Relevance of Colloid Inherent Salt Estimated by Surface Complexation Modeling of Surface Charge Densities for Different Silica Colloids

Potentiometric titrations have been routinely used to measure the proton-related surface charge density (SCD) of particles in solution. Here, we quantify the SCD of silica nanoparticles (NPs) that are commercially available as charge-stabilized colloids (by the addition of NaOH) in the presence of k...

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Main Authors: Alok Goel, Johannes Lützenkirchen
Format: Article
Language:English
Published: MDPI AG 2022-04-01
Series:Colloids and Interfaces
Subjects:
Online Access:https://www.mdpi.com/2504-5377/6/2/23
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author Alok Goel
Johannes Lützenkirchen
author_facet Alok Goel
Johannes Lützenkirchen
author_sort Alok Goel
collection DOAJ
description Potentiometric titrations have been routinely used to measure the proton-related surface charge density (SCD) of particles in solution. Here, we quantify the SCD of silica nanoparticles (NPs) that are commercially available as charge-stabilized colloids (by the addition of NaOH) in the presence of known amounts of added NaCl. The experimental results are simulated by surface complexation models (SCMs) of the electrical double layer (EDL). The modeling results suggest that involving only the added NaCl electrolyte yields poor agreement between the experiment and the best achievable fit. An increase in the Na concentration accounting for the colloid inherent salt (CIS) associated with these charge-stabilized colloids results in much better simulations. In the available literature, this CIS has often been disregarded. However, in the modeling, the total concentration of Na must be known for a consistent mole balance and derivation of reliable ion-pair binding constants. If the CIS is not accounted for or the original suspensions are not dialyzed, the presence of CIS renders the study of those colloids difficult, particularly when investigating specific ion effects, since the CIS always interferes. In the present work, we show that the SCM-estimated amount of CIS from varying the total salt and solid concentration agrees surprisingly well with the manufacturer specification.
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spelling doaj.art-879c647e3aaa4659a15a0be222fec3522023-11-23T16:09:10ZengMDPI AGColloids and Interfaces2504-53772022-04-01622310.3390/colloids6020023Relevance of Colloid Inherent Salt Estimated by Surface Complexation Modeling of Surface Charge Densities for Different Silica ColloidsAlok Goel0Johannes Lützenkirchen1Laboratory for Surface Science and Technology, Department of Materials, ETH Zürich, 8093 Zurich, SwitzerlandInstitute for Nuclear Waste Disposal (INE), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen, 76344 Karlsruhe, GermanyPotentiometric titrations have been routinely used to measure the proton-related surface charge density (SCD) of particles in solution. Here, we quantify the SCD of silica nanoparticles (NPs) that are commercially available as charge-stabilized colloids (by the addition of NaOH) in the presence of known amounts of added NaCl. The experimental results are simulated by surface complexation models (SCMs) of the electrical double layer (EDL). The modeling results suggest that involving only the added NaCl electrolyte yields poor agreement between the experiment and the best achievable fit. An increase in the Na concentration accounting for the colloid inherent salt (CIS) associated with these charge-stabilized colloids results in much better simulations. In the available literature, this CIS has often been disregarded. However, in the modeling, the total concentration of Na must be known for a consistent mole balance and derivation of reliable ion-pair binding constants. If the CIS is not accounted for or the original suspensions are not dialyzed, the presence of CIS renders the study of those colloids difficult, particularly when investigating specific ion effects, since the CIS always interferes. In the present work, we show that the SCM-estimated amount of CIS from varying the total salt and solid concentration agrees surprisingly well with the manufacturer specification.https://www.mdpi.com/2504-5377/6/2/23silicapotentiometric titrationsurface charge densitycolloid inherent saltspecific ion effects
spellingShingle Alok Goel
Johannes Lützenkirchen
Relevance of Colloid Inherent Salt Estimated by Surface Complexation Modeling of Surface Charge Densities for Different Silica Colloids
Colloids and Interfaces
silica
potentiometric titration
surface charge density
colloid inherent salt
specific ion effects
title Relevance of Colloid Inherent Salt Estimated by Surface Complexation Modeling of Surface Charge Densities for Different Silica Colloids
title_full Relevance of Colloid Inherent Salt Estimated by Surface Complexation Modeling of Surface Charge Densities for Different Silica Colloids
title_fullStr Relevance of Colloid Inherent Salt Estimated by Surface Complexation Modeling of Surface Charge Densities for Different Silica Colloids
title_full_unstemmed Relevance of Colloid Inherent Salt Estimated by Surface Complexation Modeling of Surface Charge Densities for Different Silica Colloids
title_short Relevance of Colloid Inherent Salt Estimated by Surface Complexation Modeling of Surface Charge Densities for Different Silica Colloids
title_sort relevance of colloid inherent salt estimated by surface complexation modeling of surface charge densities for different silica colloids
topic silica
potentiometric titration
surface charge density
colloid inherent salt
specific ion effects
url https://www.mdpi.com/2504-5377/6/2/23
work_keys_str_mv AT alokgoel relevanceofcolloidinherentsaltestimatedbysurfacecomplexationmodelingofsurfacechargedensitiesfordifferentsilicacolloids
AT johanneslutzenkirchen relevanceofcolloidinherentsaltestimatedbysurfacecomplexationmodelingofsurfacechargedensitiesfordifferentsilicacolloids