Irreversible sorption of Pb(II) from aqueous solution on breadfruit peel to mitigate environmental pollution problems

Development of efficient and environmentally friendly methods to remove toxic pollutants from aqueous systems is a requirement to mitigate ever increasing environmental pollution problems. In this context, Artocarpus altilis (breadfruit) peel (BP), a waste material, can be used as a low-cost adsorbent for the removal of Pb(II) ions from synthetic pollutant solutions. The extent of removal of Pb(II), under optimized conditions in experimental batch experiments, is determined to be 82.0%, which is decreased in highly ionic environments, partly due to competition for a limited number of active adsorption sites, indicating the necessity of optimizing experimental parameters for the most efficient removal. Regression analysis and error function values evaluated for isotherm models associated with different adsorption mechanisms, namely Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Redlich-Peterson and Sips, indicate that the best fitted model is the Sips followed by the Langmuir model with adsorption capacities (q_max) of 78.50 mg g^-1 and 85.42 mg g^-1, respectively. Thermodynamics arguments support the spontaneous and exothermic behavior of the Pb(II)-BP adsorption system, while adsorption kinetics of the system provides evidence for the applicability of the pseudo second order model with a rate constant of 0.504 g mg^-1 min^-1.