Removal of Cs+ in water by dibenzo-18-crown-6 ether tethered on mesoporous SBA-15 as a reusable and efficient adsorbent

[Display omitted] •Cs+ adsorbent was prepared by covalent tethering of DB18C6 ligand on SBA-15.•DB16C6-SBA exhibits high Cs+ capacity (94.54 mg g−1) from Hill isotherm model.•Cs+ uptake is spontaneous, endothermic, and follows pseudo-second order rate model.•DB16C6-SBA is Cs+-selective with competitive KD and CF for contaminated water treatment.•It can be repeatedly used with consistent performance in adsorption-nanofiltration system. Inadvertent release of radioactive Cs+ to the environment poses a grave threat as it may cause severe health problems to the exposed population. One of the practical solutions is to use effective regenerable Cs+ adsorbents to minimize total waste volume. In this study, a mesoporous adsorbent for Cs+ capture was prepared by tethering a Cs+-selective ligand monoamino-dibenzo-18-crown-6 (MA-DB18C6) ether on chloro-functionalized SBA-15 (Cl-SBA) support. The dispersible adsorbent (DB18C6-SBA) registered a maximum adsorption capacity of 94.54 mg g−1 from non-linear Hill isotherm fitting. The model suggests near Langmuir-type of Cs+ capture as Hill coefficient nH→1. This indicates nearly independent monolayer Cs+ binding with the tethered DB18C6 with no adsorbate interaction. Kinetic study reveals a pseudo-second order of Cs+ uptake rate while thermodynamic analyses show the spontaneity and endothermicity of the process. Compared with conventional ligand impregnation technique, covalently tethered DB18C6 occupy smaller surface space of SBA-15 resulting in higher ligand loading and higher adsorption capacity. DB18C6-SBA is regenerable in mild acid and exhibits consistent adsorption capacity after several reuse cycles. It can selectively capture Cs+ from simulated high level liquid waste, but more effectively from Cs+-contaminated surface water with KD ∼ 1578 mL g−1 and concentration factor CF ∼ 2267 in the presence of Na+, K+, Mg2+ and Ca2+. Cycled batch adsorption shows that DB18C6-SBA can be reused with consistent uptake performance while lab-scale sequential adsorption-nanofiltration system with Cs+ stripping further demonstrates its potential long-term use as Cs+ adsorbent for the treatment of contaminated water.