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Patrick S. Nicholson – One of the best experts on this subject based on the ideXlab platform.

  • Influence of Acidity on the stability and rheological properties of ionically stabilized alumina suspensions in ethanol
    Journal of the American Ceramic Society, 2004
    Co-Authors: Gonghou Wang, Patrick S. Nicholson
    Abstract:

    The ionic stability of alumina particles in moderately concentrated ethanol suspensions is studied. Surface chemistry and interparticle forces are manipulated by controlling the Acidity of the suspensions without dispersants. The Acidity of ethanol solution is determined using ion transfer functions, wherein the relationships between Acidity, alumina particle surface charge, zeta-potential, stability, and suspension rheological behavior are established. Positive isoelectric point (IEP) shift is observed for alumina in ethanol on increasing the solids concentration. However, dilute and concentrated aqueous suspensions of alumina give the same IEP. The viscosity and flow curves for alumina/ethanol suspensions are Acidity dependent. The flow curves of the suspensions follow the Casson model, and the Casson yield value is used to evaluate suspension stability.

Gonghou Wang – One of the best experts on this subject based on the ideXlab platform.

  • Influence of Acidity on the stability and rheological properties of ionically stabilized alumina suspensions in ethanol
    Journal of the American Ceramic Society, 2004
    Co-Authors: Gonghou Wang, Patrick S. Nicholson
    Abstract:

    The ionic stability of alumina particles in moderately concentrated ethanol suspensions is studied. Surface chemistry and interparticle forces are manipulated by controlling the Acidity of the suspensions without dispersants. The Acidity of ethanol solution is determined using ion transfer functions, wherein the relationships between Acidity, alumina particle surface charge, zeta-potential, stability, and suspension rheological behavior are established. Positive isoelectric point (IEP) shift is observed for alumina in ethanol on increasing the solids concentration. However, dilute and concentrated aqueous suspensions of alumina give the same IEP. The viscosity and flow curves for alumina/ethanol suspensions are Acidity dependent. The flow curves of the suspensions follow the Casson model, and the Casson yield value is used to evaluate suspension stability.

Richard T Bush – One of the best experts on this subject based on the ideXlab platform.

  • Liberation of Acidity and arsenic from schwertmannite: Effect of fulvic acid
    Chemical Geology, 2014
    Co-Authors: Chamindra L. Vithana, Leigh A Sullivan, Edward D Burton, Richard T Bush
    Abstract:

    Abstract Schwertmannite is one of the major components that produces Acidity in acid mine drainage (AMD) and acid sulfate soils (ASS) and is also known to be an effective scavenger of Arsenic (As) in such environments. Fulvic acid (FA) is an active component of natural organic matter (NOM) and is known to interact strongly with both schwertmannite and As. Two main environmental hazards related to schwertmannite are Acidity liberation and potential re-mobilization of adsorbed or co-precipitated As upon hydrolysis. This study focused on understanding the behaviour of As-substituted schwertmannite with regard to the potential of Acidity liberation, the effect of FA on Acidity liberation from both pure and As-substituted synthetic schwertmannites, and the effect of FA on arsenic mobilization from As-substituted synthetic schwertmannite. This was investigated by means of short-term (48 h) titrations. The liberation of Acidity from As-substituted schwertmannite and the effect of FA were examined at two pH values (i.e. 4.5 and 6.5) typical for ASS environments. As-substituted schwertmannite liberated a greater amount of Acidity in comparison to pure schwertmannite at both pHs. Concentration of FA and pH each showed a strong influence on the liberation of Acidity from both pure and As-schwertmannite. At the acidic pH (4.5), FA inhibited Acidity liberation from schwertmannite. At the near neutral pH of 6.5, the concentration of FA played a critical role in affecting the liberation of Acidity from schwertmannite. The initial liberation of Acidity was enhanced from pure schwertmannite at pH 6.5 by low FA concentration (1 mg L− 1) and from As-schwertmannite by both low (1 mg L− 1) and moderate (10 mg L− 1) FA concentrations. Interestingly, higher FA concentrations (25 mg L− 1) inhibited Acidity liberation from both types of schwertmannite in comparison to the control (pure/As-schwertmannite titrated without added FA). FA enhanced the liberation of As from the As-schwertmannite at both pHs under oxidising conditions and the rate of As liberation was greater at the near neutral pH. The present study provides new insights on the effect of As-substitution on Acidity liberation from schwertmannite and the role of FA on: a) liberation of Acidity, and b) As mobilization, from schwertmannite.

  • Acidity fractions in acid sulfate soils and sediments: contributions of schwertmannite and jarosite
    Soil Research, 2013
    Co-Authors: Chamindra L. Vithana, Richard T Bush, Leigh A Sullivan, Edward D Burton
    Abstract:

    In Australia, the assessment of Acidity hazard in acid sulfate soils requires the estimation of operationally defined Acidity fractions such as actual Acidity, potential sulfidic Acidity, and retained Acidity. Acid–base accounting approaches in Australia use these Acidity fractions to estimate the net Acidity of acid sulfate soils materials. Retained Acidity is the Acidity stored in the secondary Fe/Al hydroxy sulfate minerals, such as jarosite, natrojarosite, schwertmannite, and basaluminite. Retained Acidity is usually measured as either net acid-soluble sulfur (SNAS) or residual acid soluble sulfur (SRAS). In the present study, contributions of schwertmannite and jarosite to the retained Acidity, actual Acidity, and potential sulfidic Acidity fractions were systematically evaluated using SNAS and SRAS techniques. The data show that schwertmannite contributed considerably to the actual Acidity fraction and that it does not contribute solely to the retained Acidity fraction as has been previously conceptualised. As a consequence, SNAS values greatly underestimated the schwertmannite content. For soil samples in which jarosite is the only mineral present, a better estimate of the added jarosite content can be obtained by using a correction factor of 2 to SNAS values to account for the observed 50–60% recovery. Further work on a broader range of jarosite samples is needed to determine whether this correction factor has broad applicability. The SRAS was unable to reliably quantify either the schwertmannite or the jarosite content and, therefore, is not suitable for quantification of the retained Acidity fraction. Potential sulfidic Acidity in acid sulfate soils is conceptually derived from reduced inorganic sulfur minerals and has been estimated by the peroxide oxidation approach, which is used to derive the SRAS values. However, both schwertmannite and jarosite contributed to the peroxide-oxidisable sulfur fraction, implying a major potential interference by those two minerals to the determination of potential sulfidic Acidity in acid sulfate soils through the peroxide oxidation approach.