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采用一种改进的共沉淀法制备了纳米磁铁矿(Fe3O4)及Ni2+掺杂磁铁矿(Ni x Fe3-x O4,x=0.1,0.3,0.6),用X-射线衍射(XRD)、扫描电镜(SEM)、氮气物理性吸附、酸碱滴定等手段对产物进行了表征,用平衡吸附法研究了4种样品对Pb(Ⅱ)离子的吸附容量及吸附模型。结果表明,Fe3O4和3种Ni x Fe3-x O4均为近似球形的单相晶质纳米颗粒;与Fe3O4比较,Ni x Fe3-x O4的颗粒尺寸变小、表面电荷零点和pH=5.0时的表面正电荷量降低;样品的孔体积、比表面积和表面分形度以及表面羟基含量都随产物中Ni2+掺杂量的增加而升高。4种样品对Pb(Ⅱ)的等温吸附数据均适合用Langmuir模型拟合(R2=0.9942～0.9858),其相关系数的大小表现为:Fe3O4>Ni0.1Fe2.9O4>Ni0.3Fe2.7O4=Ni0.6Fe2.4O4;Freundlich模型对样品等温吸附Pb(Ⅱ)的实验数据拟合度较低(R2=0.981 3～0.947 7),4种样品的Freundlich相关系数的大小关系与Langmuir相关系数相反。初始pH=5.0时,Fe3O4,Ni0.1Fe2.9O4,Ni0.3Fe2.7O4和Ni0.6Fe2.4O4对Pb(Ⅱ)的最大吸附容量分别为6.02,6.68,7.29和8.34 mg·g-1。可见,Ni x Fe3-x O4(尤其是Ni2+掺杂量较高的产物)对水环境中重金属Pb(Ⅱ)的去除能力明显高于Fe3O4。
Nanocrystalline magnetite (Fe3O4) and Ni2 + doped magnetite (Ni x Fe3-x O4, x = 0.1,0.3,0.6) were prepared by an improved coprecipitation method and characterized by XRD, Scanning electron microscopy (SEM), nitrogen physical adsorption, acid-base titration and other means were used to characterize the products. The equilibrium adsorption was used to study the adsorption capacity and adsorption model of Pb (Ⅱ) for four samples. The results show that Fe3O4 and three kinds of Ni x Fe3-x O4 are nearly spherical single-phase crystalline nanoparticles. Compared with Fe3O4, the particle size of Ni x Fe3-x O4 becomes smaller. When the surface charge is zero and pH = 5.0 The amount of positive charge decreases; the pore volume, specific surface area and surface fractal degree of the sample and the surface hydroxyl content increase with the increase of Ni2 + content in the product. The isothermal adsorption data of Pb (Ⅱ) in all four samples fit well with the Langmuir model (R2 = 0.9942 ~ 0.9858), and their correlation coefficients are as follows: Fe3O4> Ni0.1Fe2.9O4> Ni0.3Fe2.7O4 = Ni0 .6Fe2.4O4. Freundlich model fitted the experimental data of the isothermal adsorption of Pb (Ⅱ) to a low degree (R2 = 0.981 3 ~ 0.947 7). The Freundlich correlation coefficients of the four samples were inversely related to the Langmuir correlation coefficient. The maximum adsorption capacity of Pb (Ⅱ) for Fe3O4, Ni0.1Fe2.9O4, Ni0.3Fe2.7O4 and Ni0.6Fe2.4O4 was 6.02, 6.68, 7.29 and 8.34 mg · g-1 when the initial pH was 5.0. It can be seen that Ni x Fe3-x O4 (especially the product with higher Ni2 + doping amount) has a higher capability of removing heavy metal Pb (Ⅱ) from water than that of Fe3O4.