What in particle morphology determines the DLVO interaction energy between hematite particles in electrolyte solutions?

The experimental stability of hematite particles (radius: similar to 74 nm) dispersed in solutions of varying salinity deviates considerably from predictions based on the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. For untreated hematite particles, at pH = 6 and 10, the theoretical values could be matched to the experimental ones by modifying the particle radius used in calculations from 74 to 13 nm. For particles heat-treated at 350 degrees C for 1 h, the theoretical values at pH = 10 could also be matched to the experimental ones by modifying the particle radius to 7 nm. Atomic force microscopy measurements revealed that the radius of curvature for surface protrusions on the hematite particles was 14 nm on average for the untreated particles at pH = 6 and 10, which almost equals the aforementioned modified particle radius. For the heat-treated hematite particles at pH = 10, the average radius of curvature was 9 nm, which also matched the corresponding modified particle radius. Therefore, we argue that the interaction energy between hematite particles is governed by not the overall particle radius but the curvature radius for surface protrusions. This could account for the discrepancy between theory and experiment regarding the salinity-dependent stability ratio of these particle dispersions.

Automated summary

The experimental stability of hematite particles in solutions with different salinity deviates from the predictions of the DLVO theory. Modifying the particle radius used in calculations can match the experimental values for untreated and heat-treated particles. Atomic force microscopy measurements reveal a correlation between the curvature radius of surface protrusions and the interaction energy between particles. This suggests that the stability ratio of these particle dispersions is governed by the curvature radius, not the overall particle radius.