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Home > Theses and Dissertations > Dissertations > All Dissertations > 1077

Date of Award

MINEQL+ is used in over 600 colleges and universities worldwide for teaching and research. MINEQL+ is the perfect tool for performing, visualizing, and managing chemical equilibrium calculations. For both the beginner and the professional, MINEQL+ is useful in education, research, and consulting. A Simple Approach to Complex Systems. MINTEQA2 is a equilibrium speciation model that can be used to calculate the equilibrium composition of dilute aqueous solutions in the laboratory or in natural aqueous systems. Complete self-contained system in zipped folder. Surely the quickest way to get up and running is to download a complete example in a single zipped folder (ca 360 kB ) that includes the ORCHESTRA executable, the object database, a thermodynamic database and input files defining a simple example system.

12-2012

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Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Environmental Toxicology

Advisor

Carraway, Elizabeth R

Committee Member

Klaine , Stephen J

Committee Member

Schlautman , Mark A

Committee Member

van den Hurk , Peter

Abstract

The dissolution and aggregation of metal oxides nanoparticles (NPs) in aqueous solution not only alter the abundance and toxicology of NPs, but also makes the effective assessment and the correct interpretation of effects of NPs on organisms challenging. The extent to which these processes (dissolution and aggregation) occur largely depend on pH, ionic strength, dissolved natural organic matter (NOM) and NPs characteristics. This study investigated the dissolution and aggregation behavior of the four metal oxide NPs (nZnO, nCuO, nFe2O3 and nTiO2) in aqueous solution as influenced by pH, ionic strength and NOM and examined the toxicity of these NPs to Daphnia magna and interpreted the toxicity in terms of NPs'behavior in aqueous solution.
The dissolution of NPs in distilled and dionized (DDI) water, culture (FETAX) solution, solutions of varying pH, ionic strength and NOM content was investigated. Differences in the dissolution patterns in different solution conditions were observed among the NPs, with some NPs (nTiO2.) showing low dissolution under all solution conditions. Visual Minteq model showed that the distribution of dissolved metal oxides NPs species was regulated by pH and NOM. The experimental dissolution data were corroborated by Visual Minteq and by the empirical double exponent dissolution rate model.
In the aggregation investigation, the aggregation behavior and fractal dimensions of the metal oxides NPs were studied in solutions such as DDI, FETAX solution, solutions of varying pH, ionic strength and NOM content. The rate of aggregation was found to increase with ionic strength and to decrease with increase in NOM concentration. Increased aggregation corresponded to lower fractal dimensions and increased sedimentation.
Arising from the dissolution and aggregation investigations, the interaction of NOM with NPs in aqueous solution was examined. Specifically, the influence of the NOM on NPs dispersion at different pH values was investigated using TiO2 NPs selected due to its low dissolution over a wide pH range. With the data suggesting that NPs dispersion is pH dependent, sorption studies of NOM to TiO2 NPs at different pH values were conducted and the sorption data obtained were used to interpret the dispersion results. The sorption data were also fitted on the nonlinear Langmuir model. This study also examined the possible fractionation of NOM upon sorption to NPs. The results demonstrated that fractionation occurs upon sorption and that both low pH and high ionic strength can enhance fractionation.
The NPs toxicity to Daphnia magna was assessed at two levels of biological organization: organism level with mortality at 48 h (LC50) used as the endpoint and the cellular level with four biomarkers, glutathione- S -transferases (GST), thiobarbituric acid reacting substances (TBARS), oxidized glutathione (GSH) and metallothionein (MT) used as endpoints. The results suggested that the toxicity observed from NPs in organism and cellular levels is a contribution of both the NPs and the dissolved metal ions. The results further showed that NOM and ionic strength have mitigative effects on NPs toxicity to Daphnia magna through sorption and aggregation processes respectively.

Recommended Citation

Mwaanga, Phenny, 'THE BEHAVIOR AND TOXICITY OF METAL OXIDE NANOPARTICLES IN AQUEOUS SOLUTION' (2012). All Dissertations. 1077.
https://tigerprints.clemson.edu/all_dissertations/1077

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Visual MINTEQ is a freeware chemical equilibrium model for the calculation of metal speciation, solubility equilibria, sorption etc. for natural waters. It combines state-of-the-art descriptions of sorption and complexation reactions with easy-to-use menus and options for importing and exporting data to/from Excel. Chemical equilibrium modelling has never been easier! Primer premier keygen crack.

The code, originally built on USEPA’s MINTEQA2 software, is maintained by Jon Petter Gustafsson at KTH, Sweden, since 2000.

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