Separation Science and Technology, Vol.39, No.2, 287-300, 2004
Novel spherically granulated inorganic ion exchangers based on aluminophosphatesilicate and ferrophosphatesilicate gels
Novel porous sodium aluminophosphatesilicate (APS) with the empirical formula Na4.01Al4.02PSi17.99O46.5.18H(2)O and sodium ammonium ferrophosphatesilicate (FPS) with the empirical formula Na-0.32(NH4)(2.44)Fe6.17PSi8.9O30.9 . 14.3H(2)O were synthesized by the sol-gel method as the spherically granulated beads. The APS and FPS were characterized by elemental analysis, x-ray diffraction, Al-27, P-31, Si-29 MAS NMR, Fe-57 Mossbauer spectroscopy, and thermal gravimetric analysis (TGA). Ion exchange of some divalent metal cations (Pb2+, Cd2+, Cu2+, Ni2+, Zn2+) and sodium by APS and FPS was studied in batch conditions. It was found that APS and FPS have a cation exchange capacity of about 2.5 and 2.0 mEq/g respectively. The ion exchange isotherms for divalent cations were determined. The investigated APS exhibits a high affinity toward lead and copper ions; moderate affinity towards zinc, nickel, and cadmium ions; FPS exhibits a high affinity towards lead and copper cations; moderate affinity to zinc and cadmium cations; and a low affinity to nickel cations in 0.1-M NaNO3 solutions. Due to low cost and high process ability of manufacture and the spherical form of the particles, we can suppose that these sorbents could be used for purification of some industrial waste waters from toxic heavy metals.
Keywords:sol-gel technique;ion exchangers;amorphous gels;waste waters purification;inorganic materials;porous materials