Expeditious and enhanced sequestration of heavy metal ions from aqueous environment by papaya peel carbon: a green and low cost adsorbent

Abstract

In this study, papaya peel carbon (PPC) has been explored as a potential adsorbent for the removal of Pb(II), Cu(II) and Ni(II) from their aqueous phases. Optimum adsorption conditions such as contact time, pH, initial metal ion concentrations, adsorbent dosage and temperature were determined. Optimum pH for the removal of Pb(II) and Ni(II) was found to be 6, while for Cu(II) it was 5. Maximum monolayer adsorption capacity (q(m)) was found to be 40.98, 38.02 and 32.25 mg g(-)(1) for Pb(II), Cu(II) and Ni(II) ions, respectively. To study the kinetic parameters and mechanism of adsorption process, pseudo-first-order, pseudo-second-order, intraparticle diffusion and Elovich kinetic models were elucidated. D-R adsorption isotherm model best described adsorption of Pb(II) and Ni(II) ions onto PPC, whereas Freundlich adsorption isotherm described adsorption of Cu(II). To further predict the nature of adsorption, thermodynamic parameters such as Delta G degrees, Delta H degrees and Delta S degrees were calculated and positive values of Delta H degrees indicated endothermic nature of the process. Thus overall results confirmed that PPC can be effectively used as an alternative and low-cost adsorbent for the removal of heavy metal ions Pb(II), Cu(II) and Ni(II).