Phosphorus adsorption onto an industrial acidified laterite by‐product: equilibrium and thermodynamic investigation

Abstract

ABSTRACTThe present research investigates the uptake of phosphate ions from aqueous solutions using acidified laterite (ALS), a by‐product from the production of ferric aluminium sulfate using laterite. Phosphate adsorption experiments were performed in batch systems to determine the amount of phosphate adsorbed as a function of solution pH, adsorbent dosage and thermodynamic parameters per fixed P concentration. Kinetic studies were also carried out to study the effect of adsorbent particle sizes. The maximum removal capacity of ALS observed at pH 5 was 3.68 mg P g−1. It was found that as the adsorbent dosage increases, the equilibrium pH decreases, so an adsorbent dosage of 1.0 g L−1 of ALS was selected. Adsorption capacity (qm) calculated from the Langmuir isotherm was found to be 2.73 mg g−1. Kinetic experimental data were mathematically well described using the pseudo first‐order model over the full range of the adsorbent particle size. The adsorption reactions were endothermic, and the process of adsorption was favoured at high temperature; the ΔG and ΔH values implied that the main adsorption mechanism of P onto ALS is physisorption. The desorption studies indicated the need to consider a NaOH 0.1 M solution as an optimal solution for practical regeneration applications. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.