A Comparative Study on the Rare Earth Elements Recovery of Cross-linked Cellulose Adsorbents and Capacitive Deionization with Cellulose Derived Carbon as Electrode Materials

摘要

The increasing demand for Rare Earth Elementals (REEs) due to their exponential use in various applications has stimulated research on the development of an efficient technology for the separation and recovery of REEs. Adsorption is one of the best and most typical methods, while capacitive deionization (CDI) is increasingly being considered as a promising solution for desalination and ions recovery. Cellulose, the most abundant and low-cost polysaccharides in the nature, has attracted great attention for its potential applications in adsorbent and energy storage fields, due to its excellent mechanical, abundant -OH functional groups, as well as the outstanding electronic and thermal properties after carbonization. With an objective to develop a cost-efficient and exceptional CDI electrode material with high specific surface area, low electrical resistance and durability, in this work, we developed a novel cellulose derived carbon electrode, and it was further applied for REEs recovery. The material exhibits the above-mentioned characteristics along with superior adsorption capability. As a comparison, a cellulose adsorbent was synthesized by crosslinking cellulose nanocrystal (CNC) with polyethylenimine (PEI). The adsorbent and electrode materials were characterized by Fourier Transform Infrared (FT-IR) spectroscopy, elemental analysis, Brunauer-Emmett-Teller (BET) analysis, Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM). The electrochemical capacitive behavior of the electrode material was determined by cyclic voltammetry (CV). Their adsorption behaviors of the cellulose adsorbent for the removal of REEs by varying experimental conditions were investigated in bath. The CDI recovery performance was also studied using a laboratory CDI module, under varying voltage and REE concentrations. The REEs uptake ability, and the kinetics and isotherms of the both methods for REEs uptake were further compared. The REEs uptake mechanisms of the both methods were studied via FTIR and XPS as well.Such a comparison is not only useful for further understanding the fundamental of the traditional adsorption and electrosorption, but also for promoting the CDI application in water treatment.