ARSENITE REMOVAL FROM AQUEOUS SOLUTION BY MIXED MINERAL SYSTEMSI. REACTIVITY AND REMOVAL KINETICS
1Egirani, D.E., 2Baker, A.R and 2Andrews, J.E
1Faculty of Science, Niger Delta University, Wilberforce Island, Nigeria
2 Schools of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom
ABSTRACT
This study investigates the reactivity and removal kinetics of arsenite on mixed mineral
systems from aqueous solution related to contaminated waters. The sorbents used were
kaolinite, montmorillonite, goethite, and their mixtures. The effects of, proton coefficient,
and sorption kinetics were studied at room temperature (23 ± 2°C). Reactivity studies
demonstrate reduction in proton coefficient and the acidity of reactive sites by mixed
mineral systems, thus impeding arsenite removal by proton exchange. Kinetic studies
demonstrate three phase reactions attributed to outer sphere complexation, inner sphere
complexation and intra-particle diffusion. Mineral mixing reduced the mass transfer rate
of arsenite for kaolinite/montmorillonite in all reaction phases. The behaviors of the mixed
mineral systems in arsenite sorption suggest that different reactive sites were involved at
the onset of sorption, with reactions and sorption ending in intra particle diffusion over
time. Mineral mixing increased % sorption when compared with the single mineral
systems. % sorption was a function of the surface area of the mineral sorbent.
Key words: Arsenite, removal, reaction, kinetics, mixed mineral systems.
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