磁树脂耦合强化混凝去除复合水体微污染有机物的行为和机制研究

To resolve the problems caused by organic micro-pollutants (pharmaceuticals and personal care products, endocrine disrupters, et al) in water security, magnetic ion exchange (MIEX) with excellent anion adsorption capacity is combined with enhanced coagulation, which could remove hydrophobic and macromolecular organic compounds efficiently. The combined process is designed to remove organic micro-pollutants with different properties, depending on the complementary roles of MIEX resin and coagulation. The project focuses on the efficiencies and mechanisms of organic micro-pollutants removals in composite-polluted waters. Removal efficiencies of organic micro-pollutants by MIEX resin-enhanced coagulation process are evaluated in presence of natural organic matters (NOMs), and the molecular weight distribution, characteristics of function groups as well as floc structures and surface electrical properties are examined to clarify the removal mechanisms of organic micro-pollutants. Effects of MIEX resin on floc characteristics are investigated. On the basis of MIEX resin pre-treatment, coagulation is optimized by adjusting the coagulant type, matching the preferential species, controlling the doses and pH, and the enhanced coagulation models matched with organic micro-pollutants of different characteristics are illuminated. This work provides novel idea and technology for the micro-polluted water treatment, and could increase the removal efficiencies of organic micro-pollutants removals as well as help explore the removal mechanisms, which is of significantly theoretical and practical value.

针对目前水质安全保障的突出问题—微污染有机物（药品与个人护理用品、内分泌干扰物等）的去除，本项目拟利用磁树脂（MIEX）对带负电物质良好的吸附性能，联合强化混凝对大分子疏水性有机物的絮凝作用，功能互补，实现对不同特性微量有机物的强化去除。项目着力于微污染有机物在复合污染水体中的去除效果和机制研究，探讨在天然有机物（NOMs）共存条件下，MIEX树脂耦合强化混凝对微污染有机物的去除效果，结合对水样分子量分布、官能团特征及絮体结构、表面电荷等的实时监测，阐明微污染有机物的去除机制；考察MIEX树脂对絮体特性的影响，并在MIEX预处理条件下，针对性地采取混凝剂筛选、优势形态匹配、投量和pH控制等强化混凝措施，明确与不同特性微污染有机物相匹配的强化混凝模式。本项目在微污染水源水处理方向提出新思路和新方法，有望在微污染有机物强化去除和机制认识方面取得突破，具有理论和实际应用价值。

本课题利用强化混凝、磁树脂（MIEX）及其联用技术，对复合污染水体中微量有机物的物化特性与其在水处理过程的作用机制和效果之间的构效关系进行研究。结果表明，在混凝剂投加量充足条件下，微污染有机物pKa值越大，强化混凝效率越高；有机物去除率和其pKa、log Kow和log Koc值之和呈正线性相关。电中和作用在投药量低时对胶体的脱稳起关键作用，而中、高投药量下的主要混凝机制是铝盐水解产物对污染物的吸附架桥和网捕卷扫作用。复合污染水体中的HA在混凝过程中扮演“纽带”角色，通过氢键、范德华力、ππ作用等发挥吸附、裹挟作用促进微量有机物的去除。低投药量下的主要混凝机制为微量有机物在共存HA上的协同去除，去除率和pKa、logKow和logKoc均呈正相关关系，且聚合氯化铝（PACl-1、PACl-2）较硫酸铝（AS）的混凝效果好；而中、高投药量下微污染有机物、HA和铝盐水解产物间的相互吸附作用同时存在，疏水性强的微污染有机物去除效率高，三种混凝剂对有机物的去除率相差小。与单一体系比，复合污染体系混凝生成的絮体粒径较小，但分形维数高，结构更加密实、紧凑。相反，MIEX对pKa小、Kow大的微量有机物去除率较高。pKa值越小，离子交换作用越显著，Kow值越大，疏水性吸附作用越强。分子结构的酚羟基能够促进微量有机物与MIEX发生有效离子交换作用。HA对微污染有机物在MIEX上的离子交换和微孔吸附过程具有抑制作用，从而使有机物去除率明显下降。微量有机物的pKa值越大，Kow和Koc值越小，HA对其在MIEX上吸附过程的影响越严重。以分子形态存在、疏水性强的微污染有机物易被HA吸附；分子结构中含有羧基、芳香环、酚羟基结构的有机物在HA上的吸附率也高。微污染有机物对HA在混凝或MIEX单元的去除效率均未产生明显影响。与单独工艺相比，MIEX和混凝联用对复合体系中污染物的去除率有显著提高。混凝作为预处理工艺对HA的有效去除可有效缓解其在MIEX上的竞争吸附作用，因此相同条件下混凝-MIEX较MIEX-混凝对微污染有机物的去除效率高，而两种组合对HA的去除率基本一致。