Abstract: A new magnetic nanoadsorbent（Fe3O4@SiO2@CMC）was fabricated by coating silica from the hydrolysis of sodium silicate onto the surface of magnetic Fe3O4 nanoparticles，and followed a covalent binding of high-deacetylated-degree carboxymethylated chitosan onto the surface of Fe3O4@SiO2 nanoparticles via carbodiimide activation. The obtained magnetic nanoadsorbent（Fe3O4@SiO2@CMC）was characterized by TEM，IR，XRD and VSM. And the adsorption properties of the adsorbent for Cr(Ⅵ) ions were also investigated. The results showed that the adsorption capability was significantly affected by pH，and the adsorption capacity was best at pH=2；Moreover，with the distributions of Cr(Ⅵ) species under corresponding pH conditions，the adsorption mechanisms of Cr(Ⅵ) including both ion exchange and electrostatic gravitation were discussed. In addition，adsorption equilibrium data were correlated with Langmuir and Freundlich isotherms to determine the adsorption potential. The results showed that the Langmuir isotherm was better relative to the Freundlich isotherm，and a maximum absorption capacity of 86.96 mg/g and a Langmuir adsorption equilibrium constant of 0.0174 L/mg at 298 K，pH 2 with volume of 5 mL.

Key words: magnetic nanoadsorbent, heavy metal ions, absorption, langmuir isotherm

摘要： 先通过硅酸钠水解在磁性Fe₃O₄纳米粒子表面包覆二氧化硅，制得磁性硅粒子（Fe₃O₄@SiO₂）；然后再通过碳二亚胺活化接枝法在Fe₃O₄@SiO₂纳米粒子表面接枝高脱乙酰度羧甲基化壳聚糖（CMC），制备了一种新型磁性纳米吸附剂（Fe₃O₄@SiO₂@CMC）。通过透射电镜（TEM）、红外光谱（IR）、X射线衍射（XRD）以及振动样品磁强计（VSM）对其进行了表征，着重研究了其对水中Cr(Ⅵ)离子的吸附性能。结果表明：溶液的pH值能显著影响吸附剂对Cr(Ⅵ)离子的吸附效果，pH值为2时效果最佳。结合相应pH值下Cr(Ⅵ)的形态分布，探讨了这种新型材料对Cr(Ⅵ)的吸附机理。结果表明：其吸附机理及吸附容量与Cr(Ⅵ)的离子形式有关，吸附过程以离子交换与静电引力为主。吸附平衡数据分别采用了Langmuir和Freundlich方程进行拟合。结果表明，等温吸附数据更符合Langmuir 模型，T＝298 K、pH＝2、V＝5 mL时，吸附剂的饱和吸附容量q_m＝86.96 mg/g，吸附常数为0.0174 L/mg。

关键词: 磁性纳米吸附剂；Cr(Ⅵ)；吸附, Langmuir模型