载纳米Fe(Ⅲ)双功能复合吸附剂的研制及其同步去除生化尾水中磷和硝酸根的研究

It is widely accepted that excessive loadings with phosphorus and nitrogen in waters are the major causes of eutrophication, which indicate that eutrophication control should focus on simultaneous reduction of both nutrients. Generally, phosphate and nitrate in the effluent of municipal wastewater treatment plants usually fail to meet relevant national standards, and thus, co-removal of phosphate and nitrate from the effluent becomes the primary task to mitigate eutrophication. Adsorption/ion exchange is one of the most widely used processes, unfortunately, most of the available adsorbents/ion exchange materials are not capable of simultaneously selective removal of phosphate and nitrate from wastewater. Some related studies have demonstrated that nitrate could be selectively captured by anion-exchange resins with long alkyl chain of the quaternary ammonium groups, and phosphate could be preferably sequestrated by nanosized hydrated ferric oxide. As inspired by the above study, this project will design and fabricate a novel bifunctional hybrid adsorbent by immobilizing nanosized hydrated ferric oxide into the anion-exchange resin. The resultant hybrid adsorbent is expected to simultaneous removal of phosphate and nitrate from bio-treated municipal sewage. The main focus of this project aims to examine the performance of the resultant hybrid adsorbent for the simultaneous removal of phosphate and nitrate, reveal the underlying mechanism responsible for co-removal, understand the the effect of ambient conditions and coexistent matters on the performance of the hybrid adsorbent. And on this basis, systemic research will be focused on high efficiency regeneration of the adsorbent for repeated use. We believe this study propsed here is significant and novel, and could provide the scientific and technical supports for the simultaneous removal of phosphate and nitrate from bio-treated municipal sewage base on hybrid material adsorption.

水体中超负荷的氮、磷等营养物质是造成水体富营养化的主要因素，同时削减氮、磷的排放是控制水体富营养化的重要举措。本项目针对我国城市污水厂生化尾水中氮、磷不能稳定达标，而现有吸附/离子交换材料难以同步选择性去除污水中磷和硝酸根的现状，拟耦合表面修饰长烷基链季胺基的阴离子交换树脂对硝酸根的选择性吸附性能和纳米Fe(Ⅲ)氧化物对磷的高效去除性能，将纳米Fe(Ⅲ)氧化物均匀固载到具有选择性除硝酸根功能的树脂载体孔道内，研制能同步选择性去除生化尾水中磷和硝酸根的双功能复合吸附剂，系统研究复合吸附剂同步去除生化尾水中磷和硝酸根的性能与机理，揭示环境条件和生化尾水中常见共存物质对其吸附性能的影响规律与作用机制，在此基础上研发复合吸附剂的高效脱附再生技术，考察其连续“吸附-再生”性能，为开发基于复合材料吸附的生化尾水同步脱氮除磷技术提供理论参考与技术支持。

污水处理厂的生化尾水水量大，且含有种类繁多的微量污染物，深度处理是实现其提标排放或回用的必然要求。生化尾水中氮、磷以及溶解性有机物（Dissolved organic matter, DOM）的高效去除是实现其深度处理的核心与关键。本研究的主要目标是制备新型的纳米复合吸附材料用于生化尾水中氮、磷和溶解性有机物的深度去除。. 首先，在系统解析不同来源焦化废水生化尾水中DOM的组成和性质的基础上，制备出一种氨基化复合吸附材料A-HPA用于生化尾水中DOM的深度去除。该材料为苯乙烯-二乙烯苯骨架结构，具有较高的比表面积、丰富的纳米孔结构和叔胺功能基团，能够通过π-π作用、微孔填充作用和酸碱作用，协同吸附去除生化尾水中的DOM。与两种商业化吸附树脂D-301和NDA-150相比，A-HPA对生化尾水中DOM的去除效率最高，且吸附饱和的树脂可以用NaOH-NaCl溶液进行原位再生，从而实现多批次循环吸附操作。. 其次，论文以FeCl3浓度为控制因素，通过“离子交换-原位沉积”法制备了四种载铁量分别为5.4%、9.8%、12.3%和16.7%的复合材料A-HPA@HFO-X（X代表复合材料载铁量）。结果表明，提高FeCl3浓度有利于提高复合材料的铁含量，而铁含量的变化对复合材料的孔结构、比表面积，HFO颗粒的大小和分散性具有显著影响。过高或过低的铁含量均不利于复合材料去除P性能的发挥，A-HPA@HFO-9.8具有最佳的去除P的性能。. 最后，本研究采用三乙胺对聚苯乙烯树脂进行化学修饰，制得季胺化的阴离子交换树脂PRT，继而以PRT为母体将纳米Fe（Ⅲ）载入PRT孔道内，制得载纳米铁复合吸附剂HFO@PRT。HFO@PRT优异的同步脱氮除磷性能源于其独特的结构：固载的纳米HFO颗粒能够通过内配位络合作用实现对磷的选择性吸附，而树脂母体上修饰的三乙胺则能够通过静电和离子交换作用实现对硝酸盐的选择性吸附。吸附饱和的HFO@PRT能够通过NaOH-NaCl混合溶液实现高效原位再生，再生后吸附性能没有明显下降，从而实现多批次循环吸附操作。柱吸附实验表明，HFO@PRT能将生化尾水中的硝酸盐和磷分别由20mg/L和1.5mg/L降至10 mg/L和0.2 mg/L以下，在生化尾水的深度处理领域具有较好的应用潜力。