Abstract
Chemical compositions of natural zeolites, porcelanite (opal-CT) and local sands were determined
by X-ray fluorescence (XRF) and correlated with their Pb(II) removal efficiencies. Zeolites and
porcelanite were from the Mikawer, Aritain and Hannon areas in Jordan. Sands (white, red and
yellow) were from the United Arab Emirates (UAE). The effect of Pb(II) concentration and zeolite
dosage on removal efficiency was investigated at 25.0˚C using the batch equilibrium method.
Commercial kaolinite, silica and alumina were also studied for comparison. Removal efficiencies,
in mg Pb(II)/g adsorbent, were: 76.9, 52.7 and 42.1 for Hannon, Mikawer and Aritain zeolites, respectively;
58.2 for porcelanite; 29.7, 11.0 and 8.5 for yellow, red and white sand, respectively; 7.2,
3.3 and 1.3 for kaolinite, silica and alumina, respectively. XRF data indicate that adsorbents with
intermediate molar ratios of Si/Al, in the range 2.70 - 2.93, are most efficient in Pb(II) removal.
Scanning electron microscope (SEM) images of adsorbents suggest that morphology, in addition to
chemical composition, plays a key role. In particular, a combination of factors, including shapes
and sizes of crystals, channels in zeolites and pores in porcelanite, appear to favor removal of
Pb(II).
