Date of Award:

12-2018

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Civil and Environmental Engineering

Committee

Joan E. McLean

Committee

Laurie S. McNeill

Committee

Astrid R. Jacobson

Abstract

Thallium (Tl) is a rare heavy metal in drinking water, but its extreme toxicity makes its removal crucial to consumer health. Traditional treatment methods do not work for Tl in sources with high concentrations of ions like calcium (Ca+2) and potassium (K+), as they are removed preferentially to Tl. A treatment method that specifically targets Tl must be applied. Pilot studies conducted in Park City Utah found that pyrolusite, a manganese oxide ore, will remove Tl to very low concentrations in the presence of competing ions but because this method is not common, further study was required. This study investigated the mineral composition of the pyrolusite and where, within the material, Tl was held. Calcite is known to accumulate Tl so tests were done looking at Tl accumulation onto pyrolusite with and without calcite on the surface in three water qualities: one with high pH and chlorine (Cl2) and low concentrations of the interfering ions Ca, K, chloride (Cl-) predicted to promote Tl removal, one with low pH and Cl2 and high concentrations of interfering ions predicted to limit Tl removal, and one with a moderate pH used for comparison. The likelihood of this Tl to stay on the media surface with changes in water chemistry was also tested. It was seen that Tl does accumulate in calcite on the media surface. Both pyrolusite media showed a high capacity for Tl and media without calcite exhibited a preference for Tl over K. Calcite dissolved with changes in pH which led to the conclusion that its formation on the media surface must be closely monitored as it may increase the risk Tl release into the drinking water system.

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