The consolidation of @entity3759 suspensions (anatase and rutile) due to gravity sedimentation in the presence of electrolytes has been investigated as a function of pH. @entity1372 and @entity70445 were used as flocculating electrolytes. The particle interaction was related to the zeta potential and the thickness of the electrical double layer, kappa(-1), by utilizing the repulsive barrier in the classical DLVO theory. The stability of the suspensions was represented as the average final solids content of the sediment cake, phi(fin). The batch sedimentation process was followed by scanning the sample cell with X-rays, from which the solids content and the particle size were calculated. Generally, dense sediments, with phi(fin) up to volume fractions of 0.5, were found for stable suspensions. Flocculated suspensions produced sediments with low phi(fin). The phi(fin) was observed to increase linearly with increasing repulsive barrier. However, at pH values only slightly higher than the isoelectric point (pH(iep)) the phi(fin) remained low until it returned to linearity at a pH much higher than pH(iep). This was attributed to the stronger affinity of @entity1372 than of @entity1507 for the particle surface, which may be explained by the higher negative hydration energy of @entity1372 . The stronger affinity of @entity1372 was also shown as unsymmetrical distribution of phi(fin) around pH(iep), with stronger flocculation at pH>pH(iep). The interpretation of phi(fin) as a function of the repulsive barrier (or kappa(-1)) also made it possible to distinguish between the adsorption mechanisms of ions from solution. Addition of electrolyte at a fixed low and high pH (surface positively and negatively charged, respectively) clearly showed the specificity in adsorption and consequent flocculation of the barium ion from the indifferent @entity1507 . @entity1372 was, however, again observed to flocculate the @entity3759 suspensions slightly more strongly than @entity1507 .

Consolidation behavior in sedimentation of XXXX suspensions in the presence of electrolytes.

@entity1372 :: ('MESH:D012964', 'Chemical') :: ['Sodium', 'sodium'] @entity3759 :: ('CHEBI:32234', 'Chemical') :: ['TiO(2)'] @entity70445 :: ('MESH:C023545', 'Chemical') :: ['barium nitrate'] @entity1507 :: ('CHEBI:48107', 'Chemical') :: ['nitrate']
@entity3759 :: (CHEBI:32234,Chemical) :: ['TiO(2)']
