多重响应性磁性纳米粒子的构建、回用及其乳化油水分离机理

Emulsified oily wastewaters are widely found in our daily life and production activity. The emulsified oil is extremely difficult to separate from aqueous media, which causes severe environmental and ecological problems. Therefore, efficient separation of emulsified oil from wastewater is of great importance for both environmental protection and oil resources recovery. Recently, synthesis of various materials with special wettability for emulsified oil-water separation has attracted considerable attentions. However, these materials are easy to be contaminated in practical application, and their recycling technologies are complex and not eco-friendly. To overcome these defects, in this project, a series of multi-responsive magnetic nanoparticles (MNPs) with controllable surface charge and attachment energy will be fabricated to regulate their reversible adsorption and desorption behaviors on the surface of emulsified oil droplets, thereby achieving the objective of efficient demulsification and facile recycling. The graft copolymerization behavior on the surface of Fe3O4@SiO2 nanoparticles will be investigated in detail to adjust and control its grafting structure. Subsequently, adsorption and desorption behavior of the synthesized MNPs on oil droplet surface will be investigated in detail under the control of ion strength, pH and temperature; accordingly, the reversible adsorption and desorption mechanism will be illustrated, and corresponding control strategy will be established. The proposed strategy can well guide the directional fabrication of multi-responsive MNPs. On this basis, efficient separation of emulsified oil, as well as facile and durable cyclic utilization of MNPs will be ultimately achieved. The results of this project can lay the scientific and theoretical foundations for developing more advanced materials/technologies for efficiently treating emulsified oily wastewaters.

乳化油废水是生产生活中广泛存在的一类危害巨大的难处理污染物，高效分离其中的乳化油滴对环境保护与资源利用均具有重大意义。当前，基于表面特殊浸润性的乳化油分离材料在实际应用中仍存在易失效、回用工艺复杂且易造成二次污染的关键共性问题。为此，本项目拟构建界面吸附能与表面电荷可控的多重响应性磁性纳米粒子，可逆调控粒子在油滴表面的吸附-脱附行为，进而提升油水分离效率与粒子回用的便捷性。（1）系统研究Fe3O4@SiO2纳米粒子表面的接枝共聚规律，实现表面接枝结构的按需调控；（2）探究粒子在油滴表面的附着状态，以及基于体系温度、pH与离子强度调节下的吸附-脱附机理，创建可逆吸附-脱附行为的调控策略；（3）进而指导多重响应性磁性粒子的构建，最终同时实现油水的高效分离与磁性粒子持久便捷的循环利用。研究成果可为油水分离专用材料的设计、制备和乳化油废水的高效处理提供理论指导和策略支撑。

磁分离法有着工艺灵活、分离快速等优点，在乳化油水分离中展现出了优异的应用前景。本项目首先采用温度敏感单体N-异丙基丙烯酰胺（NIPAM）、pH与离子强度敏感单体甲基丙烯酸钠（SMA），通过在Fe3O4@SiO2磁性粒子表面进行接枝共聚制备了一系列阴离子型的多重响应性磁性纳米粒子。结果表明，该类磁性纳米粒子在“水包油”乳液中的油水分离效率随着pH的升高而下降，随着温度的升高先上升后下降，随着离子强度的增加而上升。通过对三个主要参数的影响机理的剖析，确立了磁性粒子只需要通过调节体系pH、温度、离子强度的再生回用途径，并展现出了优异的循环使用性能。随后，构建了一系列亲疏水程度、叔胺质子化程度不同的阳离子型pH响应性磁性纳米粒子。在Fe3O4@SiO2纳米粒子的基础上，通过接枝共聚在粒子表面分别引入聚丙烯酸二甲胺基乙酯（PDMAEA）、聚甲基丙烯酸二甲胺基乙酯（PDMAEMA）或聚甲基丙烯酸二乙胺基乙酯（PDEAEMA）分子链，制得了阳离子型pH响应性的磁性纳米粒子（M-PDMAEA、M-PDMAEMA、M-PDEAEMA）。结果表明：M-PDMAEA适用于pH4.0的酸性油水分离体系，M-PDMAEMA则更适用于pH5.0-9.0的油水分离体系，M-PDEAEMA在pH9.0-10.0的乳化油水分离体系中展现出了较宽的油水分离窗口。这三种磁性粒子均可通过pH调节实现再生，并均展现出了良好的循环使用性能。同时，研究结果表明，磁性粒子的正电荷密度与界面活性对油水分离窗口影响巨大；对于高正电荷密度的磁性纳米粒子，其较好的界面活性会加剧其狭窄油水分离窗口的形成。此外，构建了氨基硅烷/烷基硅烷混合改性或者季铵盐硅烷改性的具有阳离子特性的磁性纳米粒子，实现了“水包油”乳液与“油包水”乳液的快速油水分离。研究成果为乳化油水高效分离、磁性纳米粒子的持久便捷回用提供了理论基础和策略支撑。