Effective removal of Cd(II), Pb(II) and Cr(VI) from aqueous solution using Bauhinia variegata leaves after chemical modifications

This study deals with biosorption of Pb(II), Cd(II) and Cr(VI) from an aqueous solution using chemically modified Bauhinia variegata leaves (CMBVL); a low cost adsorbent under different experimental conditions likes initial heavy metals concentration (20-500 mg/L), contact time (10-120 min), pH (1-7), and biosorbent dose (1-30 g/L). The biosorption of the selected heavy metals follow Langmuir isotherm more effectively rather than the Freundlich model. The maximum biosorption capacity (q(max)) of CMBVL for Pb(II), Cd(II) and Cr(VI) were; 92.592, 114.943, and 70.921 mg/g, respectively. Based on regression correlation coefficients (R-2) value the kinetic data were best fitted into second-order kinetic model rather than the first-order kinetic equation. The calculated thermodynamic parameters like standard enthalpy change (Delta H degrees), standard entropy change (Delta S degrees), and standard Gibb's free energy (Delta G degrees) indicated that the biosorption of the selected metals was an exothermic, spontaneous, and favorable process. Based on our results, it can be concluded that CMBVL could be effectively extended as biosorbent for the removal of heavy metals from industrial effluents.