Sol-gel synthesis, magnetic and methylene blue adsorption properties of lamellar iron monophosphate KMgFe(PO4)2

The alkali magnesium iron phosphate KMgFe(PO4)(2) was synthesized by sol gel method and was characterized by XRD, SEM, IR and magnetic susceptibility measurements. The purity and the structure of the obtained phase were analyzed by X-ray diffraction and structural refinement. The prepared sample crystallized in monoclinic system, space group C2/c, and adopted a lamellar structure. The chemical composition and morphology were confirmed by scanning electron microscopy. IR spectroscopy verified the presence of only PO43- group in the structure. Magnetic measurements revealed an antiferromagnetic behavior with T-N = 2.7 K. The methylene blue adsorption process was evaluated as a function of various operating parameters such as contact time, pH, temperature and concentration. The experimental data were analyzed using several kinetic models: the pseudo first order, pseudo second order and intraparticle diffusion. The pseudo second order model described suc-cessfully the adsorption of methylene blue on the synthesized compounds. The experimental isotherm data were analyzed by the Langmuir, Freundlich and Temkin models. The equilibrium data were well-fitted with the Langmuir model.