Adsorption of some essential amino acids and their mixture onto poorly crystalline hydroxyapatite [Adsorption des acides aminés essentiels et leur mélange sur l'hydroxyapatite mal cristallisée]

The adsorption of l-lysine,dl-leucine,two essential amino acids,and their equimolar mixture onto poorly crystalline hydroxyapatite,obtained by precipitation,is studied. the adsorption kinetics is relatively fast. isotherms were established,they are of freundlich and langmuir type. the affinity constant is more important for the l-lysine than for the dl-leucine. the amount of adsorbate adsorbed decreases with the increase of ratio ra (mg/ml). the calcium ions increase the adsorption,while phosphate ions inhibit it. the lateral load of the amino acid can modify the adsorption characteristics. the thermodynamic study shows that the adsorption is a spontaneous and exothermic process. the interactions adsorbate-adsorbent are electrostatic type.