海藻酸钠水凝胶的制备及其对重金属离子吸附性能的研究

Preparation of Sodium Alginate Hydrogels and Its Adsorption Property Towards Heavy Metal Ions

中文关键词:  海藻酸钠  生物质水凝胶  重金属离子  吸附动力学

Key Words:sodium alginate  biomass hydrogel  heavy metal ions  adsorption kinetic

中文摘要:

      以海藻酸钠（SA）为基材，己二酸二酰肼（ADH）为交联剂，在常温常压条件下，通过化学交联法成功制备得到SA水凝胶。采用傅里叶变换红外光谱仪（FT-IR）、扫描电子显微镜（SEM）、热重分析（TG）等技术手段对SA水凝胶的化学结构、表面形貌、热稳定性及溶胀性能进行分析；并研究SA水凝胶对重金属离子（Cu²⁺、Pb²⁺和Cr⁶⁺）的吸附性能和吸附机理。结果表明，SA通过酰胺键（—CONH—）交联形成水凝胶网络，SA水凝胶表面呈“蜂窝状”多孔结构，热稳定性良好，溶胀率较高。在吸附温度25 ℃、重金属离子初始质量浓度50 mg/L、最佳吸附体系pH（吸附Cu²⁺和Pb²⁺时pH值=4，吸附Cr⁶⁺时pH值=3）、吸附时间480 min条件下，SA水凝胶对Cu²⁺、Pb²⁺和Cr⁶⁺的吸附性能良好，平衡吸附量分别为75.3、124.5和26.4 mg/g。动力学和热力学分析表明，SA水凝胶对重金属离子的吸附过程符合准二级动力学模型和Freundlich等温吸附模型，属于多分子层化学吸附，是可正向自发进行的吸热过程。

Abstract:

      The sodium alginate （SA） hydrogel was successfully prepared by using SA as the substrate and ADH as the cross-linking agent at normal temperature and pressure. The chemical structure， surface morphology， thermal stability and swelling ability of SA hydrogel were characterized through Fourier transform infrared spectroscopy （FT-IR）， scanning electron microscope （SEM） thermogravimetry analysis （TG）， etc. And the adsorption performance and mechanism of the SA hydrogel towards heavy metal ions （Cu²⁺， Pb²⁺ and Cr⁶⁺） was investigated. The results showed that the SA was crosslinked through the amide bond （—CONH—） to form a hydrogel network， and the SA hydrogel with a “honeycomb” porous surface structure had good thermal stability and high swelling rate. Under the condition of adsorption temperature 25 ℃， initial mass concentration of heavy metal ions 50 mg/L， optimal adsorption pH value of adsorption system （pH=4 for Cu²⁺and Pb²⁺， pH=3 for Cr⁶⁺）， and the adsorption time 480 min， the SA hydrogel had good adsorption performance for Cu²⁺， Pb²⁺， and Cr⁶⁺， and the equilibrium adsorption capacity was 75.3， 129.5， and 26.4 mg/g， respectively. The dynamic and thermodynamic analysis showed that the adsorption process of SA hydrogel for Cu²⁺， Pb²⁺ and Cr⁶⁺ conformed to the pseudo second order kinetic model and Freundlich adsorption isotherm model， which belongs to the multi molecular layer chemical adsorption and was an endothermic process that can be carried out spontaneously in the forward direction.