两亲型壳聚糖基絮凝剂的构建、磁功能化及其絮凝机理

Chitosan (CS), a natural polyelectrolyte, is one of the most promising candidates as the flocculants in the wastewater treatment. However, during the process of oily wastewater treatment with CS, the coagulation of oil droplet occurs mainly due to the charge effect, as a result, it exhibits a very narrow flocculation window; meanwhile, the separation efficiency of floc is also very low. To overcome these defects, a kind of amphiphilic and cationic flocculant will be fabricated by grafting a neutral monomer, acrylamide (AM), and a cationic monomer with moderate hydrophobicity, dimethyl acryloyloxyethyl benzyl ammonium chloride (DBC), onto CS. Subsequently, the flocculation performance and mechanism of the CS-based flocculants with various grafting structure in the oily wastewater treatment will be clarified; meanwhile, the influences of key factors on the flocculation performance and the control strategy will be illustrated. On this basis, to improve the separation efficiency of floc in water, a kind of magnetic CS-based flocculants will further be fabricated via binding the CS-based graft copolymer on the Fe3O4 nanoparticle surface. Thereafter, the flocculation mechanism in the oily wastewater treatment with magnetic flocculants will be examined in the absence or presence of magnetic field. The intrinsic relationship of the molecular structure of magnetic flocculant, flocculation mechanism and flocculation efficiency in the oily wastewater treatment will be thoroughly clarified. By adjusting and controlling the molecular structure of the flocculants, highly efficient treatment of the oily wastewater will be achieved. These research results can take an important guiding role in the design and fabrication of magnetic flocculants, as well as the improvement of the oily wastewater treatment.

为克服壳聚糖（CS）在含油污水处理中絮凝窗口窄、絮凝机制单一、絮体分离效率低的缺陷，本项目拟将丙烯酰胺（AM）与具有一定疏水性的阳离子单体丙烯酰氧乙基二甲基苄基氯化铵（DBC）通过接枝共聚引入到CS侧链上，构建两亲型壳聚糖基絮凝剂；明确不同接枝结构絮凝剂在含油污水处理中的絮凝效果与絮凝机理，揭示影响絮凝效果的关键因素及其调控策略。在此基础上，为进一步提高絮体分离效率，将上述两亲型絮凝剂绑定到Fe3O4纳米粒子上，构筑磁性壳聚糖基絮凝剂。研究磁性絮凝剂在有无磁场介入下的絮凝效率与絮凝机理，揭示絮凝剂结构-絮凝机理-絮凝效率之间的内在关联，最终通过调控絮凝剂分子结构，优化含油污水处理效率。研究成果可为磁性絮凝剂的设计制备和乳化油污水的处理提供理论基础和策略支撑。

本项目从分子结构设计与相互作用角度出发，通过壳聚糖（CS）与丙烯酰氧乙基二甲基苄基氯化铵（DBC）或丙烯酰胺（AM）单体的接枝共聚构建了两亲型壳聚糖基絮凝剂，系统研究了其接枝共聚规律，实现了絮凝剂分子结构调控。研究了壳聚糖基絮凝剂在乳化油废水处理中的絮凝效果，建立了絮凝剂分子结构与絮凝效率之间的构效关系。当PDBC分子链接枝到CS分子链骨架后，絮凝窗口显著拓宽，絮凝效率随着PDBC接枝率的增加而进而升高；而引入PAM接枝链后，絮凝效率下降。经优化后的CS-g-PDBC处理后，油类物质的去除率可达到97.5%以上，含油废水的浊度去除率可达到99.0%以上。此外，也采用zeta电位法对絮凝机理进行了研究，结果表明CS-g-PDBC在酸性与中性条件下，其絮凝机理为静电簇与吸附架桥机理；而在碱性条件下，其絮凝机理为电中和与吸附架桥机理。..为进一步优化破乳效率，将季胺化壳聚糖（QC）接枝到氨丙基改性的磁性纳米粒子（Fe3O4@SiO2-NH2）表面，制得了一系列磁性纳米絮凝剂Fe3O4@SiO2-QC。首先研究了Fe3O4@SiO2-NH2的破乳效果，结果表明：在酸性条件下，氨丙基改性的磁性纳米粒子带正电荷且具有两亲性，可以通过静电作用和表面活性吸附到乳化油滴表面，并进一步絮凝油滴，最终在磁场作用下快速分离絮体；在中性条件下，Fe3O4@SiO2-NH2粒子不带电荷，但可通过表面活性聚集在油水界面，最终通过磁场实现油水分离。在碱性条件下，粒子和电荷之间存在较强的静电排斥作用，无法进行有效的油水分离。在此基础上，研究了Fe3O4@SiO2-QC的乳化油水分离效果与机理。当Fe3O4@SiO2-QC加入到乳化油废水体系后，Fe3O4@SiO2-QC表现为一种磁性纳米絮凝剂，磁性粒子可通过静电簇机理高效絮凝乳化油滴形成大量絮体。磁场可加快絮体分离，也可在粒子添加过量时分离重新分散的乳化油滴以及游离的磁性粒子，从而进一步提升乳化油水分离效率。研究成果为磁性絮凝剂的设计制备和乳化油废水的高效处理提供了理论基础和策略支撑。