Acta Chim Slov. 2021 Sep;68(3):548-561.
The adsorption of manganese ions from aqueous solutions by pure and acid-treated Opuntia ficus indica as natural low-cost and eco-friendly adsorbents was investigated. The adsorbents' structures were characterized by powder X-ray diffraction and infrared spectroscopy. Specific surface areas were determined using the Brunauer-Emmett-Tell equation. The study was carried out under various parameters influencing the manganese removal efficiency such as pH, temperature, contact time, adsorbent dose and initial concentration of manganese ion. The maximum adsorption capacity reached 42.02 mg/g for acid-treated Opuntia ficus indica, and only 20.8 mg /g for pure Opuntia ficus indica. The Langmuir, Freundlich and Temkin isotherms equations were tested, and the best fit was obtained by the Langmuir model for both adsorbents. The thermodynamic study shows that chemisorption is the main adsorption mechanism for the activated adsorbent while physisorption is the main adsorption mechanism for the pure adsorbent. The kinetics of the adsorption have been studied using four kinetics models of pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion. Structural analyses indicate the appearance of MnOx oxides on the cellulose fibers. The adsorption mechanisms consist of an electrostatic interaction followed by oxidation of the Mn (II) to higher degrees, then probably by binding to the surface of the adsorbent by different C-O-MnOx bonds.
研究了用纯仙人掌和酸处理的仙人掌作为天然、低成本和环保吸附剂从水溶液中吸附锰离子。通过粉末 X 射线衍射和红外光谱对吸附剂的结构进行了表征。比表面积采用 Brunauer-Emmett-Tell 方程确定。研究了影响锰去除效率的各种参数，如 pH 值、温度、接触时间、吸附剂剂量和锰离子初始浓度。酸处理的仙人掌的最大吸附容量达到 42.02mg/g，而纯仙人掌的最大吸附容量仅为 20.8mg/g。对 Langmuir、Freundlich 和 Temkin 等温线方程进行了测试，两种吸附剂都通过 Langmuir 模型得到了最佳拟合。热力学研究表明，对于活化吸附剂，化学吸附是主要的吸附机制，而对于纯吸附剂，物理吸附是主要的吸附机制。通过准一级、准二级、Elovich 和内扩散动力学模型研究了吸附动力学。结构分析表明，在纤维素纤维上出现了 MnOx 氧化物。吸附机制包括静电相互作用，随后 Mn(II)被氧化到更高程度，然后可能通过不同的 C-O-MnOx 键与吸附剂表面结合。
