Adsorptive removal of nickel(II) ions from aqueous environments using gum based and clay based polyaniline/chitosan nanobiocomposite beads and microspheres: Equilibrium, kinetic, thermodynamics and ex-situ studies

The present study was carried out using gum (Ga) based and clay (MMT) based nanobiocomposite beads and microspheres composed of polyaniline NPs (PANI) and chitosan (Ch) as adsorbent for the removal of Ni(II) ions from aqueous environments. Under optimized conditions maximum Ni(II) removal 98.12% was exhibited by clay based nanobiocomposite (PANI-Ch-MMT) beads followed by gum based nanobiocomposite (PANI-Ch-Ga) beads (95.02%), PANI-Ch-MMT microspheres (85.12%) and PANI-Ch-Ga microspheres (75.23%). Equilibrium studies suggested a homogeneous mode of Ni(II) adsorption. Better applicability of pseudo-first order kinetic model suggested physisorption as the underlying phenomenon. Thermodynamic studies showed that adsorption was endothermic and spontaneous. The mechanism of adsorption by PANI-Ch-MMT and PANI-Ch-Ga beads was elucidated using SEM, EDX and FT-IR analyses. Ex-situ studies showed a maximum Ni(II) removal of 80.55% from mining wastewater using PANI-Ch-MMT beads in column mode. Regeneration studies suggested that PANI-Ch-MMT beads could be consistently reused up to five cycles.