Effective retention of radioactive Cs+ and Ba2+ ions using β-cyclodextrin functionalized diatomite (β-CD/D) as environmental adsorbent; characterization, application, and safety

Abstract

The siliceous frustules of diatomite were integrated with β-cyclodextrin polymer in novel composite (β-CD/D) for enhanced retention properties for radioactive ions. The β-CD/D composite was characterized by different analytical techniques and applied in batch adsorption studies for the dissolved Cs+ and Ba2+ ions. The β-CD/D composite exhibits promising retention capacities (Cs+ (144.5 mg/g) and Ba2+ (195.7 mg/g)) which are higher than its components and other evaluated adsorbent in literature. The Cs+ and Ba2+ retention reactions by β-CD/D are of Langmuir properties, Pseudo-Second order kinetics, and Gaussian energies less than 8 KJ/mol. Therefore, the ions were adsorbed homogeneously in monolayer forms by physicochemical mechanisms involved in electrostatic attraction and the formation of chemical complexes. The thermodynamic parameters suggested spontaneous and exothermic behaviors for the occurred Cs+ and Ba2+ retention reactions. The synthetic β-CD/D is of significant affinities for the Cs+ and Ba2+ ions in the presence of competitive anions (HCO3−, SO42−, NO3−, and PO43−) and considerable affinitive in the presence of other metals (Cd2+, Pb2+, Zn2+, and Co2+). The β-CD/D composite also is a highly recyclable product and can be reused effectively in Cs+ and Ba2+ removal processes for five cycles.