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

Abstract

© 2020 Elsevier Ltd 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.

Source or Periodical Title

Journal of Water Process Engineering

ISSN

22147144

Document Type

Article

Subject

Adsorption, Cesium removal, Covalent tethering, Macrocyclic ligand, Mesoporous silica

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