Universitat Politècnica de Catalunya, Department of Chemical Engineering, ETSEIB, Diagonal 647, 08028, Barcelona, Spain; Universidad Técnica de Machala, School of Chemical Engineering, FCQS, BIOeng Research Group, 070151, Machala, Ecuador.
Universitat Politècnica de Catalunya, Department of Chemical Engineering, ETSEIB, Diagonal 647, 08028, Barcelona, Spain.
Environ Pollut. 2020 Sep;264:114409. doi: 10.1016/j.envpol.2020.114409. Epub 2020 Apr 29.
Rare earth elements (REE) present multiple applications in technological devices but also drawbacks (scarcity and water contaminant). The current study aims to valorise the banana wastes - banana rachis (BR), banana pseudo-stem (BPS) and banana peel (BP) as sustainable adsorbent materials for the recovery of REE (Nd, Eu, Y, Dy and Tb). The adsorbent materials were characterized using analytical techniques such as: Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, zeta potential and scanning electron microscopy with energy dispersive X-ray probe. The adsorption performance and mechanisms were studied by pH dependence, equilibrium isotherms, kinetics, thermodynamics, ion-exchange and desorption evaluation. The results show good adsorption capacities for the three materials, highlighting BR that presents ∼100 mg/g for most of the REE. The adsorption process (100 mg REE/L) reaches the 60% uptake in 8 min and the equilibrium within 50 min. On the other hand, the thermodynamic study indicates that the adsorption is spontaneous and exothermic (ΔH° < 40 kJ/mol). The adsorption mechanism is based on the presence of carboxylic groups that induce electrostatic interactions and facilitate the surface nucleation of REE microcrystals coupled to an ion exchange process as well as the presence of other oxygen containing groups that establish weak intermolecular forces. The recovery of REE from the adsorbent (∼97%) is achieved using EDTA as desorbing solution. This research indicates that banana waste and particularly BR is a new and promising renewable bioresource to recover REE with high adsorption capacity and moderated processing cost.
稀土元素（REE）在技术设备中有多种应用，但也存在一些缺点（稀缺性和水污染）。本研究旨在将香蕉废弃物——香蕉穗轴（BR）、香蕉假茎（BPS）和香蕉皮（BP）作为可持续的吸附材料，用于回收 REE（Nd、Eu、Y、Dy 和 Tb）。采用傅里叶变换红外光谱、X 射线光电子能谱、Zeta 电位和带有能量色散 X 射线探头的扫描电子显微镜等分析技术对吸附剂材料进行了表征。通过 pH 值依赖性、平衡等温线、动力学、热力学、离子交换和洗脱评价研究了吸附性能和机制。结果表明，三种材料对 REE 都具有良好的吸附能力，BR 对大多数 REE 的吸附量高达 100mg/g。吸附过程（100mgREE/L）在 8 分钟内达到 60%的吸收量，50 分钟内达到平衡。另一方面，热力学研究表明，吸附是自发的和放热的（ΔH°<40kJ/mol）。吸附机制基于存在羧酸基团，诱导静电相互作用，并促进 REE 微晶的表面成核，同时存在其他含氧基团，建立弱分子间力。通过使用 EDTA 作为洗脱液，可以从吸附剂中回收 REE（约 97%）。本研究表明，香蕉废弃物，特别是 BR，是一种新的、有前途的可再生生物资源，可用于回收具有高吸附能力和适中处理成本的 REE。
