Microstructure and rheology of bentonite slurries containing multiple-charge phosphate-based additives

Research output: Contribution to journalArticle

10 Citations (Scopus)


The multiple-charge phosphate-based additives affected the rheology of bentonite gels differently. The yield stress decreased with increasing concentration of additives. However for the triple-charge additives, PO4 3− and cyclic P3O9 3− the maximum extent of yield stress reduction was only about 50%. For the higher multiple-charge additives, P2O7 4−, P3O10 5− and (PO3 )17 the decrease was >95% where yield stress of <1 Pa was attained at high concentration. The cryo-SEM images of the bentonite gels under the influence of various phosphate additives showed similar microstructure as the untreated gels. An exception was that treated with 10 dwb% (NaPO3)17 where the microstructure showed evidence of structural collapse with more lying platelets facing up. A positive site per anion adsorption model for PO4 3− and the close proximity of charge sites was invoked to explain its poor performance in yield stress and viscosity reduction. The adsorption of PO4 3− on adjacent sites is not possible because of charge repulsion between the anions due their close proximity to explain the low adsorption. The number of positive sites per anion adsorption was larger for the higher multiple-charge additives such as 2 for P2O7 4− and 3 for P3O10 5− and a few more for the (PO3 )17 was responsible for their higher adsorption and this was responsible for the identical decreasing yield stress trend with additive concentration observed. The 6-member ring anion, P3O9 3−, adsorption is poor due to its low charge and bulky structure.

Original languageEnglish
Pages (from-to)120-128
Number of pages9
JournalApplied Clay Science
Publication statusPublished - 1 Mar 2019

Fingerprint Dive into the research topics of 'Microstructure and rheology of bentonite slurries containing multiple-charge phosphate-based additives'. Together they form a unique fingerprint.

Cite this