Adsorption property and mechanism of vanadium(V) by supported bifunctionalized ionic liquid

Abstract

This study aims to investigate the adsorption behavior of supported bifunctionalized ionic liquids (SBILs) polystyrene [1-butyl-3-methylimidazolium][bis(2,4,4-trimethylpentyl)phosphinate] (PS[C4mim][C272]) for vanadium(V). PS[C4mim][C272] was synthesized through anion exchange using [PS][C4mim][Cl] and bis(2,4,4-trimethylpentyl) phosphine acid (Cyanex272) as precursors. The prepared SBILs were characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) to illustrate the successful loading of [C272]− onto SBILs. The results demonstrate that PS[C4mim][C272] adsorb V(V) by ionic conjugation. Under the preferred adsorption conditions, the equilibrium adsorption capacity of PS[C4mim][C272] reached 303.36 mg/g. The adsorption behavior of PS[C4mim][C272] for V(V) is more consistent with the Langmuir isotherm model, indicating that V(V) is adsorbed as monolayer. The adsorption process of PS[C4mim][C272] is consistent with the pseudo-second-order kinetic adsorption model, implying that the adsorption process is mainly chemical adsorption. Thermodynamics showed that the adsorption process of PS[C4mim][C272] was endothermic and spontaneous. The desorption of loaded V(V) and regeneration of PS[C4mim][C272] can be accomplished using 3 mol/L NH3·H2O solution one step. After 10 cycles, the adsorption capacity of PS[C4mim][C272] remains 96.58% of the initial value, implying the perfect adsorption stability of PS[C4mim][C272]. Meanwhile, PS[C4mim][C272] could effectively separate vanadium(V) from Fe(III) and Al(III) ions.