Graduation Year

2009

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Maya Trotz, Ph.D.

Co-Major Professor

Daniel Yeh, Ph.D.

Committee Member

Mark Stewart, Ph.D.

Committee Member

Norma Alcantar, Ph.D.

Committee Member

Jeffrey Cunningham, Ph.D.

Keywords

Adsorption, Langmuir, Freundlich, Diffusion coefficient, Electron potential.

Abstract

This research evaluated the effectiveness of a commercially available adsorbent, Kemiron, to remove arsenic from conditions representative of landfill leachate. Kemiron was identified as an iron oxide of 39.8 m

2/g surface area, 44 % of which resided in the less than 3 nm pore size range. Batch experiments of As(V) and As(III) were conducted with particle sizes either ≤38 μm and in the range 500 – 600 μm with equilibrium being reached in the smaller particles in ~ 36 hours and estimated at 374 hrs for the larger particles. Ionic strength did not affect the mass loadings of As(V) and As(III) which approached 80 mg/g sorbent and greater than 90 mg/g respectively at pH 7. The effect of Se(IV) and Ni(II) was greater on As(III) than on As(V) sorption with as much as a 40% reduction in As(III) sorption in the presence of a similar amount of Se(IV). Sulfate, calcium and carbonate reduced As(III) sorption whereas calcium enhanced As(V) sorption. As removal tested in synthetic landfill leachate under both young and old landfill conditions indicated that pH, ORP, and Se(IV) as a co-contaminant with 1:1 mg/L concentration to As were the most significant key factors that influence As adsorption. Over 90% of 5 mg/L As(V) as initial concentration was removed at pH 7.2 within an operating range of 197 and 371.6 mV of ORP and 99% removal was also

achieved at ~ pH 11 under the range of -335.7 and 9.1 mV of ORP where the latter condition would be unlikely in real leachate. Preliminary experiments with real leachate solutions show similar sorption behavior for As(V) though the total amount removed was reduced. Whilst this work shows the potential for sorption technology as a treatment option for heavy metal removal from landfill leachate, further tests are definitely needed to determine the various pre-treatment options needed before real leachate solutions can be treated. Many commercially available sorbents have been developed for contaminated drinking waters and this is the first study that has looked at their application to the more complex leachate matrix.

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