Department of Applied Chemistry, Saga University, Honjo 1, Saga 840-8502, Japan.
J Hazard Mater. 2011 Aug 30;192(2):676-82. doi: 10.1016/j.jhazmat.2011.05.070. Epub 2011 May 27.
Adsorption gels for fluoride ion were prepared from orange waste by saponification followed by metal loading. The pectin compounds contained in orange waste creates ligand exchange sites once it is loaded with multi-valent metal ions such as Al(3+), La(3+), Ce(3+), Ti(4+), Sn(4+), and V(4+) to be used for fluoride removal from aqueous solution. The optimum pH for fluoride removal depends on the type of loaded metal ions. The isotherm experiments showed the Langmuir type monolayer adsorption. Among all kinds of metal loaded gels tested, Al loaded gel appeared to exhibit the most favorable adsorption behavior. The adsorption kinetics of fluoride on loaded gel demonstrated fast adsorption process. The presence of NO(3)(-), Cl(-) and Na(+) ions has negligible effect on fluoride removal whereas SO(4)(2-) and HCO(3)(-) retarded the fluoride removal capacity in some extent. Fluoride removal at different adsorbent doses showed that fluoride concentration can be successfully lowered down to the acceptable level of environmental standard. The fluoride adsorption mechanism was interpreted in terms of ligand exchange mechanism. The complete elution of adsorbed fluoride from the gel was successfully achieved using NaOH solution.
从橙皮废弃物中通过皂化反应和金属负载制备了用于氟离子吸附的凝胶。橙皮废弃物中含有的果胶化合物在负载多价金属离子（如 Al(3+)、La(3+)、Ce(3+)、Ti(4+)、Sn(4+)和 V(4+)）后形成配体交换位点，可用于从水溶液中去除氟化物。从水溶液中去除氟化物的最佳 pH 值取决于负载金属离子的类型。等温线实验表明其符合 Langmuir 单层吸附模型。在所测试的各种负载凝胶中，负载 Al 的凝胶表现出最有利的吸附行为。负载凝胶对氟化物的吸附动力学表明其具有快速的吸附过程。NO(3)(-)、Cl(-)和 Na(+)离子的存在对氟化物的去除几乎没有影响，而 SO(4)(2-)和 HCO(3)(-)在一定程度上会降低氟化物的去除能力。在不同吸附剂剂量下进行的氟化物去除实验表明，氟化物浓度可以成功降低到环境标准的可接受水平。氟化物的吸附机制可以用配体交换机制来解释。使用 NaOH 溶液成功地从凝胶中完全洗脱了吸附的氟化物。
