Abstract
The aim of this study is to determine the adsorption performance of three types of adsorbents for removal of As(V) from water: Bayoxide® E33 (granular iron(III) oxide), Titansorb® (granular titanium oxide) and a suspension of precipitated iron(III) hydroxide. Results of As(V) adsorption stoichiometry of two commercial adsorbents and precipitated iron(III) hydroxide in tap and demineralized water were fitted to Freundlich and Langmuir adsorption isotherm equations, from which adsorption constants and adsorption capacity were calculated. The separation factor RL for the three adsorbents ranged from 0.04 to 0.61, indicating effective adsorption. Precipitated iron(III) hydroxide had the greatest, while Titansorb had the lowest capacity to adsorb As(V). Comparison of adsorption from tap or demineralized water showed that Bayoxide and precipitated iron(III) hydroxide had higher adsorption capacity in demineralized water, whereas Titansorb showed a slightly higher capacity in tap water. These results provide mechanistic insights into how commonly used adsorbents remove As(V) from water.
Highlights
The prevalence of toxic arsenic in drinking water is a significant worldwide problem
Results of As(V) adsorption stoichiometry of two commercial adsorbents and precipitated iron(III) hydroxide in tap and demineralized water were fitted to Freundlich and Langmuir adsorption isotherm equations, from which adsorption constants and adsorption capacity were calculated
Comparison of adsorption from tap or demineralized water showed that Bayoxide and precipitated iron(III) hydroxide had higher adsorption capacity in demineralized water, whereas Titansorb showed a slightly higher capacity in tap water
Summary
The prevalence of toxic arsenic in drinking water is a significant worldwide problem. Arsenic can be present in water in an oxidation state of –3, 0, +3 or +5, depending on the pH and redox potential of the water. It occurs in water most often as trivalent arsenite (H3AsO3, H2AsO3–, HAsO32– and AsO33–) and pentavalent arsenate (H3AsO4, H2AsO4–, HAsO42– and AsO43–). As(III), is usually present as an uncharged molecule (H3AsO3) in the water with low redox potential and a pH between 6.5 and 9.2, while pentavalent arsenate, or As(V), is usually present as a negatively charged molecule (H2AsO4–) in the water of the same pH range but with a more oxidized aerobic environment [3]
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