壳聚糖改性磁性碳基吸附剂的制备及其对水中Cr(Ⅲ)-EDTA的吸附机理

Chitosan Modified Magnetic Carbon-Based Adsorbent:Preparation and Adsorption Mechanism for Cr􀃮-EDTA in Water

利用二茂铁制备磁性碳基材料(Fe3O4@C),通过壳聚糖(CS)功能化,制备CS改性Fe3O4@C复合吸附材料(Fe3O4@C-CS)。利用红外光谱(FTIR)、X射线衍射(XRD)、振动样品磁强计(VSM)、热重分析(TGA)和X射线光电子能谱(XPS)等对Fe3O4@C-CS表征分析,并通过改变浓度、温度、时间、pH和阳离子等条件系统研究对水中已配位的三价铬(Cr(Ⅲ)-EDTA)的吸附性能。结果表明Fe3O4@C已经成功被CS功能化,在pH=4.0、反应温度25℃、投加量0.4 g·L^-1时,吸附等温线符合Langmuir模型,理论最大吸附量为12.63 mg·g^-1,吸附动力学符合拟二级动力学模型,吸附行为是自发进行的吸热过程。结合吸附实验结果和XPS表征分析,静电吸附和配位作用是Fe3O4@C-CS吸附剂去除水中Cr(Ⅲ)-EDTA的主要机制。4次吸附-脱附循环后,Fe3O4@C-CS对水中Cr(Ⅲ)-EDTA仍具有较高的吸附效率。

The magnetic carbon-based material(Fe3O4@C)was prepared by using ferrocene,and chitosan(CS)modified Fe3O4@C composite adsorbent(Fe3O4@C-CS)was prepared.The characterization of Fe3O4@C-CS by nfrared spectroscopy(FTIR),X-ray diffraction(XRD),vibrating sample magnetometer(VSM),thermogravimetric analysis(TGA)and X-ray photoelectron spectroscopy(XPS),and the adsorption performance for Cr(Ⅲ)-EDTA in water was systematically studied by initial concentrations,adsorption temperature,time,solution pH and cations.The results show that Fe3O4@C has been successfully functionalized by CS.Adsorption isotherm was in accordance with the Langmuir model and the theoretical maximum adsorption capacity was 12.63 mg·g^-1 at 25℃,pH=4.0 and dosage of 0.4 g·L^-1.The adsorption kinetics can be fitted well with the pseudo-second kinetic model,and adsorption behavior is a spontaneous endothermic process.Based on the XPS analysis and adsorption experiments,the electrostatic interaction and surface complexation was the main mechanism of Cr(Ⅲ)-EDTA adsorption on Fe3O4@C-CS adsorbent.After four adsorption and desorption cycles,Fe3O4@C-CS still had high adsorption efficiency for Cr(Ⅲ)-EDTA in water.