纳米Fe_3O_4及Ni^(2+)掺杂Fe_3O_4的制备、表征及吸附Pb(Ⅱ)的特性（英文）

Preparation, Characterization and Adsorption Characteristics for Pb(Ⅱ) of Fe_3O_4 and Ni-Doped Fe_3O_4 Nanoparticles

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 Ni-doped magnetites （NixFe3-xO4, x=0.1, 0.3, and 0.6） were prepared by a modified coprecipitation procedure, and their surface properties and application for the removal of Pb（II） ions from aqueous solutions were characterized using X-ray diffraction （XRD）, scanning electron microscopy （SEM）, nitrogen physical adsorption, potentiometric titrations and batch adsorption experiments. Results show that all the samples are single-phase crystalline nanoparticles with an approximately spherical shape. Compared to Fe3O4, the particle size, the pHpzc value and the surface charge at pH =5.0 for NixFe3-xO4 nanoparticles are decreased; and the pore volume, specific surface area （SSA）, surface fractal dimension and the content of surface hydroxyls are increased. Langmuir correlation coefficients for Pb（II） adsorption on the samples are fairly high （R2= 0.9942-0.9858） and they follow the order： Fe304〉Ni0.1Fe2.9Oa〉Ni0.3Fe.7O4=Nio.6Fez404, and those of Freundlich model are relatively low （R2=0.9813-0.9477） and the order is opposite to Langmuirs. At pH=5.0, Langmuir adsorption capacities （qmax） of Fe304, Nio.lFezgO4, Nio.3Fez704 and Ni0.6Fe2.404 are 6.02, 6.68, 7.29, and 8.34 mg·g-1, respectively. Compared to Fe304, NixFe3-xO4 nanoparticles with a high content of Ni have a higher adsorption capacity for the Pb（II） ions in aqueous solutions.