reported. However, these methods have some disadvantages, such as complicated operation, small sample size and low enrichment efficiency. Therefore, it is necessary to develop simple and efficient methods and materials for enrichment and separation of AgNPs in water. Therefore, this paper studies the enrichment and separation of Ag NPs in water by magnetic polydopamine (Fe_3O_4@PDA), MOF-235 and calcined GO/MIL-88 (Fe), and the recovery of Ag NPs after enrichment. The main contents are as follows: 1. Fe_3O_4@PDA core-shell microspheres were synthesized by a simple method. The materials were characterized by XRD, FT-IR and TEM. The results showed that PDA was successfully modified on the surface of Fe_3O_4. The effects of P H, ligands, adsorption time, initial concentration of GA-Ag NPs, ion concentration and humic acid (HA) on the adsorption of Ag nanoparticles in aqueous solution were studied experimentally. The results show that 20 m L, 7.5 ppm MB can be completely removed in 30 minutes. Ag NPs-Fe_3O_4@PDA has excellent acid stability and can be reused at least 8 times. MOF-235, a metal-organic framework material, was synthesized and used for the first time to enrich and separate GA-Ag NPs. XRD, BET, TG, SEM, FT-IR and other characterization results show that MOF-235 with high purity and complete crystal structure was successfully synthesized. Ag NPs were successfully enriched on the surface of MOF-235 in the form of agglomeration. The results showed that the adsorption effect was the best when the P H was 6, and the higher the valence of the ions, the better the adsorption effect. The adsorption was inhibited by HA, and reached equilibrium after 12 hours. IR model showed that the maximum adsorption capacity was 155.76 mg/g. In addition, the adsorbed silver nanoparticles (MOF-235/Ag NPs) had a good catalytic effect on 4-NP, Ks = 2.7x10-3/sec.3. We synthesized GO/MIL-88 (Fe) composite material, calcined it and obtained a new type of magnetic carbon material, which was used to enrich and separate Ce-Ag NPs.GO from aqueous solution. The yield of MOF material was increased and the enrichment effect of calcined material on it-Ag NPs was greatly enhanced. The materials before and after adsorption were characterized by XRD, TG, SEM and FT-IR. The results showed that magnetic materials were successfully obtained by calcination, and Cit-Ag NPs were successfully enriched on the surface of magnetic carbon materials. The results show that when the GO content is 2.5%, the adsorption effect is the best, when the calcination temperature is set at 700 C, the adsorption capacity is the greatest, and when the solution P H = 6, the external ions adsorb the most. The adsorption kinetics accorded with quasi-second order kinetics, the adsorption isotherm accorded with Langmuir model, and the maximum adsorption capacity was 483.59 mg/g.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O614.122;TB383.1

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