Adsorption application of Rb+ on hydrogels of hydroxypropyl cellulose/polyvinyl alcohol/reduced graphene oxide encapsulating potassium cobalt hexacyanoferrate

Abstract

Specific ion exchangers/adsorbents are used to separate low concentration rubidium (Rb) resources from seawater or salt lakes, especially potassium cobalt hexacyanoferrate (KCoFC) with high adsorption capacity and selectivity for Rb+. However, there are great challenges in recovery from solution for powder form KCoFC. Herein, a new immobilization strategy was presented, and KCoFC was encapsulated by synthetic hydrogels of hydroxypropyl cellulose/polyvinyl alcohol/reduced graphene oxide (KCoFC‐HPR). Scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy were employed to indicate the correct encapsulation of KCoFC. The adsorption behavior of KCoFC‐HPR for Rb+ was investigated, and the results demonstrated that the process conformed to pseudo‐second‐order kinetic model and Langmuir isotherm model with the exchange of Rb+ and K+ as main adsorption mechanism. The maximum adsorption capacity for Rb+ on KCoFC‐HPR achieved 211.2 mg g−1 at 25°C. The interference of lithium and sodium ions (Li+/Na+:Rb+ = 20:1) on the adsorption capacity proved negligible. Within 24 h, 77.9% of adsorbed Rb+ on KCoFC‐HPR in 0.5 mol L−1 NH4Cl/HCl mixture was desorbed, and adsorption capacity for the regenerated sample was 88.1% of the initial sample.