异化还原驱动的铁氧化物在人工湿地基质床体内扩散沉降及其对典型抗生素的吸附去除

Constructed wetland has been employed increasingly in advanced treatment and reusing of wastewater. Sorption to contaminant is the main function of constructed wetland. But the adsorption capacity of usual substrates is not high. Iron oxide has strong adsorption to ionic pollutants, such as antibiotic, heavy metal in wastewater. And it is easily transferred and moved by redox reaction. Based on both features of iron oxide, a new way improving the adsorption of wetland bed made up of usual substrate is presented in this project. It is as described in the next. The Fe(Ⅲ) in the material containing rich iron will be converted into Fe(Ⅱ) by microbiological iron dissimilatory reduction with organic existing. Fe(Ⅱ), which has more strong mobility, will be easily brought out by water flow. Then, it can diffuse in the constructed wetland bed and was deposited on the surface of the substrate particle by regulating the water low. The iron oxide particle newly formed in the substrate bed will increase the adsorption capacity of whole wetland. .The diffusion and settling of Fe(Ⅱ) from microbiological iron dissimilatory reduction in the wetland substrate bed will be researched firstly. The characterization and type of the iron oxide particles newly formed is the emphasis. Two objects are be expected, (1) the diversity of the iron oxide newly formed particles, (2) key factor controlling different types. Based on the results above, the adsorption of the substrate with newly formed rion oxide to two typical antibiotic, tylosin and sulfamethazine, will be investigated. The sorption effect, mechanism and impact factors will be determined. Finally, the type of iron oxide which could efficiently bind the antibiotics will be screened out.

吸附滞留是人工湿地重要的污染物去除性能，但常规基质构建的系统吸附性不强。铁氧化物对抗生素、重金属等离子型污染物具有较强的吸附，且易通过氧化还原进行迁移转化。本研究基于铁氧化物这两个特性，提出强化人工湿地常规基质吸附性能的新思路，即利用异化还原作用，将富铁基质中三价铁转变为迁移性较好的亚铁，通过调控湿地水流和水质，使其迁移扩散到常规基质床体中然后氧化沉降，再次形成吸附性能较强的铁氧化物，进而提高人工湿地常规基质床体对抗生素等污染物的吸附去除性能。.研究首先分析异化还原溶出的亚铁在常规材料构建的基质床体内扩散沉降特点，重点研究不同影响因素下形成的铁氧化物的形态特征，探讨沉积形成的铁氧化物多样性并阐明影响沉积形态的关键因子。在此基础上，分析铁氧化物强化后基质对2种典型抗生素磺胺二甲基嘧啶和泰乐菌素的吸附去除效应、机制及影响因素，明确可对污水中残留抗生素高效去除的铁氧化物形态及关键影响因子。

本研究针对人工湿地常规基质材料吸附性能差、富铁基质中铁氧化物吸附性能强但不易被充分利用问题，探索利用微生物驱动的铁还原和氧化沉降将富铁基质中铁氧化物迁移到常规基质床体中，进而提升常规基质床体的污染物吸附性能。围绕上述研究目标，开展了以下4部分研究，铁还原溶出的亚铁在常规基质床体内扩散沉积影响因素；陶粒基质床体内扩散沉积的铁氧化物组成及形态多样性分析；铁氧化物扩散沉积对基质床体污染物吸附性能的强化及吸附能力再生；铁氧化物负载陶粒活化过硫酸盐氧化去除抗生素和亚甲基蓝的效果及机制。研究发现基质颗粒粒径、亚铁氧化沉降反应pH和基质材料表面粗糙度是影响亚铁沉降的3个关键因素，普通建筑陶粒比砾石更适宜亚铁氧化沉降及黏附，亚铁厌氧氧化的间歇运行方式是更加经济性和高效的铁迁移优化方法。同样，氧化反应类型是影响黏附（负载）在陶粒表面铁氧化物形态的关键因素，亚铁厌氧氧化形成的负载陶粒是微生物细菌与铁氧化物共絮凝沉降过程形成的，表面覆盖层更加疏松多孔，对陶粒吸附性能提升也优于好氧氧化负载的陶粒，相比原始陶粒对磷、砷、镉和泰乐菌素、亚甲基蓝吸附性能都有较大幅度提升，对砷、磷的提升幅度最高，分别达到75%和95%；除了泰乐菌素外，厌氧源的铁氧化物负载陶粒的吸附都是典型的化学吸附，短时间内达到吸附平衡，吸附速率快；厌氧源铁氧化物负载陶粒表面铁是二价和三价混合，可以活化过硫酸盐产生硫酸根自由基、羟基自由基、超氧自由基氧化去除泰乐菌素、磺胺二甲基嘧啶和亚甲基蓝。吸附饱和后的铁氧化物负载陶粒再生可以原位进行，对于磷、砷、镉，可以通过再次铁迁移覆盖原有的迁移层恢复吸附能力，对于亚甲基蓝等有机物可以通过活化过硫酸盐进行类芬顿反应恢复吸附能力。本研究成果在人工湿地常规基质床体污染物吸附性能原位提升与再生方面具有重要的应用前景。