Date of Award

1994

Document Type

Honors Thesis (Open Access)

Department

Colby College. Chemistry Dept.

Advisor(s)

D. Whitney King

Second Advisor

Thomas W. Shattuck

Abstract

A fully automated luminal-based chemiluminescence flow injection analysis system has been developed for rapid detection of Fe(IT) at natural levels in natural water systems. Similar detection limits are achieved for H202 by fluorometry using an enzyme mediated oxidation of the reagent p-hydroxyphenylacetic acid. Using these analytical systems, the rates of Fe(IT) oxidation by dissolved oxygen in 0.7 M NaO have been measured for nanomolar concentrations of Fe(II) over the pH range 7.0 to 8.3. When the production and decomposition of H202 in the system were considered, measured rates were in excellent agreement with a model based on previously reported rate constants determined using pM levels of Fe(ll). These results show that ·02-and .OH intermediates produced as a result of Fe(II) oxidation remain effective as Fe(II) oxidants in these controlled conditions. The kinetic model for Fe(ll) oxidation also allows prediction of steady state H202 concentrations that can result from the oxidation of Fe(II). Concentrations increase exponentially with increasing pH. At pH 8.2 the predicted H202 concentration is 220 nM. Laboratory measurements are in good agreement with predicted concentrations. Rates of Fe(lIl) photoreduction have been measured as a function of pH, Cl concentration, and wavelength using a solar simulator. Photoreduction rates are first order with respect to Fe(llI) and decrease rapidly with increasing pH. Through wavelength specific quantum yield measurements, it was determined that in solutions with high Cl-Ievels, both Fe(OH)2 and FeCh are photoreactive.

Keywords

Water chemistry, Chemiluminescence, Iron, Iron oxides, iron cycling, aquatic systems

Download

Included in

Chemistry Commons

Share

COinS