铁纳米线对水中Cu2+的吸附性能及机理

为研究nZVI（纳米零价铁）材料对水中Cu2+的吸附性能，采用液相还原法合成核壳结构的nZVI，即FSCNs（铁纳米线，Fe@Fe₂O₃ core-shell nanowires）.通过批处理吸附试验研究pH、离子强度、FSCNs投加量、反应时间、初始ρ（Cu2+）、反应温度等因素对Cu2+去除率的影响，运用动力学模型、等温吸附模型和吸附热力学模型分析FSCNs对Cu2+的吸附特性，并利用SEM（扫描电镜）、XRD（X射线衍射）和XPS（X射线光电子能谱）等表征手段探讨FSCNs对Cu2+的吸附机制.结果表明:①在pH为5、离子强度为0.01 mol/L、FSCNs投加量为0.5 g/L、反应温度为318 K条件下，FSCNs对Cu2+产生的吸附容量最大，为387.6 mg/g.②FSCNs对Cu2+的吸附反应在30 min内达到吸附平衡，此时的最大吸附率可达96%；FSCNs对Cu2+的吸附更符合准二级动力学模型（R2≥0.992），表明化学吸附可能为该反应的限制步骤；Langmuir和Freundlich等温吸附模型均能较好地拟合吸附结果（R2≥0.992）；该吸附过程是自发的吸热反应〔ΔG0（吉布斯标准自由能） < 0，ΔH0（标准焓变）>0〕.③大部分Cu2+在加入FSCNs后转化为Cu、Cu₂O和CuO，被吸附在FSCNs表面，吸附、还原与共沉淀可能是FSCNs去除水中Cu2+的主要机理.研究显示，FSCNs对Cu2+的最大吸附容量为387.6 mg/g，能快速高效吸附水中的Cu2+，应用前景良好. 

Adsorption Performance and Mechanisms of Cu2+ from Aqueous Solution by Fe@Fe2O3 Core-Shell Nanowires

In order to study the adsorption behavior of nanoscale zero valent iron (nZVI) material for removal of Cu2+ in aqueous solution, a specific nZVI, Fe@Fe₂O₃ core-shell nanowires (FSCNs), was synthesized through the reduction of ferric ions by sodium borohydride. The effects of pH, ionic strength, dosage of FSCNs, contact time, initial ρ(Cu2+) and temperature on Cu2+ adsorption on FSCNs were studied by the batch sorption experiments. The adsorption characteristics of Cu2+ on the FSCNs were studied by adsorption kinetics, adsorption isothermal model and adsorption thermodynamics. Besides, the adsorption mechanism of Cu2+ on the FSCNs was analyzed by scanning electron microscope (SEM), X-ray Diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results demonstrated that: (1) The maximum adsorption capacity of Cu2+ on FSCNs was 387.6 mg/g at pH 5, ionic strength of 0.01 mol/L, dosage of FSCNs of 0.5 g/L and at 318 K. (2) Adsorption equilibrium can be reached within 30 min with the maximum adsorption rate of 96%. Adsorptions of Cu2+ on the FSCNs could be better described by the pseudo-second-order-model (R2≥0.992) and the Langmuir and Freundlich models (R2≥0.992), which indicates that chemisorption may be the limiting step of the reaction. Thermodynamics results show it is a spontaneous endothermic reaction (standard Gibbs free energy (ΔG0) < 0, standard enthalpy (ΔH0) > 0). (3) Most of the Cu2+ was transferred to Cu, Cu₂O and CuO. And the reduction and co-precipitation should be the main mechanism of the Cu2+ removal from aqueous solution by FSCNs. The study suggests that FSCNs has a maximum adsorption capacity of 387.6 mg/g, it can rapidly and efficiently remove Cu2+ from aqueous solution, and can be applied in practice in the future.