Fast and effective sorption of radioactive Sr(II) onto mesoporous silicate

Abstract

A mesoporous silicate material (MS) was effectively synthesized and applied as a solid sorbent for removal of radioactive Sr(II) ions from aqueous solution. MS was characterized using different tools including N2 adsorption-desorption analysis, FT-IR, XRD and SEM. The synthesized material has crystalline, porous nature and exhibited a large surface area of about 905.18 m2 g−1. The uptake of Sr(II) ions onto MS was investigated under different batch experimental conditions involving pH, equilibrium time, sample weight and initial concentration of Sr(II) ions. About 98 % of Sr(II) radionuclides were uptaken at pH 12 in the first minute. Different isotherm models (Langmuir, Freundlich, Dubinin-Radushkevich and Temkin) were applied to analyze the obtained experimental sorption equilibrium data. The Langmuir isotherm model was aligned well with the sorption data. The maximum sorption capacity (Q max) of MS towards strontium ions attained the value 0.991 mmol/g. The parameters (ΔG°, ΔH° and ΔS°) were calculated from thermodynamic study and their values showed that sorption process of Sr(II) ions on MS is strong, take place spontaneously, and considered as endothermic process. The synthesized MS had the ability to efficiently remove Sr(II) radionuclides even in the presence of Na+ and Ca2+ as competing cations in aqueous solution. Among the studied desorbing agents, CaCl2 was the best one for desorbing Sr(II) radionuclides loaded onto MS. The synthesized MS was reused for sorption of strontium up to four cycles with acceptable efficiency.

Comparative Study on the Proton Conduction Behaviors of Two Acidic Amphiphilic and Hydrophilic Coordination Compounds in Nafion Composite Membranes

“…The water absorption of H 4 (Co-L1) and H­(Ni-L2) at 25 °C was simulated using the Monte Carlo (GCMC) method. The sorption module in the Material Studio software package was utilized to calculate van der Waals forces and electrostatic interactions with the SQUEEZE command based on atom, Ewald and Group methods . As depicted in Figure S2, each unit cell of H 4 (Co-L1) can absorb three water molecules, equivalent to 0.0156 g of water per gram of H 4 (Co-L1); while each unit cell of H­(Ni-L2) can absorb four water molecules, equivalent to 0.0398 g of water per gram of H­(Ni-L2).…”

“…The sorption module in the Material Studio software package was utilized to calculate van der Waals forces and electrostatic interactions with the SQUEEZE command based on atom, Ewald and Group methods. 43 As depicted in Figure S2, each unit cell of H 4 (Co-L1) can absorb three water molecules, equivalent to 0.0156 g of water per gram of H 4 (Co-L1); while each unit cell of H(Ni-L2) can absorb four water molecules, equivalent to 0.0398 g of water per gram of H(Ni-L2). Clearly, the water absorption capacity of H(Ni-L2) is significantly stronger than that of H 4 (Co-L1), which can be attributed to the hydrophobic nature of phen ligand hindering its water absorption, whereas the abundant coordination water molecules and uncoordinated carboxylate groups in H(Ni-L2) facilitate its uptake of water molecules.…”