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 Just Accepted

This article has been peer reviewed and accepted for publication. It is in production and has not been edited, so may differ from the final published form.


Effectiveness of various sorbents and biological oxidation in the removal of arsenic species from groundwater

Anna Corsini, Lucia Cavalca, Gerard Muijzer, Vincenza Andreoni, Patrizia Zaccheo

Abstract

Batch experiments were conducted to evaluate As(III) and As(V) adsorption capacity of five sorbents (i.e., biochar, chabazite, ferritin-based material, goethite and nano zero-valent iron) in artificial systems at autoequilibrium pH (MilliQ water without adjusting the pH) and at circa neutral pH (i.e., Tris-HCl, pH 7.2). At autoequilibrium pH, the effects of sorbents on removal of 200 μg L-1 As ranged from very high efficiency for iron-based sorbents to ineffectiveness for biochar and chabazite. When tested at circa neutral pH, the sorbents were capable to remove between 17% and 100% of As(III) and between 3% and 100% of As(V) in the following order of sorbents: biochar < chabazite < ferritin-based material < goethite < nano zero-valent iron. The study also highlighted that chabazite, a ferritin-based material, and nano zero-valent iron oxidized As(III) to As(V) and that the ferritin-based material was also able to reduce As(V) to As(III). When tested in naturally arsenic-contaminated groundwater, a marked decrease in the removal effectiveness of nano zero-valent iron and goethite occurred (60% and 12%, respectively), due to possible competition with phosphates and manganese. The usefulness of a biological oxidation step was evaluated in one-phase process (As(III) bio-oxidation in conjunction with As(V) adsorption) and in two-phase process (As(III) bio-oxidation followed by As(V) adsorption), both in As(III)-spiked Tris-HCl and in natural groundwater systems. As(III) oxidation was performed by resting cells of Aliihoeflea sp. strain 2WW, and arsenic adsorption by goethite. In the one-phase process As removal in Tris-HCl was >95%, while in groundwater it decreased to 85%. More effective was the two-phase process that removed up to 95% As in groundwater leaving in solution 6 μg L-1 arsenic, thus meeting the limit of 10 μg L-1 imposed by World Health Organization. These results can be used in the scaling up of a two-phase treatment, with bacterial oxidation of arsenic used in combination with goethite sorption.

EN13210  Accepted 25 May 2014
 
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