Encapsulation of ammonium molybdophosphate and zirconium phosphate in alginate matrix for the sorption of rubidium(I).

Ammonium molybdophosphate and Phozir (alone or in combination) have been encapsulated in alginate beads for the synthesis of rubidium sorbents. SEM and SEM-EDX analyses confirm the homogeneity of the sorbents in terms of composition and metal binding. AMP sorbent is less sensitive to pH than Phozir, and optimum pH is close to pH 3 for the binding of Rb(I). The Langmuir equation fitted well sorption isotherms and the maximum sorption capacities were in the range 0.65-0.74 mmol Rb g(-1). The resistance to intraparticle diffusion contributes to control uptake kinetics (effect of particle size) though the presence of solid inorganic particles reduces the impact of drying alginate capsules (preventing the collapse of the porous structure during the drying step). Breakthrough curves demonstrate the potential of these sorbents for the dynamic sorption of Rb(I) while using ammonium chloride (combined to nitric acid) allows recovering Rb(I) from loaded sorbents.