Cation Exchange Mechanism of Divalent Metals ions onto Synthetic NaX and LTA Zeolites: Efficiency and Selectivity

Abstract

In this investigation, the removal of divalent heavy metals by two types of zeolites has been studied. The mechanism of cation exchange for Cu 2+ , Ni 2+ , Cd 2+ and Pb 2+ on NaX Faujasite and Linde type A (LTA) zeolites was studied. Both zeolites are very efficient in divalent heavy metals removal from water. Ion exchange isotherms were performed and the thermodynamic parameters were calculated as well. Kielland plots showed that the order of selectivity is not the same for both the zeolites. For NaX it followed the following order Pb 2+ > Cu 2+ > Cd 2+ > Ni 2+ while for LTA the order is Pb 2+ > Cd 2+ > Cu 2+ > Ni 2+ . Exchange velocity (kw) and the radii of the hydrated metals ions are involved in determining this order of selectivity.

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“…Ion-exchange isotherms of different kinds of zeolite powders in copper­(II) ions solutions. Data on zeolite 4A and phillipsite are taken from Ezzeddine et al and Colella et al, respectively. Dashed lines are guides for the eye.…”