Guidelines for potentiometric measurements in suspensions Part A. The suspension effect (IUPAC Technical Report)

Oman, S.; Camões, Maria Filomena; Powell, Kipton J.; Rajagopalan, Raj; Spitzer, Petra

doi:10.1351/pac200779010067

Cited by 24 publications

(17 citation statements)

References 17 publications

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“…• Complications in these measurements arise from the suspension effect [83][84][85][86]. In the present case, this will be neglected as is the case in all other studies of this kind that we are aware of.…”

Section: Surface Properties Of Well-defined Clay Samplesmentioning

confidence: 99%

Charging Behavior of Clays and Clay Minerals in Aqueous Electrolyte Solutions — Experimental Methods for Measuring the Charge and Interpreting the Results

Preočanin¹,

Abdelmonem²,

Montavon³

et al. 2016

Clays, Clay Minerals and Ceramic Materials Based on Clay Minerals

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We discuss the charging behavior of clays and clay minerals in aqueous electrolyte solutions. Clay platelets exhibit different charging mechanisms on the various surfaces they expose to the solution. Thus, the basal planes have a permanent charge that is typically considered to be independent of pH, whereas the edge surfaces exhibit the amphoteric behavior and pH-dependent charge that is typical of oxide minerals. Background electrolyte concentration and composition may affect these two different mechanisms of charging in different ways. To guide and to make use of these unique properties in technical application, it is necessary to understand the effects of the various master variables (i.e. pH and background salt composition and concentration). However, how to disentangle the various contributions to the charge that is macroscopically measurable via conventional approaches (i.e. electrokinetics, potentiometric titrations, etc.) remains a challenge. The problem is depicted by discussing in detail the literature data on kaolinite obtained with crystal face specificity. Some results from similar experiments on related substrates are also discussed. As an illustration of the complexity, we have carried out extensive potentiometric mass and electrolyte titrations on artificial clay samples (Na-, Ca-, and Mgmontmorillonite). A wide variety of salts was used, and it was found that the different electrolytes had different effects on the end point of mass titrations. In the case of a purified sample (i.e. no acid-base impurities), the end point of a mass titration (the plateau of pH achieved for the highest concentrations of solid), in principle, corresponds to the point of zero net proton and hydroxide consumption, at which in ideal systems, such as oxide minerals, the net proton surface charge density is zero. To such concentrated (dense) suspensions of clay particles, aliquots of salts can be added and the resulting pH indicates the specificity of a given salt for a given clay particle system. In the experimental data, some ambiguity remains, which calls for further detailed and comprehensive studies involving the application of all the available techniques to one system. Although, right now, the overall picture appears to be clear from a generic point of view (i.e. concerning the trends), clearly, in a quantitative sense, huge differences occur for nominally identical systems and only such a comprehensive study will allow to proof the current phenomenological picture and allow the next step to be taken to understand the fine details of the complex clay-electrolyte solution interfaces.

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Section: Surface Properties Of Well-defined Clay Samplesmentioning

confidence: 99%

Charging Behavior of Clays and Clay Minerals in Aqueous Electrolyte Solutions — Experimental Methods for Measuring the Charge and Interpreting the Results

Preočanin¹,

Abdelmonem²,

Montavon³

et al. 2016

Clays, Clay Minerals and Ceramic Materials Based on Clay Minerals

View full text Add to dashboard Cite

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“…The measurement of proton binding in concentrated suspensions at low ionic strength will be subject to artefacts from the ‘suspension effect of the first kind’ as defined by Oman et al (2007). This arises because the ion‐sensitive probe (the glass electrode in this case) experiences counterions associated with particulate and colloidal material as well as those in the bulk solution.…”

Section: Ion‐binding Modelsmentioning

confidence: 99%

Proton interactions with soil organic matter: the importance of aggregation and the weak acids of humin

Cooke

Tipping

Hamilton−Taylor

2008

European J Soil Science

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“…The suspension effect (IUPAC Technical Report)" [5], the operational definition of the SE at any temperature and pressure is:…”

Section: Recommendation For the Operational Definition Of The Suspensmentioning

confidence: 99%

“…Part A. The suspension effect (IUPAC Technical Report)" [5] regarding the origin and interpretation of the SE require modification of the definition of the SE.…”

Section: Introduction: Recommended Definition Of the Suspension Effecmentioning

confidence: 99%

Guidelines for potentiometric measurements in suspensions Part B. Guidelines for practical pH measurements in soil suspensions (IUPAC Recommendations 2006)

Oman

Camões

Powell

et al. 2007

Pure and Applied Chemistry

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The measured cell potentials for suspension potentiometric cells have been interpreted and explained by a detailed analysis of the schemes for these cells ["Guidelines for potentiometric measurements in suspensions. Part A. The suspension effect (IUPAC Technical Report", Pure Appl. Chem.79, 67 (2007)]. Some former disagreements amongst investigations have been clarified. A new unambiguous operational definition of the suspension effect (SE) is presented. It is defined as the difference in cell potential for two suspension potentiometric cells, one with both electrodes in the separated equilibrium solution (eqs) and the other with both electrodes in the sediment or suspension. This potential difference is the sum of the change in the indicator electrode (IE) potential and the change in the liquid junction potential of the reference electrode (RE), when the electrodes are used for measurement, once in the sediment of the suspension and then in its eqs.

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Guidelines for potentiometric measurements in suspensions Part A. The suspension effect (IUPAC Technical Report)

Cited by 24 publications

References 17 publications

Charging Behavior of Clays and Clay Minerals in Aqueous Electrolyte Solutions — Experimental Methods for Measuring the Charge and Interpreting the Results

Charging Behavior of Clays and Clay Minerals in Aqueous Electrolyte Solutions — Experimental Methods for Measuring the Charge and Interpreting the Results

Proton interactions with soil organic matter: the importance of aggregation and the weak acids of humin

Guidelines for potentiometric measurements in suspensions Part B. Guidelines for practical pH measurements in soil suspensions (IUPAC Recommendations 2006)

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