Kinetics and Equilibrium Studies of the Biosorption of Cu(II)by Algae in the Presence of Natural Organic Matter

Author

Qiong Wang

Date of Award

12-2010

Level of Access Assigned by Author

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 k_{p(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 k_{p(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 K_{Cu²⁺-Algae}=1.62 ±0.07 x 10⁷M^-1, K_Cu²⁺-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.

Recommended Citation

Wang, Qiong, "Kinetics and Equilibrium Studies of the Biosorption of Cu(II)by Algae in the Presence of Natural Organic Matter" (2010). Electronic Theses and Dissertations. 895.
https://digitalcommons.library.umaine.edu/etd/895