Lead adsorption from aqueous solutions by a granular adsorbent prepared from phoenix tree leaves

Abstract

In this study, a granular adsorbent was prepared from phoenix tree leaf powder with bentonite as the binder. The granular adsorbent was characterized by TG, BET and SEM analyses. The maximum specific surface area and pore volume were 166.3 m² g⁻¹ and 0.276 cm³ g⁻¹, respectively, after the granular adsorbent was calcined at 500 °C. Effects of pH, adsorption time and initial metal ion concentration on the adsorption of Pb²⁺ by 500 °C calcined granular adsorbent were investigated in batch experiments. Higher pH was favorable for the adsorption process and significant release of Na⁺, K⁺ and Mg²⁺ were observed, assuming the predominant Pb²⁺ adsorption mechanism was ion exchange. The adsorption could attain equilibrium within 24 h with a gradual increase of the solution pH. The kinetics data were analyzed using three adsorption kinetic models: the pseudo-first-order, pseudo-second-order and intraparticle diffusion equations. Results show that intraparticle diffusion or chemical adsorption is the rate-limiting step depending on the adsorption time. The adsorption isotherms best fitted the Langmuir–Freundlich model and the maximum Langmuir adsorption capacity was found to be 71 mg g⁻¹. This novel granular adsorbent has proven to be a potential inexpensive adsorbent for Pb²⁺ removal from aqueous solutions.