微量有机污染物在铁基氧化物/水界面的吸附-降解的微观机制研究

Iron oxide/water interface is one of important micro-interfaces in surface environment of the earth. Though the adsorption and degradation of organic pollutants on the iron oxide/water interface have been studied, research systems differ from the real one. Considering the existing form of iron oxides in natural environment, we propose using Al-substutited iron oxides with different Al content and mixed iron oxides as adsorptants to investugate their interface proporties. Based on the content of Al in natural iron-bearing minerals, a series of α-Fe(Al)OOH and α-FexAl2-xO3 are prepared. Based on the morphologies of natural iron oxides, a series of γ-FeOOH/α-FeOOH and α-FeOOH/α-Fe2O3 are prepared. Paraquat, chlorophenol and methylene blue are selected as model organic pollutants due to their polarity, composition, and aromaticity differences. The aims of the present program are therefore: (1) to investigate the adsorption behaviour of trace organic pollutants in the iron-bearing mineral/water interface and discuss the effect of various factors (e.g. pH, temperature, existing state, with/without light irradiation) on the process, (2) to explore the effect of interface property of Al-substituted goethite and hematite as well as lepidrocite/goethite and goethite/hematite on both their affinity and subsequent degradation. Environmental micro-interface has important influence on the transfer and transformation of contaminants. The heterogeneous micro-interfacial process is an important scientific basis for understanding and resolving environmental problems. The results of this program will be helpful for us to evaluate concentration, fate, transport, transformation, bioavailablity as well as toxicity of organic pollutants. Consequently, extensive investigation on environmental micro-interface and its mechanism has great significance for the development of environmental science and technology.

铁氧化物/水界面是地表环境中影响有机污染物归趋的重要微界面之一，尽管已有污染物在该界面吸附降解的研究报道，但研究体系偏离实际情况。考虑到自然环境中含铁矿物的赋存形式，本项目提出以天然铁铝复合氧化物中铝含量为依据制备系列α-Fe(Al)OOH和α-FexAl2-xO3，以天然铁氧化物的形貌为参考制备γ-FeOOH/α-FeOOH和α-FeOOH/α-Fe2O3，选取不同荷电性和配位性有机污染物(百草枯、氯苯酚、亚甲基蓝)为受试物种，在近中性pH、0-40 C、有无光照条件下，研究有机污染物在含铁矿物/水界面的吸附-反应机制，探讨含铁矿物界面特性对污染物吸附亲和力及降解的影响。本项目要解决的是与环境微界面和影响污染物环境行为密切相关的基础科学问题，有助于认识天然矿物在有机污染物的滞留、迁移、转化过程中的重要作用，对环境科学与技术的发展具有重要的理论意义和实际参考价值。

本项目基于自然环境中含铁矿物的赋存形式，以天然铁铝复合氧化物中的掺杂金属含量为依据、以地表环境中铁氧化物的形貌为参考合成了系列α-Fe(Al)OOH、α-FexAl2-xO3、Al-水铁矿、γ-FeOOH和γ-Fe2O3等样品，选取不同荷电性和配位性有机污染物和重金属离子为受试物种，研究污染物在含铁矿物/水界面的吸附-降解反应机制，探讨了吸附过程热力学和动力学规律以及各种因素对吸附-降解行为的影响，揭示了含铁矿物的界面特性及污染物的理化性质对吸附-降解过程的影响规律；阐明了有机污染物在铁氧化物/水界面的降解路径和微观机制；利用MINEQL+ 4.6软件计算了铁氧化物表面强弱吸附位点的比例，获得了重金属离子吸附反应的平衡常数，评估了重金属离子在铁氧化物上吸附的结合力大小以及含铁矿物对重金属离子的锁定能力。探讨了不同形貌、不同晶体结构铁氧化物对有机污染物的吸附和催化降解性能，揭示了晶体结构与污染物之间的构效关系。探讨了以钢铁酸洗废液为原料合成各种铁氧化物的可能性以及在污水处理中的应用。本研究成果不仅可为认识自然环境中铁氧化物的形成过程提供有益参考，而且有助于客观理解自然环境中含铁矿物在污染物的控制、滞留、迁移、转化方面发挥的作用。