The objective of this work was to propose an alternative use for ephedra residue (ER) as untreated biosorbents for the removal of Pb 2+ ions from aqueous solutions. Biosorption studies were conducted as a function of the solution pH, contact time and initial metal ion concentration. The biosorption kinetics was determined by fitting second-order kinetic models to the experimental data, being described by the pseudo-second-order model (R 2 > 0.99). Both Langmuir and Freundlich sorption models fit the experimental sorption equilibrium data, with Langmuir providing the best fit (R 2 > 0.97). According to the Langmuir equation, the maximum uptake capacity for Pb 2+ ions was 1.0 mmol/g at 298K. A comparison of the maximum sorption capacity of several untreated biomaterial-based residues showed that the ER is a suitable candidate for use as biosorbents in the removal of Pb 2+ ions from aqueous solutions.
