Application of Gum Based and Clay Based CuO/Chitosan Nanobiocomposite Beads for the Removal of Nickel(II) from Aqueous Environments:Equilibrium, Kinetic, Thermodynamic and ex-Situ Studies

The present investigation is focused on the removal of Ni(II) ions from aqueous environment using gum (GA) based and clay (MMT) based nanobiocomposite beads composed of CuO NPs and chitosan (Ch). The potential of beads was exploited in terms of pH (2.0-10.0), contact time (2-36 h), temperature (10-50 °C), initial metal concentration (100-1200 mg L^-1) and adsorbent dosage (1.0-6.0 g L^-1) during the adsorption process. Under optimized condition, maximum Ni(II) removal (95.05%) was exhibited by clay based nanobiocomposite (CuO-Ch-MMT) beads followed by gum based nanobiocomposite (CuO-Ch-GA) beads (90.12%). Equilibrium data showed the best fit to Langmuir model with the highest adsorption capacity suggesting a homogeneous mode of Ni(II) adsorption onto the nanobiocomposite beads. Kinetic studies showed better applicability of pseudo-first order model suggesting physisorption as the underlying phenomena. Thermodynamic studies showed that the process was endothermic and spontaneous. The adsorption mechanism of CuO-Ch-GA and CuO-Ch-MMT beads was further elucidated using SEM, EDX and FT-IR analyses. Ex-situ studies showed a maximum Ni(II) removal of 88.26% from electroplating wastewater using CuO-Ch-MMT beads in column mode. Regeneration studies suggested that CuO-Ch-MMT beads could be consistently reused up to 4 cycles.