Lead and copper scavenging from aqueous solutions using Eucalyptus camaldulensis derived activated carbon: equilibrium, kinetics and sorption mechanism

In this study, activated carbon was derived from Eucalyptus camaldulensis (Ec(activ)), activated though thermochemical (phosphoric acid) treatments and investigated for its efficiency to remove lead (Pb2+) and copper (Cu2+) from aqueous solutions. The contact time for equilibrium adsorption was estimated to be about 30 min, with a higher removal efficiency of Pb2+ compared to Cu2+ with insignificant removal after 2 h of contact time until 12 h, suggesting no adsorption within 2-12 h. The metal uptake and removal efficiency was almost two fold for Cu2+ while an even greater difference was seen for Pb2+ when the pH was varied from 2.5 to 5.5. A dose of 1.0 g of Ec(activ) was deemed to be optimum for the highest uptake in the case of Pb2+ while for Cu2+, the removal efficiency increased linearly with the increase in the dose of Ec(activ) from 0.2 to 1.8 g. A 30% and 40% difference in the removal efficiency of Pb2+ and Cu2+, respectively, was observed by increasing the initial solution concentration from 50 to 250 mg L-1 with an increase in the metal uptake of about 123 and 30 mg g(-1) for Pb2+ and Cu2+, respectively. Among the isotherm models, the Langmuir isotherm showed the best fit to the experimental data for both Pb2+ and Cu2+, as confirmed by the respective high coefficients of determination. Finally, the kinetic behavior was best described by the pseudo-second-order model suggesting chemisorption of both heavy metal ions onto Ec(activ).