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游离态Fe(Ⅱ)与磁铁矿的相互作用对环境污染物具有较强的还原活性。在自然界中,磁铁矿结构中的Fe~(2+)和Fe~(3+)常被过渡金属类质同像置换,显著改变磁铁矿的结构特征,物理化学性质和表面反应性。本研究考察了锌类质同像置换对磁铁矿与Fe(Ⅱ)共存体系去除Cr(Ⅵ)活性的制约及其机制。系列锌置换磁铁矿(Fe_(3-x)Zn_xO_4,x=0,0.25,0.49,0.74和0.99)用共沉淀法制备,并用XRD、TG、比表面积、酸碱滴定等方法进行系统的结构和物理化学性质表征。研究结果表明:系列锌置换磁铁矿样品具有尖晶石结构,Zn置换没有明显改变磁铁矿的晶体结构。比表面积和表面位密度随Zn置换量的提高而逐渐增大。在中性条件下,Cr(Ⅵ)快速吸附到磁铁矿表面,然后逐渐被磁铁矿及其表面吸附态Fe(Ⅱ)还原,最终固定在磁铁矿表面。随着Zn置换量的增加,磁铁矿与Fe(Ⅱ)共存体系对Cr(Ⅵ)的去除效率呈现先降低,后提高的变化趋势,这主要归因于共存体系对Cr(Ⅵ)还原能力的降低和吸附能力的提高。
The interaction of free Fe (II) with magnetite has a strong reduction activity to environmental pollutants. In nature, Fe2 + and Fe3 + in the magnetite structure are often replaced by the same type of transition metal, which significantly changes the structural characteristics, physicochemical properties and surface reactivity of the magnetite. In this study, we investigated the inhibition of Cr (Ⅵ) removal by magnetite and Fe (Ⅱ) coexisting system and its mechanism. Series of zinc-substituted magnetite (Fe_ (3-x) Zn_xO_4, x = 0,0.25,0.49,0.74 and 0.99) were prepared by coprecipitation method and the structure of the system was characterized by XRD, TG, specific surface area and acid-base titration And physico-chemical characterization. The results show that the series of zinc-substituted magnetite samples have spinel structure, Zn substitution did not significantly change the crystal structure of magnetite. The specific surface area and surface density increased gradually with the increase of Zn substitution. Under neutral conditions, Cr (Ⅵ) adsorbs rapidly to the surface of magnetite, and then is gradually reduced by the adsorbed Fe (Ⅱ) on the magnetite and its surface and finally fixed on the surface of the magnetite. With the increase of the amount of Zn substitution, the removal efficiency of Cr (Ⅵ) decreased firstly and then increased after Co (superscript 2 +) coexisted with magnetite and Fe (Ⅱ), which was mainly attributed to the reduction of Cr (Ⅵ) The reduction and the improvement of adsorption capacity.