School of Chemical and Metallurgical Engineering

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Browsing School of Chemical and Metallurgical Engineering by Author "van Dyk, L."

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    Critical evaluation of the chemical composition of acid mine drainage for the development of statistical correlations linking electrical conductivity with acid mine drainage concentrations
    (Elsevier, 2022-05-06) Smith, J.; Sheridan, C.; van Dyk, L.; Harding, K.G.
    The design an effective treatment processes for the remediation of acid mine drainage (AMD) requires an understanding of the composition of the AMD water. The pH and elemental composition of AMD waters are site specific and are dependent on the regional geology, and environmental factors. To establish the chemical and physical characteristics of two AMD sites located in the Mpumalanga coal mining region, South Africa, samples were taken between February 2018 to April 2019. These data were compared against regulatory legislation, and the potential health effects of exposure indicated. Strong correlations were noted between parameters and statistical evaluation demonstrated that electrical conductivity (EC) could be a useful correlative for prediction of total acidity, dissolved iron, and sulfur concentrations in acidic AMD waters. From these findings, empirical correlations were used to derive regression equations which were used to derive the EC values corresponding to the respective water quality limits for TDS, dissolved iron, and sulfur to provide a rapid method for testing compliance. Given the site specificity of AMD composition, this approach is intended as a proof of concept for the development of a methodology for adaption at other AMD sites. The regression equations should not be considered as universal to all AMD sites and EC should also not be used as a replacement for more complete chemical analysis.
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    Modelling of Low Temperature Dilute Sulfuric Acid Pre-treatment of South African Grass
    (Elsevier, 2018-12-01) Burman, N.W.; Sheridan, C.; van Dyk, L.; Harding, K.G.
    Dilute acid hydrolysis is an effective method of pre-treatment of lignocellulosic biomass. Although there are many studies modelling this pre-treatment at high temperature (120–210 °C), no studies were found modelling this reaction at low temperature. In this study, a long grass species was pre-treated with dilute sulfuric acid (pH 1, 2 & 3) at low temperatures (35 °C, 65 °C, 90 °C). The hydrolysis of xylan was found to obey a bi-phasic model in which there are two fractions of xylan, with significantly different hydrolysis rates. The rates of hydrolysis of the fast reacting fraction was found to obey Arrhenius type temperature dependence (Ea = 155.06 kJ/mol, A0 = 1.65 × 1019/min), which agrees with findings of similar studies at higher temperatures. A negligible rate of hydrolysis was determined for the slow fraction which differs from previous studies. The proportion of the slow reacting fraction (50%) which is lower than previously determined (55%–100%).