Lead removal by polyacrylamide-bentonite and zeolite composites: effect of phytic acid immobilization

Polyacrylamide (PAA)-bentonite (B) and zeolite (Z) composites were prepared by direct polymerization of PAA in suspensions of B and Z. Phytate (Phy) immobilized onto the composites to obtain their Phy modifications. FT-IR and XRD were employed to characterize their structures. The sorption of Pb(2+) from various adsorption media onto the composites was then investigated. The reusability and storage characteristics of the adsorbents with and without Phy were also considered for Pb(2+) adsorption. All isotherms were L and H type of the Giles classification. The Phy adsorption capacities (X(M)) of PAA-B and Z lower than those of bare B and Z due to their surface coverage by PAA. The Phy modification decreased the Pb(2+) adsorption capacities of B and PAA-B but ascended those of Z and PAA-Z. However, Phy significantly increased the Langmuir equilibrium constants (K(L)) for all adsorbents. Ionic strength of the adsorption media was favorable for the adsorption capacity of PAA-B while not for that of PAA-Z. The chemical structure of the composites was not changed after five reuses and the storage foregoing. It is foreseen that the use of PAA-B and PAA-Z and their Phy modifications will provide practicality and effectiveness for Pb(2+) separation and removal procedures. The X(M) (mol kg(-1)) and K(L) (L mol(-1)) values for Pb(2+) adsorption from a model solution were 0.16 and 3625 for PAA-B, 0.18 and 5.1 x 10(5) for PAA-B-Phy, 0.28 and 13210 for PAA-Z and 1.65 and 2.0 x 10(5) for PAA-Z-Phy.