Selective recovery of cesium and cobalt ions using an inorganic ion exchanger: Batch, column studies, and cementitious immobilization

Abstract

Radionuclides such as Co2+ and Cs+ are commonly present in liquid effluents generated from nuclear facilities, and their efficient removal is essential for minimizing environmental contamination and radiation hazards. In this study, a barium zirconium phosphate (BZP) inorganic sorbent with good thermal stability and high affinity toward metal ions was synthesized by the co-precipitation method and evaluated for the selective recovery of Cs(I) and Co(II) ions from aqueous solutions. The synthesized material was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM – EDX), X-ray diffraction (XRD), and thermal analyses (DTA/TGA). The effects of solution pH on the removal efficiency and distribution coefficient (Kd) were investigated, revealing a higher selectivity toward Co(II) than Cs(I). Maximum removal % of 65.1% and 95.2% were achieved at pH 4 for Cs(I) and Co(II), respectively. Thermodynamic studies indicated that the adsorption process was spontaneous, endothermic, and predominantly governed by physical adsorption. The saturation capacities of the BZP sorbent were found to be 15.5 mg g−1 for Cs(I) and 29.5 mg g−1 for Co(II). The saturation capacity and thermal stability studies demonstrated that the sorbent retained a reasonable adsorption performance up to 500°C. Fixed-bed column experiments demonstrated breakthrough capacities of 12.8 and 24.0 mg g−1 for Cs(I) and Co(II), respectively, confirming the sorbent’s applicability under dynamic operating conditions. The BZP sorbent was successfully immobilized in a cementitious matrix, with an optimum loading of (5 wt.%), resulting in an enhancement in the compressive strength and the effective capillary porosity, by approximately 4.6%, 1% respectively, with an enhancement in overall mechanical performance. These findings demonstrate that BZP is a promising inorganic material for the selective removal and immobilization of radionuclides from aqueous waste streams, offering potential applications in radioactive waste treatment and long-term disposal.