The particles’ preparation involved several steps of washing,
centrifugation and re-dispersion. In control samples, the pellet
was well redispersed. Particles containing 7.4 mM calcium formed
very cohesive pellets upon centrifugation, hard to re-disperse.
Higher concentrations showed more brittle pellets. Furthermore,
all particle dispersions containing added calcium were prone to
sedimentation during storage. Sedimentation was visible within
1 h for particles containing > 15.0 mM calcium, and was much less
pronounced for particles prepared with 7.4 mM calcium, which
took a few days to show clear signs of sedimentation. The presence
of calcium caused screening of the charges (van Aken & van Vliet,
2002), resulting in reduced repulsive interaction, thereby inducing
aggregation and sedimentation. On the contrary, control particles,
with no calcium, showed stability to sedimentation, due to electrostatic
repulsion (Sag˘lam et al., 2013).
The particles’ preparation involved several steps of washing,centrifugation and re-dispersion. In control samples, the pelletwas well redispersed. Particles containing 7.4 mM calcium formedvery cohesive pellets upon centrifugation, hard to re-disperse.Higher concentrations showed more brittle pellets. Furthermore,all particle dispersions containing added calcium were prone tosedimentation during storage. Sedimentation was visible within1 h for particles containing > 15.0 mM calcium, and was much lesspronounced for particles prepared with 7.4 mM calcium, whichtook a few days to show clear signs of sedimentation. The presenceof calcium caused screening of the charges (van Aken & van Vliet,2002), resulting in reduced repulsive interaction, thereby inducingaggregation and sedimentation. On the contrary, control particles,with no calcium, showed stability to sedimentation, due to electrostaticrepulsion (Sag˘lam et al., 2013).
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