Recovery of cesium ions from seawater using a porous silica-based ionic liquid impregnated adsorbent

A porous silica-based adsorbent was prepared by impregnating the pores of a silica support with the extractant 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-calix[4]arene (Calix[4]arene-R14) and an additive agent 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C 2 mim  +  NTf 2 − ) as the materials to remove cesium(I) (Cs + ) ions from seawater. The as-prepared adsorbent showed excellent adsorption performance toward Cs + ions, with adsorption equilibrium reached within 2 h and an adsorption amount of 0.196 mmol/g observed. The solution pH, temperature, and the presence of coexisting metal ions were found to have almost no effect on Cs + adsorption. The adsorption mechanism was considered to proceed via ion exchange between Cs + and C 2 mim + . In addition, the particle-induced X-ray emission analysis results further clarified that the adsorbed Cs + ion species on the adsorbent was in the form of both CsCl and CsBr.