A promising chitosan/fluorapatite composite for efficient removal of lead (II) from an aqueous solution

Abstract

Lead (II) is one of the most important metal ion pollutants commonly found in industrial wastewater. It is harmful to the animal kingdom, and prolonged exposure can cause severe health trouble including cancer. Therefore, its removal to a permissible level is necessary for an eco-friendly and sustainable environment. The use of low-cost chitosan-based composite material as an adsorbent can be a promising approach for Pb(II) decontamination. In this study, a novel chitosan/fluorapatite (Cs-Fap) composite has been prepared from chitosan (Cs) and fluorapatite (Fap) for the efficient removal of Pb(II) from water. Exploration of the effect of contact time, solution pH, initial Pb(II) concentration, adsorbent dosage, and the temperature was performed to understand the uptake process. Pb(II) adsorption performance was compared among Cs, Fap, and Cs-Fap composite. Pb(II) adsorption was fast and approached equilibrium in 20 min. Maximum Pb(II) accumulation was achieved at pH 4.0 for an optimum dose of 2g/L. Pb(II) adsorption kinetics data followed a pseudo-second-order (PSO) model, while equilibrium isotherm data was best described by the Langmuir equation nicely. The maximum uptake capacity (mg/g) follows the order: Cs-Fap (60.24) > Fap (48.31) > Cs (43.29) at pH 4.0. The thermodynamic analysis revealed (ΔG < 0, ΔS > 0, and ΔH > 0) that the uptake process was feasible, endothermic, and spontaneous. The proposed mechanism of Pb(II) uptake involved physisorption, ion-exchange, electrostatic attraction, surface complexation, and precipitation. The Cs-Fap composite showed an excellent regeneration capacity up to four subsequent cycles. The results of this study showed that the Cs-Fap composite is promising for Pb(II) uptake, and it can be utilized as an adsorbent for the uptake of other metal ions from real environmental samples.