Project Team
Students
Adam Levedakis
Materials Science and Engineering
Penn State Harrisburg
Faculty Mentors
James Adair
Penn State University Park
Materials Science and Engineering
Project
https://sites.psu.edu/mcreu/files/formidable/2/AAL-REU-Poster-2-.pdf
Project Video
Project Abstract
Name: Adam Levedakis
Campus Affiliation: Penn State Harrisburg
Materials Science and Engineering
Anticipated Graduation Date: May 2025
Mentors: James Adair (Penn State University Park)
Effect of pH on Size and Zeta Potential of Coal-Water Solutions
Aggregation is the premier obstacle in colloidal science, causing poorly dispersed suspensions. Aggregation occurs when particles form clusters leading to larger particles due to intermolecular van der Waals attractive interactions. Preventing aggregation in coal-water suspensions is the main goal of this research. Aggregation can be prevented by influencing zeta potential (ZP), the electric potential near the surface of the coal granules. The research investigated size and zeta potential of coal-water solutions as a function of suspension pH values. Coal-water solutions at various pH values were created using acid-base titration. The size and zeta potential were measured using dynamic light scattering (DLS) and electrophoretic light scattering (ELS), respectively. The determinations showed that the mean hydrodynamic diameter was smallest at more alkaline pH values and lower at more acidic suspension pH values. The zeta potential measurements were consistent with particle size with more alkaline providing higher magnitude ZP and more acidic values presenting smaller ZP magnitude. In high pH conditions the coal particles had the most negative zeta potential in contrast to less negative at more acidic conditions. The zeta potential and particle sizes are consistent with larger aggregates at low pH values and low ZP compared to high pH values and larger ZP dispersing the coal particles by repulsive electrostatic energies. This, the most colloidally stable coal-water suspensions are found in alkaline conditions. These findings are important because of the impact on current and future coal research to extract useful materials from coal including graphene.
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