Abstract

A novel lanthanum-sodium alginate hydrogel (La-SA) biosorbent has been successfully prepared by the cross-linking reaction of sodium alginate (SA) with lanthanum(III) ions, and characterized by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), Fourier Transform-Infrared (FTIR), UV visible diffuse reflectance spectroscopy (UV-Vis DRS), Thermogravimetric Analysis (TGA) and determination of point of zero charge (pHpzc), respectively. The adsorption experiments revealed that La-SA gel beads showed the excellent adsorption performance for the removal of anionic azo-dyes Direct Green 1 (DG 1) and Acid Blue 113 (AB 113) from aqueous solution at pH < 6.0, while the high-efficiency adsorption of DG could allow in a wider pH range of 2.0 ∼ 10.0. Langmuir and Freundlich models were used for dealing with the equilibrium data and it is found that the adsorption behaviors of DG 1 and AB 113 onto La-SA are perfectly in accordance with the Langmuir model, and the corresponding maximum adsorption capacities can reach 909 and 983 mg/g at 40 °C, respectively. The kinetics adsorption data fully conformed to the pseudo-second-order rate equation, and adsorption processes were mainly controlled by intraparticle diffusion. The thermodynamic studies and spectral characterization indicate the adsorption reactions of two dyes are of spontaneous and endothermic nature, and strongly depend on the the electrostatic interaction, hydrogen bonding and ligand exchange between dye anions and La-SA gel beads. La-SA biosorbent with low cost and high efficiency would have a good application prospect in the purification of high-concentration dye wastewater.

摘要

通过海藻酸钠（SA）与镧（III）离子的交联反应，成功制备了一种新型的海藻酸钠镧水凝胶（La-SA）生物吸附剂，并通过扫描电子显微镜（SEM）和能量色散谱表征。 EDS)、X 射线衍射 (XRD)、傅里叶变换红外 (FTIR)、紫外可见漫反射光谱 (UV-Vis DRS)、热重分析 (TGA) 和零电荷点测定 (pHpzc)。吸附实验表明，La-SA 凝胶珠在从 pH < 6.0 的水溶液中去除阴离子偶氮染料 Direct Green 1 (DG 1) 和 Acid Blue 113 (AB 113) 方面表现出优异的吸附性能，而高- DG 的高效吸附可以允许在 2.0 ∼ 10.0 的更宽 pH 范围内。用Langmuir和Freundlich模型处理平衡数据，发现DG 1和AB 113在La-SA上的吸附行为完全符合Langmuir模型，对应的最大吸附容量可达909和983分别为 40 °C 时的 mg/g。动力学吸附数据完全符合拟二级速率方程，吸附过程主要受颗粒内扩散控制。热力学研究和光谱表征表明两种染料的吸附反应具有自发性和吸热性，强烈依赖于染料阴离子和 La-SA 凝胶珠之间的静电相互作用、氢键和配体交换。