过渡金属离子与高分子载体、氨配体间空间匹配及其在高含盐氨氮废水处理中应用

Ion exchange and adsorption technology has the advantages of selectivity to ammonia nitrogen, recycling of adsorbents, simple operation, small area and so on. But the salt environment has a great influence on the performance of ion exchange adsorbents. The aim of this project is to clarify the spatial matching relationship between transition metal ions, polymer carriers and ammonia ligands, and solve this problem with the aid of coordination action of transition metal ions. The binding mechanism of transition metal ions with polymer carriers will be analyzed. The influence of the existence of ammonia ligand on the structure and properties of transition metal ions and polymer carriers is studied. The complexation mechanism of ammonia nitrogen and transition metal ions in high salt waste water will be revealed. The relationship between the functional group of transition metal based polymer support and the adsorption capacity of target ligand NH4+-N will be analyzed by means of Donnan membrane effect. The synergistic effect of the resin and metal ions would be played to the maximum, so that it can selectively effect ammonia nitrogen in the wastewater. The competitive effect of salt ions on the ammonia ligands is studied to avoid the influence of coexisting ions to the maximum extent. It will break through the bottleneck of the transition metal ions fall off from the polymer carrier during the decomplexation process of the ammonia ligand. It provides theoretical support for the research and development of the transition metal based polymer carrier and its treatment process suitable for the treatment of ammonia nitrogen from saline waste water. Finally, the recycling of ligand exchange agent in the treatment of ammonia nitrogen from saline wastewater will be realized.

离子交换与吸附法具有对氨氮的选择性、吸附剂可以再生实现循环利用、操作简单、占地面积小等优点，但盐分环境对离子交换吸附剂的性能影响非常大。本项目拟在厘清过渡金属离子与高分子载体、氨配体间空间匹配关系基础上，借助过渡金属离子的配位作用解决这一问题。将剖析过渡金属离子与高分子载体的结合机制，分析氨配体的存在对过渡金属离子与高分子载体结构、性能的影响，揭示高含盐废水中氨氮与过渡金属离子的络合机制；借助道南膜效应剖析过渡金属基高分子载体中官能团与对氨配体吸附容量的关系，以将树脂与金属离子的协同效应发挥到最大，使其选择性地对废水中氨氮产生作用；研究盐离子对氨配体的竞争作用，最大限度地避免共存离子的影响；突破氨配体解络合过程中过渡金属离子从高分子载体中脱落的瓶颈，为研发适于处理高含盐氨氮废水的过渡金属基高分子载体及其处理工艺提供理论支撑，最终实现配体交换剂在高含盐氨氮废水处理中的循环利用。

国务院印发的《“十三五”生态环境保护规划》再次将氨氮作为污水减排的约束性指标。离子交换与吸附法具有对氨氮的选择性、吸附剂可以再生实现循环利用、操作简单、占地面积小等优点，但盐分环境对离子交换吸附剂的性能影响非常大。项目选用四种高分子载体（阳离子交换树脂D001、螯合树脂D751、蒙脱石、硅藻土）分别负载四种过渡金属（Co、Ni、Cu、Zn），制备成金属基高分子载体。研究了盐共存条件下不同高分子载体吸附剂对氨氮的吸附性能及其作用机制。金属基树脂/蒙脱石/硅藻土除氨氮主要是存在氨气分子与金属离子间（即吸附剂与吸附质间）的电子转移，主要是氨分子与金属离子间的配位络合。.但在氨配体解络合过程中，解吸剂会破坏载体与过渡金属间的稳定性，使被负载的金属从载体上脱落，如Cu+Ni-D751解吸过程中Ni2+三次解吸脱落量都大于1%，不仅造成金属污染，还使吸附剂分离性能降低，因此研究负载金属稳定性以及金属利用率对循环处理高含盐废水至关重要。基于解吸过程金属脱落的问题，对金属负载型树脂进行改性处理，得到Cu-D751-NaOH、Cu+Ni-D751-NaOH 与Cu+Zn-D751-NaOH。当溶液初始pH为11，树脂投加量6 g/L，氨氮初始浓度100 mg/L，NaCl浓度4 g/L，反应时间2.5 h，三种改性金属负载型树脂的氨氮吸附量最大10.53 mg/g。使用NaCl溶液作为解吸剂，发现解吸过程中Cu-D751-NaOH中Cu2+脱落量始终小于Cu-D751，表明NaOH改性能够提高D751树脂负载Cu2+的稳定性。表征分析可知，改性金属负载型树脂上负载金属主要以金属氢氧化物形态配位吸附氨氮，改性后负载金属由聚结变分散，有利于负载金属与氨氮的结合，提高金属利用率。说明通过改变负载金属在树脂上的存在形态，提高了配体交换吸附剂吸附性能及稳定性，从而解决配体交换吸附剂在解络合过程中负载金属脱落的问题。实际高含盐氨氮废水处理结果表明，三种改性金属负载型树脂的吸附性能较好，实际废水中共存离子影响较小，且对实际高含盐氨氮废水的吸附性能较稳定，最终实现配体交换剂在高含盐氨氮废水处理中的循环利用。