Adsorption studies of phosphate ions on alginate-calcium carbonate composite beads

Alginate-calcium carbonate composite beads was prepared by the sol-gel method and characterized by Fourier transform infra-red spectroscopy (FT-IR) and scanning electron microscope (SEM) instruments. Adsorption potential of phosphate ions have been studied on laboratory scale. The effects of contact time, adsorbent dosage, initial analyte concentration, pH and agitation speed were optimized at 298.15 K (25°C) in a single ion system. The adsorption process was in accordance with Freundlich model and pseudo second order kinetics. Thermodynamic parameters like ∆G°, ∆H° and ∆S° have also been determined. Negative values of ∆G establish the favorability of the process. Values of ∆H and ∆S indicate that the process was endothermic and during the adsorption of phosphate ions (PO 4 -3 ), less randomness takes place at the adsorbent-adsorbate interface.  Key words: Alginate-calcium carbonate, composite beads, phosphate ion adsorption.