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).
Highlights
Pb(II) in the environment has a high level of toxicity and poses a serious hazard to human and animal health
Scanning electron microscope (SEM) images have been employed in assessing adsorptive surfaces and are regularly featured in reports on the removal of heavy metals by a variety of surfaces [8]-[11]
It is apparent that zeolites and porcelanite are highly efficient in removing Pb(II) from aqueous solutions
Summary
Pb(II) in the environment has a high level of toxicity and poses a serious hazard to human and animal health. Column filtration and batch equilibrium by low cost adsorbents are the most common methods used in removing Pb(II) and other toxic heavy metals from wastewaters. UAE sands were shown to be efficient adsorbents for the removal and recovery of Pb(II) and other heavy metals from aqueous solutions [1] [2], and for the removal and speciation of Cr(III) and Cr(VI) [3] [4]. Reports on heavy metal removal from solutions by sawdust [5], eggshell [6], bentonite, molasses and fly ash [7] have included X-ray fluorescence (XRF) data on these adsorbents. Scanning electron microscope (SEM) images have been employed in assessing adsorptive surfaces and are regularly featured in reports on the removal of heavy metals by a variety of surfaces [8]-[11]. Zeolites have been successfully used to remove uranium (IV) from contaminated waters [13] and oil from palm oil mill effluent [14]
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