过渡金属吸附剂同步去除抗生素和砷的界面反应机制与功能调控原理

Due to the extensive use of veterinary antibiotics and feed additives in the livestock and poultry farming industry, the combined contamination of antibiotics and heavy metals is becoming more and more serious in the aqueous environment. One of the pivotal issues in the development of water treatment technologies is how to remove antibiotics and heavy metals from polluted water simultaneously and efficiently under combined contamination conditions. The research object is the combined contamination of tetracycline antibiotics (TAs) and arsenic (As, a heavy metal with alterable oxidation state). Firstly, we will prepare a novel adsorbent by synthesizing and granulating composite transition-metal oxides, which can exhibit the capacities for both oxidation and adsorption. The surface characteristics and physicochemical properties of adsorbent will be investigated comprehensively, and the optimization of processing parameters for preparing this material will be conducted to improve its performance for removing pollutants. Then, we will make efforts to explain the dynamic processes for the removal TAs and As(III)/As(V) at the composite interfaces, which can oxidize and adsorb pollutants simultaneously. Besides, we will investigate the effects of water quality factors on the removal of TAs and As. Afterwards, we will concentrate on the characteristics of micro-interface reaction processes under various conditions, including the oxidation/adsorption processes, the speciation distributions, and the interactions of combined pollutants, together with their competitive/synergistic effects. Several surface characterization methods, especially the in-situ observation methods, will be performed to elucidate the changes in the surface properties of adsorbents before and after reacting with pollutants. We will analyze the functions and the transformation of the active sites on the surfaces of adsorbents during these reaction processes, and reveal the mechanisms for the simultaneous removal of TAs and As(III)/As(V). Finally, the adsorption process based on the novel adsorbent will be established and optimized for the simultaneous removal of TAs and As. Based on the aforementioned research results, the function regulation principles for this water purification technology will be proposed, which can provide scientific evidences and a theoretical basis for the simultaneous removal of TAs and As under combined pollution conditions.

由于兽药抗生素和饲料添加剂在畜禽养殖业中的大量使用，导致水环境中抗生素和重金属的复合污染状况日益严重。如何在复合污染条件下高效去除抗生素和重金属是水处理技术发展中的一个重要难题。本课题以水体中的复合污染物——四环素类抗生素（TAs）和变价重金属砷（As）为研究对象，拟制备兼具“氧化/吸附”功能的颗粒型过渡金属吸附剂，并对其活性位点进行功能表达和优化修饰；围绕复合污染物的微界面反应过程及其交互作用关系，探明吸附剂同步去除TAs&As的反应动力学特征和水质因子作用效应；以TAs与As的结合方式及形态分布规律为基础，利用多种原位表征技术，阐明材料在反应前后的表面结构性质变化特征及其对复合污染物在固液微界面上反应过程的作用机理，提出采用过渡金属吸附剂共去除TAs&As的技术原理，构建以新型吸附剂为核心的优质净水工艺及其有效调控方法，为实现对复合污染水体的高效安全处理提供科学依据和理论基础。

本项目以开发可同步去除有机&无机复合污染物的水处理材料及其工艺为目标，制备出了几种新型过渡金属氧化物材料；采用多种表征手段探究了各材料的表面功能位点特性，考察了各材料对砷的吸附特性和影响要素，并通过电镜扫描与光谱分析等手段探明了各材料的除砷机制。研究发现，铜锰复合结构不仅可以加强锰氧化物的氧化活性和再生性能，还可失去电子提供给氧气并生成超氧自由基，从而加强材料的氧化能力。.基于上述研究基础，我们研究了四环素类抗生素和砷在铜锰复合氧化物表面的吸附行为与机制，并探讨了两种污染物的竞争吸附效应。研究发现，铜锰复合氧化物对四环素类抗生素和砷的吸附机制均以表面羟基络合作用为主。此外，锰氧化物可将三价砷氧化为五价砷，并把抗生素氧化分解为小分子有机物。然而，两种污染物会对相同的吸附及氧化活性位点展开激烈争夺，这种“双重竞争效应”使得它们在复合污染条件下的去除效能都被大幅降低。.为提高对复合污染物的共去除性能，我们将铜锰复合氧化物联合过硫酸钠用于水中四环素和三价砷的同步去除，通过对比实验研究了污染物去除的反应动力学特征和水质影响规律，发现过硫酸钠的引入可以显著提升四环素和砷的去除效果。此外，我们利用界面表征手段、自由基捕获技术和降解中间产物检测方法揭示了四环素和砷的交互作用机制以及同步去除原理。四环素在该反应体系中的去除机制由单独使用铜锰复合氧化物时的吸附作用变为过硫酸钠催化降解作用。另一方面，由于过硫酸钠激活后产生了活性自由基，三价砷的氧化效果也被明显增强。铜锰复合结构的协同效应不但可以提供丰富的羟基，提高锰氧化物的氧化活性，而且可以利用其出色的电子转移效率来激活过硫酸钠以产生催化氧化效应，从而提高对复合污染物的去除效能。以上研究成果为有针对性地建立过渡金属水处理材料的制备及使用方法并实现相关工艺的优化调控提供了充分的科学依据和理论基础。