Effects of pH, Electrolyte Concentration, and Organic Acid Coating on the Aggregation Kinetics of Hematite Nanoparticles
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Series/Report no.:Ohio State University. Undergraduate Research Festival. 2018 Autumn. Poster Presentation.
Natural aqueous systems contain dissolved organic matter as well as colloidal mineral particles, and the interactions between them in different environmental conditions are important because results have wide-spread application in water treatment and filtration. Hematite nanoparticles exhibit a high level of stability and predictability, making them an ideal model to study the effect of organic acids on mineral surface charges and the subsequent effect on the aggregation kinetics of environmentally ubiquitous nanoparticles. The organic acids that were studied are citric acid and humic acid, sourced from the Suwannee River. I explored the effects of varying electrolyte concentrations on the aggregation kinetics of the hematite particles, tested with either a citric acid or humic acid coating in solutions of environmentally relevant pH’s. I started by measuring the aggregation kinetics of bare hematite at pH’s 4, 5, 6, 8, and 9. In each condition, the kinetics of bare hematite nanoparticles were measured by combining a hematite solution with varying concentrations of NaCl. After measuring the behavior of bare hematite nanoparticles, studies with ranging ionic strengths were conducted with a citric acid coating of either 1 g hematite/ 100 µmol citric acid or 1 g hematite/ 2000 µmol citric acid. After the data set using citric acid was complete, the effect of humic acid on hematite nanoparticles was conducted by using concentrations ranging from 0.1-0.5 mg/L humic acid to 100 mg/L. Measurements were made using the Dynamic Light Scattering (DLS) apparatus, which measures the effective diameter of solution particles as a function of time and indicates the aggregation of the solution over time. After each testing condition was tested, the data was analyzed to calculate the critical coagulation concentration (CCC). The CCC is the ionic strength of a solution at which when particles collide, coagulation will always occur. This research has expanded on knowledge regarding hematite behavior in aqueous settings and provides widespread applications in the design of wastewater treatment and filtration processes.
Academic Major: Environmental Engineering
National Science Foundation
OSU College of Engineering
OSU College of Engineering
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