Development of Adsorption-Desorption Technique of Rare-Earth Metal Ions Using Phase Transition Behavior of Zwitterionic Polymer Brushes

Abstract

This study realized to develop a sulfobetaine-typed zwitterionic polymer brush on a porous silica particle (P-SiO2-poly(DMAPS)) through surface-initiated atom transfer radical polymerization (SI-ATRP), and demonstrate its applicability as an adsorption–desorption material for lanthanide (Ln) ions in aqueous solutions. Appropriate Ln adsorption conditions using P-SiO2-poly(DMAPS) were established, according to the effects of various metal ions on the thermos-responsive behaviors of poly(DMAPS) itself in aqueous solutions. From the adsorption experiments, it was confirmed that P-SiO2-poly(DMAPS) enabled the complete recovery of all Ln ions from aqueous solutions. The regression analyses to Langmuir adsorption isotherm curves of Ln ions at 50–70 °C showed that the chemisorption processes of all Ln ions on P-SiO2-poly(DMAPS) were entropy-driven and occurred spontaneously, while the maximum adsorption capacities of Ln ions decreased as the ionic radii decreased from light to heavy Ln. Furthermore, 100 % of all Ln ions adsorbed on P-SiO2-poly(DMAPS) were allowed to desorb by simple shaking in a certain concentration of ethylenediaminetetraacetic acid (EDTA) solution. These results prove that a novel Ln adsorption–desorption technique using a zwitterionic polymer brush has great potential in chemical, environmental, and energy fields.