Gelatin-bentonite composite as reusable adsorbent for the removal of lead from aqueous solutions: Kinetic and equilibrium studies

Gelatin-bentonite composite (GBC) gel were used as adsorbent for the removal of lead (II) from aqueous solutions. The developed adsorbents were characterized by XRD, FTIR, SEM, and EDX, analysis. The swelling and syneresis studies justified the reusability of GBC. Batch adsorption experiments systematically investigated the influence of contact time, metal ion concentration, adsorbent dosage, solution pH and regeneration of the adsorbent. The kinetic data fitted well with pseudo-first-order model and the equilibrium was reached within 4.0 h with 73.7% removal of lead (II) ions from aqueous solutions. The Langmuir, Freundlich and Temkin isotherm models were applied to describe equilibrium data. The adsorption isotherm followed Langmuir model with maximum adsorption capacity of 47.169 mg/g at 25 °C. The adsorption of lead (II) ions from aqueous solution was found to be pH dependent. The thermodynamic study confirmed that the adsorption was spontaneous and exothermic in nature. The regeneration of GBC with 0.1 (N) nitric acid was found excellent with ten adsorption-desorption cycles of reusability. Thus, GBC was found to be a superior adsorbent compared to other adsorbents due to its remarkable reusability after syneresis for lead (II) ions removal from aqueous solutions.