Evaluation of silica/ferrocyanide composite as a dual-function material for simultaneous removal of ¹³⁷Cs⁺ and ⁹⁹TcO₄⁻ from aqueous solutions

A novel mesoporous silica-coated ferrocyanide (MSCFC) composite was successfully synthesized and evaluated as a dual-function material for simultaneous removal of ¹³⁷Cs⁺ cations and ⁹⁹TcO₄⁻ anions from aqueous solutions. Sorption behavior of both radionuclides on MSCFC under different experimental conditions has been studied using a batch technique. Results revealed that about 100% of ¹³⁷Cs⁺ and 97% of ⁹⁹TcO₄⁻ were removed by MSCFC in the pH ranges of 2.2–12.4 and 4.1–9.5, respectively. Sorption kinetic data were analyzed by pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models, while Langmuir and Freundlich models were applied for the sorption isotherms. The maximum sorption capacity of MSCFC for radiocesium was determined and compared with other reported sorbents. Applicability of the coated ferrocyanide for simultaneous removal of ¹³⁷Cs⁺ and ⁹⁹TcO₄⁻ from low-level liquid radioactive waste (LLLW) was also tested, and the data revealed that 99.91% and 98.34% were removed from ¹³⁷Cs⁺ and ⁹⁹TcO₄⁻, respectively. It is concluded that MSCFC exhibits excellent efficiency for simultaneous removal of the mixed radionuclides with different charge from LLLW. - Highlights: • MSCFC was synthesized and applied for simultaneous removal of ¹³⁷Cs⁺ and ⁹⁹TcO₄⁻. • ¹³⁷Cs⁺ and ⁹⁹TcO₄⁻ were effectively removed through wide pH ranges. • A high Q_max (231.3 mg g⁻¹) was obtained for radiocesium by MSCFC. • ¹³⁷Cs⁺ and ⁹⁹TcO₄⁻ were successfully removed simultaneously from LLLW using MSCFC