School of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, China.
Huizhou Research Institute of Sun Yat-sen University, Huizhou 516216, China.
Molecules. 2019 Nov 20;24(23):4205. doi: 10.3390/molecules24234205.
Gel adsorption is an efficient method for the removal of metal ion. In the present study, a functional chitosan gel material (FCG) was synthesized successfully, and its structure was detected by different physicochemical techniques. The as-prepared FCG was stable in acid and alkaline media. The as-prepared material showed excellent adsorption properties for the capture of Cu ion from aqueous solution. The maximum adsorption capacity for the FCG was 76.4 mg/g for Cu ion (293 K). The kinetic adsorption data fits the Langmuir isotherm, and experimental isotherm data follows the pseudo-second-order kinetic model well, suggesting that it is a monolayer and the rate-limiting step is the physical adsorption. The separation factor (R) for Langmuir and the value for Freundlich isotherm show that the Cu ion is favorably adsorbed by FCG. The negative values of enthalpy (ΔH°) and Gibbs free energy (ΔG°) indicate that the adsorption process are exothermic and spontaneous in nature. Fourier transform infrared (FTIR) spectroscopy and x-ray photoelectron spectroscopy (XPS) analysis of FCG before and after adsorption further reveal that the mechanism of Cu ion adsorption. Further desorption and reuse experiments show that FCG still retains 96% of the original adsorption following the fifth adsorption-desorption cycle. All these results indicate that FCG is a promising recyclable adsorbent for the removal of Cu ion from aqueous solution.
凝胶吸附是去除金属离子的一种有效方法。本研究成功合成了一种功能性壳聚糖凝胶材料（FCG），并通过不同的物理化学技术对其结构进行了检测。所制备的 FCG 在酸碱性介质中稳定。所制备的材料对水溶液中 Cu 离子的捕获表现出优异的吸附性能。FCG 对 Cu 离子的最大吸附容量为 76.4 mg/g（293 K）。动力学吸附数据符合 Langmuir 等温线，实验等温线数据很好地遵循伪二阶动力学模型，表明这是一个单层，限速步骤是物理吸附。Langmuir 的分离因子（R）和 Freundlich 等温线的 值表明，FCG 对 Cu 离子的吸附是有利的。焓变（ΔH°）和吉布斯自由能变（ΔG°）的负值表明吸附过程是放热和自发的。吸附前后 FCG 的傅里叶变换红外（FTIR）光谱和 X 射线光电子能谱（XPS）分析进一步揭示了 Cu 离子吸附的机理。进一步的解吸和重复使用实验表明，FCG 在第五次吸附-解吸循环后仍保留 96%的原始吸附量。所有这些结果表明，FCG 是一种很有前途的可回收吸附剂，可用于从水溶液中去除 Cu 离子。
