Removal of Pb(II) from aqueous solutions by Phytolacca americana L. biomass as a low cost biosorbent

Abstract

Screening a new biosorbent with low cost and high efficiency from a native plant material is a key to the adsorption of heavy metal ions from wastewater. In this study, the potential of Phytolacca americana L. as a biosorbent for Pb(II) removal from aqueous solutions was investigated. Experiments were performed to evaluate the effect of biosorbent dosage, pH, initial Pb(II) concentration and contact time on the Pb(II) removal. The results indicated that the hydroxyl, carboxyl and amine groups may take part in Pb(II) binding. HNO3-modified P. americana (HPAL) showed a significant higher uptake capacity compared to original P. americana (PAL) (p < 0.05). A dose of 20 g L−1 of biosorbents in solutions with an initial pH of 6.0, an initial Pb(II) concentration of 30 mg L−1 and a contact time of 120 min resulted in the maximum Pb(II) removal efficiency. The Freundlich isotherm gave a better fit than the Langmuir isotherm revealed that the biosorption was potentially multilayer. Further, the adsorption kinetics followed a pseudo second-order model, which implied that the biosorption was mainly a chemisorption process. The thermodynamic properties showed that the Pb(II) adsorption onto the P. americana biomass was feasible, spontaneous and exothermic in nature. Both physisorption and chemisorption were involved in the biosorption of Pb(II) onto the surface of P. americana biomass through electrostatic interaction and ion exchange. Additionally, desorption studies revealed promising regeneration potential of these biosorbents. The present study showed that P. americana biomass could be used as a low-cost, eco-friendly and effective biosorbent for the Pb(II) removal from wastewater.