Adsorptive removal of copper(II) from aqueous solutions on activated carbon prepared from Tunisian date stones: Equilibrium, kinetics and thermodynamics

Abstract

In this study, activated carbon produced from Tunisian date stones, a low-cost agricultural by-product, by chemical activation using H3PO4 as an activator was used as adsorbent for the removal of copper(II) ions from aqueous solutions. To optimize the preparation method, the effect of the main process parameters (such as acid concentration, impregnation ratio, and temperature of pyrolysis step) on the performances of the obtained activated carbons was studied. The optimal activated carbon was fully characterized considering its adsorption properties as well as its chemical structure and morphology.Optimum adsorption conditions were determined as a function of pH, initial copper concentration, contact time and temperature of solution for copper(II) removal. The results showed that the adsorption of copper(II) onto activated carbon produced by the optimum conditions was maximal at about pH 5.0. The rates of adsorption were found to conform to the pseudo-second-order kinetic model. The application of the intra-particle diffusion model revealed that the adsorption mechanism of copper(II) is rather a complex process and the intra-particle diffusion is involved in the overall rate of the adsorption process but it is not the only rate-controlling step. The isotherm equilibrium data were well fitted by the Langmuir and Dubinin–Radushkevich isotherm models with a monolayer maximum adsorption capacity of 31.25mg/g. According to the experimental results, the adsorbent derived from this material is expected to be an economical product for metal ion remediation from water and wastewater.