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厌氧状态下,游离态Fe(Ⅱ)(Fe(Ⅱ)aq)催化氧化铁晶相重组是重要的铁循环化学过程,其本质是Fe(Ⅱ)aq与结构态Fe(ⅡI)间的Fe原子交换,这一过程对稻田土壤和沉积物中重金属的环境行为产生重要影响,其影响机制有待于深入研究.本研究结果显示,Fe(Ⅱ)aq催化水铁矿晶相转变过程中,重金属离子Pb(Ⅱ)通过与Fe(Ⅱ)的竞争性吸附,降低了水铁矿表面吸附态Fe(Ⅱ)浓度,抑制了Fe(Ⅱ)aq与水铁矿中结构态Fe(ⅡI)之间的Fe原子交换,最终降低水铁矿晶相转变速率并改变水铁矿晶相转变途径.无Pb(Ⅱ)时,水铁矿最终转变为针铁矿和磁铁矿;Pb(Ⅱ)影响下,转变产物主要为纤铁矿,部分为针铁矿和磁铁矿.在水铁矿晶相转变过程中,部分吸附到氧化铁表面的Pb(Ⅱ)通过晶体包裹或Fe结构位取代,被形成的氧化铁结构化固定,从而降低了重金属Pb(Ⅱ)的活性.
Under anaerobic condition, the free iron Fe (Ⅱ) (Fe (Ⅱ) aq) is an important iron recycling chemical process, and its essence is the Fe atom between Fe (Ⅱ) aq and structural Fe Exchange, this process has an important impact on the environmental behavior of heavy metals in paddy soils and sediments, the mechanism of which needs further study.The results show that Fe (Ⅱ) aq catalyzes the transformation of heavy metal ions By competitive adsorption of Fe (Ⅱ) with Pb (Ⅱ), Pb (Ⅱ) reduced the concentration of adsorbed Fe (Ⅱ) on the surface of water iron ore and inhibited the interaction between Fe (Ⅱ) aq and the structural iron Fe atoms, eventually reducing the rate of crystal phase transformation and changing the crystal phase transition of water iron mineral.Without Pb (Ⅱ), the water iron ore eventually turned into goethite and magnetite. Under the influence of Pb (Ⅱ) , And the products of the transformation mainly consist of lepidocrocite and part of goethite and magnetite.Pb (Ⅱ) partially adsorbed on the surface of ferric oxide is replaced by crystals or Fe structure during the transformation of hydroalumite phase The formed iron oxide is structurally fixed, thereby reducing the activity of the heavy metal Pb (II).