Berlin 2024 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 28: Poster III

CPP 28.53: Poster

Mittwoch, 20. März 2024, 11:30–13:30, Poster C

Charge characterization of latex colloids under thoroughly deionized and decarbonized as well as under ambient CO₂ conditions — •Peter Vogel and Thomas Palberg — Johannes Gutenberg Universität, Mainz, Germany

We report on the charging behavior of dielectric colloidal particles bearing dissociable surface groups in salt-free aqueous environments in absence and presence of ambient CO₂. We performed systematic measurements of the low-frequency bulk conductivity in dependence on the particle number density and upon adding neutral electrolytes to determine both the effective and bare particle charges based on our conductivity model assuming independent migration of all ionic species present in solution. We find that upon equilibration with ambient CO₂ the effective number of freely mobile counterions decreases by about 50 %. As function of the electrolyte concentration, the measured conductivity reveals a pronounced difference in the curve shape depending on the presence of CO₂. Caused by the surface adsorption of molecular CO₂, we demonstrate the absence of micro-ionic exchange processes in-between the proposed inner and outer part of the electrical double layer as deviated from the strict linear increase in conductivity. Conversely, starting from the deionized and decarbonized state, we observe a pronounced non-linear behavior fully accounted for by our model assumptions.

Keywords: charged colloids; electrical double layer; conductivity; CO2 adsorption