Author

Qiong Wang

Date of Award

12-2010

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

Advisor

Howard Patterson

Second Committee Member

Mitchell Bruce

Third Committee Member

Bruce L. Jensen

Abstract

Cu2+ and its compounds are serious environmental pollutants, and thus, the form and aqueous behavior of Cu2+ needs to be understood in order to effectively maintain water quality and ecological integrity of aquatic systems. Biosorption is an emerging technique where naturally occurring algae are used as a sorbing agent to control the aqueous free Cu2+ concentrations. Changes in the fluorescence intensity of algae in natural waters can be used as an indicator of aqueous free Cu2+ concentration, since Cu2+ is toxic to algae and can result in decreasing algal chlorophyll fluorescence intensity. This study was undertaken to use algal chlorophyll fluorescence intensity change as a diagnostic tool for the effect of Cu2+ stress to algae. Collected field water samples containing mixed algal assemblages were used to determine if additions of Cu2+ caused changes in algal chlorophyll fluorescence intensity after dosing immediately. The complexation reactions between the natural organic matter (NOM) containing the field samples and free Cu2+ ions were studied to determine the equilibrium properties of Cu2+-NOM bonding. The free Cu2+ concentration was determined by a copper ion selective electrode (CuISE). All the experiments were done at room temperature. Also, the biosorption of Cu2+ by freshwater algae was studied in this research to obtain the kinetic parameters for this process. Analyses were performed and based on emission spectra with excitation at 435 nm, 470 nm and 532 nm with a emission peak at 682 nm (corresponding to chlorophyll a, chlorophyll b & c and accessory pigments, respectively) using a spectrofluorometer. Algal chlorophyll fluorescence intensity changes were performed with Cu2+ additions at concentrations from 0.1 ppm to 10 ppm with triplicate tests. The comparisons of algal chlorophyll fluorescence intensity at each different Cu2+ adding concentration tell us that addition of Cu2+ at this range can reduce the algal chlorophyll fluorescence intensity and increased Cu2+ addition causes more decrease of algal chlorophyll fluorescence intensity. The present study examines the kinetics and equilibrium properties of freshwater algae with Cu2+ in the presence of NOM. Kinetic tests for the interactions of Cu2+ with algae in the presence of NOM, and Cu2+ with NOM were performed with spectrofluorometer and CuISE measurements. Kinetic results for Cu2+-algae in the presence of NOM were fitted to a pseudo-first-order model. The rate constants for Cu2+-algae with NOM presence are kp(Cu2+-Algae) = 0.0025 ± 0.0006 s-1 by CuISE, and kp(Cu2+-Algae)=0.0034±0.0011 s-1 by spectrofluorometer; for Cu2+-NOM interaction kp(Cu2+-NOM)=0.0015±0.0004 s-1 by CuISE. From these rate constant values, Cu2+ reacts with algae faster than with NOM. Moreover, the binding constants obtained by equilibrium studies are KCu2+-Algae=1.62 ±0.07 x 107M-1, KCu2+-NOM=5.52 ± 0.29 x 105M-1. These experimental results demonstrate that Cu2+ has a much higher affinity with algal sites than with NOM. Information about the kinetics and equilibrium properties for the formation of the complex of metal (Cu2+) with algal sites and with NOM is necessary in the design of algae as a cost-effective indicator to monitor public drinking water quality.

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