TY - JOUR
T1 - Influence of charge exchange in acidic aqueous and alcoholic titania dispersions on viscosity
AU - Rosenholm, Jarl B.
AU - Dahlsten, Per
N1 - Funding Information:
Academy of Finland (contract nr. 116466 ), Center of Excellence for Functional Materials (FunMat) and Graduate School of Materials Research (GSMR) are acknowledged for financial support.
Publisher Copyright:
© 2015 Elsevier B.V. All rights reserved.
PY - 2015/12/1
Y1 - 2015/12/1
N2 - Charging effects resulting from adsorption of acid, acid anions, and protons on titania (anatase) surfaces in anhydrous or mixed alcohol-water dispersions is summarized. The suddenly enhanced conductivity as compared to titania-free solutions has previously been modeled and explained as surface-induced electrolytic dissociation (SIED) of weak acids. This model and recently published results identifying concurrent surface-induced liquid (solvent) dissociation (SILD) are evaluated with experimentally determined conductivity and pH of solutions, zeta-potential of particles, and viscosity of dispersions. Titania (0-25 wt%)-alcohol (methanol, ethanol, and propanol) dispersions mixed with (0-100 wt%) water were acidified with oxalic, phosphoric, and sulfuric acids. It was found that the experimental results could in many cases be condensed to master curves representing extensive experimental results. These curves reveal that major properties of the systems appear within three concentration regions were different mechanisms (SILD, surface-induced liquid dissociation; SIAD, surface-induced acid dissociation) and charge rearrangement were found to be simultaneously active. In particular, zeta-potential - pH and viscosity - pH curves are in acidified non-polar solvents mirror images to those dependencies observed in aqueous dispersions to which hydroxyl is added. The results suggest that multiple dispersion and adsorption equilibria should be considered in order to characterize the presented exceptionally extensive and complex experimental results.
AB - Charging effects resulting from adsorption of acid, acid anions, and protons on titania (anatase) surfaces in anhydrous or mixed alcohol-water dispersions is summarized. The suddenly enhanced conductivity as compared to titania-free solutions has previously been modeled and explained as surface-induced electrolytic dissociation (SIED) of weak acids. This model and recently published results identifying concurrent surface-induced liquid (solvent) dissociation (SILD) are evaluated with experimentally determined conductivity and pH of solutions, zeta-potential of particles, and viscosity of dispersions. Titania (0-25 wt%)-alcohol (methanol, ethanol, and propanol) dispersions mixed with (0-100 wt%) water were acidified with oxalic, phosphoric, and sulfuric acids. It was found that the experimental results could in many cases be condensed to master curves representing extensive experimental results. These curves reveal that major properties of the systems appear within three concentration regions were different mechanisms (SILD, surface-induced liquid dissociation; SIAD, surface-induced acid dissociation) and charge rearrangement were found to be simultaneously active. In particular, zeta-potential - pH and viscosity - pH curves are in acidified non-polar solvents mirror images to those dependencies observed in aqueous dispersions to which hydroxyl is added. The results suggest that multiple dispersion and adsorption equilibria should be considered in order to characterize the presented exceptionally extensive and complex experimental results.
KW - Charge exchange
KW - Dispersion stability
KW - Solvent/acid adsorption
KW - Solvent/acid dissociation
KW - Surface-induced dissociation (SIED, SILD, SIAD)
UR - http://www.scopus.com/inward/record.url?scp=84949504741&partnerID=8YFLogxK
U2 - 10.1016/j.cis.2015.10.007
DO - 10.1016/j.cis.2015.10.007
M3 - Review Article or Literature Review
AN - SCOPUS:84949504741
SN - 0001-8686
VL - 226
SP - 138
EP - 165
JO - Advances in Colloid and Interface Science
JF - Advances in Colloid and Interface Science
ER -