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

摘要

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/KNiFe(CN)(6), denoted as PVA/GO/KNiFe(CN)(6)) was designed by a synergistic cross-linking reaction coupled with in situ precipitation strategy. PVA and Ni2+ firstly played synergistic roles in reinforcement of interwoven structure, and Ni2+ coordinated with Fe(CN)(6)(3-) to produce KNiFe(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.