功能化磁性纳米复合材料的制备及其对重金属离子的选择性去除机制研究

Contamination of natural water with heavy metals is a major problem and the development of effective adsorbents for its removal is increasingly recognized in these days. Realizing the attractive surface characteristics of functionalized magnetic nanocomposite, we propose to synthesize functionalized magnetic nanocomposite adsorbents with higher affinity towards Pb(II), Cr(VI) and Hg(II) from aqueous solutions. This project aim to achieves of the six-fold objectives; specifically, 1) We will consider to select appropriate synthesis methods for Fe3O4 nanoparticles and its stabilization by coating SiO2 layer; 2) We will screen out the most suitable surface modifying materials and methods to synthesize amino-，mercapto-，and carboxyl-functionalized Fe3O4 nanoparticles for the selective removal of Pb(II), Cr(VI) and Hg(II) ions; 3) We will characterize the functionalized and un-functionalized magnetic- Fe3O4 nanoparticles using various characterization techniques, and investigate their morphological, structural, chemical composition and magnetic properties; 4) We will further extensively investigate the performance of functionalized magnetic Fe3O4 nanoparticles for the selective adsorption of Pb(II), Cr(VI) and Hg(II); 5) We will elaborate in details the schematic removal mechanism and influencing factors on Pb(II), Cr(VI), Hg(II) adsorption by functionalized magnetic nanoparticles via investigating their structure-activity relationships, and establish the chelating and electrostatic attraction adsorption mechanism between heavy metals and functional groups onto the functionalized Fe3O4 nanoparticles; 6) We will further explore the separation, desorption and regeneration capacity of the functionalized magnetic nanoparticles for their successive applications and recovery of toxic metals. The broader aim of our project is to provide useful references or literature for further synthesis of effective adsorbents for heavy metals remediation with higher adsorption potential and selectivity.

本项目针对重金属离子采用常规处理难以达标的问题，制备出对Pb(II)、Cr(VI)、Hg(II)等重金属离子具有高效亲和性和选择性的功能化磁性纳米复合材料。确立磁性Fe3O4纳米颗粒的制备和进一步的SiO2包裹方法，并对其表面进行适宜的氨基、巯基、羧基等功能化修饰，制备出针对不同重金属离子去除的功能化磁性纳米复合材料；通过对功能化改性前后磁性纳米复合材料的表征，了解其形貌、结构、化学组成和磁性特性；考察功能化磁性纳米复合材料对Pb(II)、Cr(VI)、Hg(II)等重金属离子的选择性吸附特性和影响因素，通过构效关系分析，建立功能化磁性纳米复合材料的功能基团与重金属离子的表面螯合及静电吸引机制；最后探究功能化磁性纳米颗粒的磁分离和脱附再生性能。为进一步研究制备高吸附容量和高选择性的重金属离子新型吸附剂提供有益的借鉴。

本项目针对重金属离子采用常规处理难以达标的问题，以磁性四氧化三铁纳米颗粒或碳基材料为内核，通过表面SiO2包裹，以及氨基、巯基、羧基等功能化修饰等手段先后制备得到了Fe3O4@SiO2-mPD/SP、 Fe3O4@SiO2-EDTA、Fe3O4@SiO2-SH、AC@SiO2-NH2等功能化磁性纳米复合材料。采用SEM、TEM、XRD、XPS、EDS、FT-IR、TGA和Zeta电位仪等多种分析表征手段对功能化改性前后的磁性纳米复合材料进行表征，分析了其形貌、结构、化学组成和磁性特性，通过表征发现复合材料中Fe3O4保持了尖晶石结构，具有良好的热稳定性和耐酸耐碱性，且磁响应强度大，仅需30s就可从废水中有效分离。考察了功能化磁性纳米复合材料对水中Pb(II)、Cr(VI)、Hg(II)、Cu(II)、Cd(II)、As(III, V)等重金属离子的选择性吸附特性，研究了pH、反应温度、天然有机物、竞争性离子等影响因素，系统研究了其吸附热力学和动力学。探究了功能化磁性纳米颗粒的磁分离和脱附再生性能，发现所制备的磁性纳米复合材料具有较好的脱附和循环使用效果。借助FTIR、XPS等表征手段及构效关系分析，建立了功能化磁性纳米复合材料的功能基团与重金属离子的吸引机制，发现针对不同的重金属离子表现出不同吸附机理，主要包括：离子交换、络合吸附、氧化还原反应、静电吸引和物理吸附等过程，比如Fe3O4@SiO2-mPD/SP对Pb(II)吸附过程，络合吸附占主导作用，而Fe3O4@SiO2-mPD/SP对Cr(VI)吸附过程，络合吸附和氧化还原反应占主导作用。针对Hg(II)和As(III/V)等重金属离子，课题组还开发了CMC-FeS、gelatin-FeS、starch-FeS稳定化复合材料、FeS/Al2O3负载型复合材料、铁氧化物改性复合吸附材料等。上述研究对含重金属废水处理领域的基础研究及吸附剂的实际工程应用均有较大的参考价值。