Sequestration of heavy metal ions by Methionine modified bentonite/Alginate (Meth-bent/Alg): A bionanocomposite

• Removal of Pb(II)-(98%) and Cd(II)-(82%).
• Freundlich model.
• Desorption using oxalic acid.

The present work critically evaluated the role of (Meth-bent/Alg) nanocomposite as an adsorbent for the removal of Pb(II) and Cd(II). The synthesized adsorbent was characterized by SEM, TEM, EDX, XRD, TGA–DTA and FTIR. The equilibrium was attained in 120 min and the optimum pH for adsorption was found 5 and 4 for Pb(II) and Cd(II) respectively. The experimental data is better fitted to pseudo second order kinetics and Freundlich isotherm model with lower value of root mean square error. The adsorption capacities for Pb(II) and Cd(II) obtained from Langmuir isotherm was 30.86 and 217.39 mg g−1 at 303 K. The thermodynamic parameter shows the process to be exothermic, spontaneous with increased randomness of the adsorbent. The desorption study shows that 99% of the adsorbed Pb(II) and Cd(II) can be desorbed by using 0.1 M oxalic acid as eluting agent with regeneration capability upto fifth cycle successfully.

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