Lanthanum (III) encapsulated chitosan-montmorillonite composite for the adsorptive removal of phosphate ions from aqueous solution

In the present work, lanthanum (III) encapsulated chitosan-montmorillonite composite (La-CS-MMT) was prepared as an adsorbent for the effective removal of phosphate ions from aqueous solution. Characterization of the adsorbent using FT-IR, XRD, SEM with EDX, TGA and DTA techniques were carried out. Batch adsorption experiments were carried out to optimize the effects of various operating parameters viz., shaking time, initial concentration of phosphate ions, dosage, competitor co-existing ions, pH and temperature. Phosphate ions adsorbed effectively on La-CS-MMT composite through hydrogen bonding and by outer-sphere complex formation mechanism. Freundlich isotherm model fit well with the equilibrium isotherm data. The experimental values of ∆G°, ∆S° and ∆H° revealed that the nature of adsorption was feasible, spontaneous and exothermic. The kinetic study was well fitted with pseudo-second-order model. Regeneration study of the spent La-CS-MMT-P composite was carried out upto five cycles and found that about 70% of adsorption efficiency was retained.