Electrochemically Selective Separation of Cesium Ion Using a Silicomolybdate Doped Polyaniline Composite

Rational design of efficient adsorbents for recovering Cs+ from complex brines is crucial for the sustainable industrial supply of cesium resources. Herein, a novel silicomolybdate doped polyaniline composite (SiMo12–PANI) was facilely prepared and used for extracting Cs+ via the electrochemical process for the first time. Silicomolybdic acid contains abundant oxygen sites and can be used as a receptor of Cs+. The morphology and chemical structure of the composite were fully characterized, and the effects of potential, ion concentration, and solution pH in the electrochemical separation Cs+ process were further studied. The results revealed that the SiMo12–PANI electrode exhibited a relatively fast ad/desorption kinetics of Cs+ due to the intensifying effect of the electric field. The adsorption capacity can be increased from 14.4 mg·g–1 to 24.9 mg·g–1 at the initial cesium concentration of 50 mg·L–1, and the desorption ratio was also improved. In particular, the separation factors of Cs+ over K+, Rb+, Ca2+, and Mg2+ can reach 11.7–16, 2.1–2.3, 205–726, and 622–708, respectively. XPS results confirmed that the excellent selectivity for Cs+ was achieved by ultra-affinity of oxygen donors toward Cs+, and the reversible capture and release of Cs+ may be achieved by the driving force of the electric field and the redox reaction between Mo6+ and Mo5+. It is expected that our work may provide a green and sustainable approach for selective recovery of Cs+ from complex solutions using a novel silicomolybdate doped polyaniline composite via an electrochemical process.