Hexacyanoferrate-modified polyvinyl alcohol/graphene oxide aerogel as an efficient and retrievable adsorbent for cesium

While hexacyanoferrate and its analogues are specific adsorbents for elimination of cesium ions (Cs + ), they seem to encounter a major challenge of separation from solution. To solve this difficulty, a novel aerogel adsorbent (polyvinyl alcohol/graphene oxide/KNi[Fe(CN) 6 ], denoted as PVA/GO/KNi[Fe(CN) 6 ]) was designed by a synergistic cross-linking reaction coupled with in situ precipitation strategy. PVA and Ni 2+ firstly played synergistic roles in reinforcement of interwoven structure, and Ni 2+ coordinated with [Fe(CN) 6 ] 3− to produce KNi[Fe(CN) 6 ] in situ in the following step. Characterization analysis revealed a hierarchical structure of the aerogel composed of GO sheets and nanoparticles. This unique structure enhanced adsorption performance compared with PVA/GO. Results indicated that pseudo-second-order model ( R 2  = 0.9971) and intraparticle diffusion model ( R 2  = 1.000, 0.9959 and 0.8513) fitted the kinetic data well, suggesting that the rate-limiting step was governed by the chemisorption and diffusion mechanism. Isotherm data were better described by the Langmuir model ( R 2  = 0.9970), indicating monolayer homogeneous adsorption. The structural investigation verified that the substitution of Cs + for K + (lattice) or for H + (carboxyl groups) was the possible adsorption mechanism. The as-prepared adsorbent exhibited satisfactory adsorption capacity of 47.66 mg/g and a merit of easy separation (as a monolith aerogel) and may be taken as a potential candidate for Cs + cleanup. Graphical abstract