1. What is DLVO theory?
2. What is the van der Waals force? How to calculate the van der Waals force between two spherical objects?
3. What is the electrostatic double layer force? Is it the same as the direct electrostatic interaction between charged objects? Why? What is Debye length? List as many methods to decrease electrostatic double layer force. How to calculate electrostatic double layer force between two spherical objects?
4. Calculate the total interaction between a chalcopyrite spherical particle and a bubble in water at different electrolyte concentrations (NaCl: 1x10¯⁴M, 1X10¯³M, 1x10¯²M). Plot Ftotal/R vs. Separation H (nm) using EXCEL or other software.
Known: Radius of chalcopyrite particle=20 µm; Radius of bubble=2mm; Ψbubble=-50mv;Ψbubble=-60mv;
Hints: van der Waals force does not change with electrolyte concentrations; Bubble is too big for a solid particle; therefore, it can be treated as a plate.
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(1) The DLVO theory explains the aggregation of aqueous dispersions quantitatively and describes the force between charged surfaces interacting through a liquid medium. It combines the effects of the van der Waals interaction and the electrostatic repulsion due to the so-called double layer of counter ions....
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