Premium
Effect of pH and ionic strength on the electrical charge and particle size distribution of starch nanocrystal suspensions
Author(s) -
Romdhane Ahlem,
Aurousseau Marc,
Guillet Agnès,
Mauret Evelyne
Publication year - 2015
Publication title -
starch ‐ stärke
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.62
H-Index - 82
eISSN - 1521-379X
pISSN - 0038-9056
DOI - 10.1002/star.201400181
Subject(s) - zeta potential , ionic strength , chemistry , particle size , hydrolysis , surface charge , sulfuric acid , titration , suspension (topology) , aqueous solution , particle size distribution , inorganic chemistry , chemical engineering , nanoparticle , organic chemistry , mathematics , homotopy , pure mathematics , engineering
The current study investigates the amount of charged groups induced by sulfuric acid hydrolysis on the surface of starch nanocrystals. Conductometric titration revealed the existence of both weak and strong acidic groups. Strong acidic groups (sulfate ester groups) were present at low amounts (13.2 mmol kg −1 ) and their concentration increased with increasing duration of hydrolysis. The amounts of weak acidic groups (carboxylic acid) were greater (32–38 mmol kg −1 ) and the duration of hydrolysis appeared to have no effect. Negative zeta potential values were measured in the studied pH ranges (2.3 and 10). Zeta potential decreased for pH values fewer than 4, remained constant between 4 and 8, then decreased for higher values. Absolute zeta potential values were low (−6 to −29 mV) which could explain the poor suspension stability and the great tendency for particles to aggregate and settle in an aqueous medium. The increase in the pH of the suspension resulted in a lower aggregation as the mean apparent size of the particles decreased in this case. The increase in ionic strength had a similar effect, although the mechanisms involved were hypothesised to be quite different.