Adsorption of mercury(II) ions on Procion Blue MX-3G-attached magnetic poly(vinyl alcohol) gel beads

Magnetic poly(vinyl alcohol) (mPVAL) gel beads (150-200 μm in diameter) carrying Procion Blue MX-3G (122 μmol/g) were used for the removal of different amounts (50-650 mg/1) of Hg (II) ions from aqueous solutions. The mPVAL gel beads were characterized by swelling tests, electron spin resonance (ESR), elemental analysis and scanning electron microscopy (SEM). The swelling ratio of the mPVAL gel beads, which had a spherical shape and porous structure, was 76%. The presence of magnetic particles in the polymeric structure was confirmed by ESR spectroscopy. The capacity of the beads towards Hg(II) ions increased with time during the first 10 min of adsorption and then levelled off towards an equilibrium adsorption capacity. The adsorption of Hg(II) ions on the plain beads was very low (0.57 mg/g) but increased substantially (to 69.2 mg/g) on beads to which Procion Blue MX-3G had been attached. The Langmuir adsorption isotherm was applicable to the description of Hg(II) ion adsorption by Procion Blue MX-3G-attached mPVAL gel beads. Such adsorption increased with increasing pH of the aqueous medium and reached a plateau level at ca. pH 6.0. The optimal pH range for Hg(II) ion adsorption was 6.0-7.0. More than 95% of the adsorbed Hg(II) ions was desorbed within 15 min when 0.1 M HNO₃ was used as an elution agent. Regeneration of the Procion Blue MX-3G-attached mPVAL gel beads under these conditions was also reasonable.