Removal of Lead(II) from Aqueous Solution using Papaya Seed Carbon: Characteristics and Kinetics Study

Carbonization of raw biomass directs an attractive approach for improvement of lead(II) uptake from aqueous solutions. Papaya seed (PS) powder was carbonized by treating with conc. H2SO4 and characterized using SEM and FTIR. Experimental parameters that influence the adsorption of Pb(II) onto PSC such as pH, adsorbent dose, contact time and initial concentration of metal ions have been investigated. The adsorption of Pb(II) increased with the increase in contact time and reached equilibrium with in 2h. The maximum uptake of Pb(II) was found at pH 5.0. The kinetic data were analysed using three adsorption kinetics models; the pseudo-first, second order kinetics and intra-particle diffusion. The results showed that the pseudo-second order model fits the experimental data very well. The equilibrium data have been analyzed using Langmuir and Freundlich isotherm models. The batch equilibrium data fitted well to be Langmuir isotherm. Maximum adsorption capacity of PSC for Pb(II) was 68.4 mg/g which is relatively large compared to most of the biomass adsorbents as reported. Desorption experiments were carried out using HCl solution and the recovery of Pb(II) from PSC was found 98.5 % using 0.2 M HCl. Desorption experiments showed the feasibility of the regeneration of PSC. Study concluded that PSC has a good potential as an adsorbent to remove toxic metals like Pb(II) from water