Single and competitive adsorption of Cu2+ and Pb2+ by tea pulp from aqueous solutions

Background: Removal of heavy metals by bioadsorbents is one of the effective and inexpensive methods for water and wastewater treatment. The aim of this study was to investigate the ability of tea pulp in order to remove Cu2+ and Pb2+ metals in two states of adsorption (single element and two elements) from aqueous solutions. Methods: Experiments were performed on synthetic and real samples at ambient temperature. The effect of solution pH, adsorbent dose, contact time, and initial concentration on single and competitive removal of copper metals and lead was studied. Adsorption kinetics and adsorption isotherms were analyzed by pseudo-second-order kinetic equations, Elovich model and intraparticle diffusion, Freundlich and Langmuir equations, respectively. Results: The maximum adsorption capacity for copper and lead was observed at pH = 5-8 and pH = 4-8, respectively. Maximum adsorption capacity for copper and lead by tea pulp in single-element solution (single) was 37.17 and 48.54 mg/g and in two-element solution (competitive), was 28.41 and 43.47 mg/g, respectively. The adsorption reaction of heavy metals by tea pulp followed the Longmuir isotherm and pseudo-second-order kinetic models. Conclusion: Tea pulp as an inexpensive bioadsorbent is able to remove about one-third of the copper, and approximately, half of lead from aqueous solutions, so its use in the treatment of aqueous solutions will be beneficial.