Development and application of a new macrocyclic ligand-functionalized mesoporous silica sorbent for selective separation of radiocesium from environmental wastewater

Abstract

The growing reliance on nuclear energy and uncharacteristic accidents, such as those in Chornobyl and Fukushima, have emphasized the need for effective radiocesium (r-Cs: 137Cs) removal from environmental wastewater. This study presents the development of DFDB18C6@SBA-NH2, a novel solid-phase sorbent designed to remove r-Cs from aqueous environments selectively. The sorbent was synthesized by tethering a macrocyclic ligand, DFDB18C6 (di-formyl dibenzo-18-crown-6-ether), to amino-functionalized mesoporous SBA-15 (Santa Barbara Amorphous-15). The sorbent’s structure, thermal properties, and surface morphology were comprehensively characterized. Batch sorption experiments were performed to evaluate the influence of different operating factors on r-Cs sorption, including solution pH, contact duration, initial ion concentration, ambient temperature, and matrix ions contents. The sorption behavior was better explained with the pseudo-second-order kinetic and Langmuir isotherm models, which suggest a probable monolayer chemisorption process. The thermodynamic evaluation indicated the exothermic nature of the sorption process. The DFDB18C6@SBA-NH2 sorbent demonstrated significant 137Cs removal (approximately 85 %) from Fukushima-originated wastewater, with competing matrix ions such as Ca2+, Mg2+, Na+, and K+. These results highlight the potential of DFDB18C6@SBA-NH2 as a potential solid-phase sorbent for efficient and selective r-Cs decontamination in waste aqueous matrices.