BIOSORPTION OF LEAD HEAVY METAL ON PRICKLY PEAR CACTUS BIOMATERIAL: KINETIC, THERMODYNAMIC AND REGENERATION STUDIES

Abstract

The potential of Tunisian prickly pear cactus as a low-cost adsorbent for Pb(II) ions from aqueous solution was investigated in batch mode. To determine the optimum adsorption conditions, experiments were conducted varying the operating parameters, as follows: pH of the solutions (2-10), initial concentration of metal ions (0.98-2.4 mmol/L) and temperature (30-60 °C). The adsorption isotherm data were analyzed by applying the Langmuir, Freundlich, Dubinin–Raduskevich, Temkin and Redlich–Peterson models. The experimental results were better fitted by the Freundlish model. The pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion models were applied to the description of the kinetic data. The best fit was achieved for the pseudo-second order model, and the presence of both film and intraparticle diffusion mechanisms was demonstrated. Thermodynamic studies indicated that the biosorption on the cladode powder is an exothermic and chemical process. The desorption/regeneration process was also investigated. The obtained results revealed over 90% desorption of Pb(II) metal ions from the total metal-loaded mass of the adsorbent and good stability of the cactus adsorbent for four successive adsorption/desorption cycles.