Browsing by Author "Ngila, Jane C."

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    Controlling the release of wood extractives into water bodies by selecting suitable eucalyptus species
    (2012-12) Kilulya, Kessy; Msagati, Titus A. M.; Mamba, Bhekie B.; Ngila, Jane C.; Bush, Tamara
    Pulping industries are increasing worldwide as a result of the increase in the demand for pulp for cellulose derivatives and paper manufacturing. Due to the activities involved in pulping processes, different chemicals from raw materials (wood) and bleaching agents are released in pulp-mill effluent streams discharged into the environment and find their way into water bodies. Large quantities of water and chemicals used in pulping result in large amounts of wastewater with high concentrations of extractives such as unsaturated fatty acids, which are known to be toxic, and plant sterols which affect the development, growth and reproduction of aquatic organisms. This study was aimed at assessing the composition of extractives in two eucalyptus species used for pulp production in South Africa, in order to identify the suitable species with regard to extractive content. Samples from two eucalyptus plant species (Eucalyptus grandis and Eucalyptus dunnii) were collected from three sites and analysed for extractives by first extracting with water, followed by Soxhlet extraction using acetone. Compounds were identified and quantified using gas chromatography-mass spectrometry (GC-MS). Major classes of extractives identified were fatty acids (mainly hexadecanoic acid, 9,12-octadecadienoic, 9-octadecenoic and octadecanoic acids) and sterols (mainly β-sitosterol and stigmastanol). E. dunnii was found to contain higher amounts of the compounds compared to those found in E. grandis in all sampled sites. Principal component analysis (PCA) was performed and explained 92.9% of the total variation using three principal components. It was revealed that the percentage of fatty acids, which has a negative influence on both principal components 2 and 3, was responsible for the difference between the species. E. grandis, which was found to contain low amounts of extractives, was therefore found suitable for pulping with regard to minimal water usage and environment pollution.
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    Effect of site, species and tree size on the quantitative variation of lipophilic extractives in Eucalyptus woods used for pulping in South Africa
    (2014-04) Kilulya, Kessy; Msagati, Titus A. M.; Mamba, Bhekie B.; Ngila, Jane C.; Bush, Tamara
    Lipophilic wood extractives have serious negative impacts on both pulping process and quality of produced pulp. This study aimed at identifying suitable wood materials for pulping with respect to their lipophilic extractives contents. The effect of site, species and tree sizes on the amount of lipophilic extractives was evaluated. The lipophilic extractives from selected Eucalyptus species used for pulping in South Africa were quantified using gas chromatography–mass spectrometry. It was revealed by the use of analysis of covariance (ANCOVA) that the quantitative variation of lipophilic extractives in Eucalyptus woods is significantly affected by respective sites and tree species. Principal component analysis (PCA) revealed the correlation of the amount of lipophilic extractives in wood materials with tree species/clones and site soil composition. Thus, high amounts of lipophilic extractives were found in Eucalyptus trees grown at sites with a high composition of clay soil and organic matter. Whereas, Eucalyptus dunnii was found to contain a higher amount of lipophilic extractives than Eucalyptus grandis in all the sampled sites, implying an increased risk of pitch formation during the pulping process.
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    Evaluation of the influence of lipophilic extractive residues on dissolving pulp quality parameters by partial least squares method of chemometrics
    (2014-12) Kilulya, Kessy; Mamba, Bhekie B.; Ngila, Jane C.; Bush, Tamara; Msagati, Titus A. M.
    Dissolving pulp samples collected from the various pulping stages of the acid-bisulphite process were analysed for the lipophilic extractive residues as well as their effects and influence on the quality parameters of dissolving pulp were evaluated. The results obtained using the partial least squares (PLS) regression model showed that sterols, fatty alcohol, saturated and unsaturated fatty acids significantly influenced/affected the viscosity, Kappa number and carbohydrates in the pulp. The PLS model clearly separated the analysed pulp in terms of the species of the raw materials and pulping stages. Furthermore, it was observed that lipophilic extractives are negatively correlated to the yield of α-cellulose. Sterols, fatty acids and alcohols negatively influenced glucose in pulp, while xylose was found to be positively correlated to these components. Generally, the components of lipophilic extractives that have a major influence on the quality parameters were found to be sterols and saturated fatty acids.
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    Study of the Fate of Lipophilic Wood Extractives During Acid Sulphite Pulping Process by Ultrasonic Solid-Liquid Extraction and Gas Chromatography Mass Spectrometry
    (2012-06) Kilulya, Kessy; Msagati, Titus A. M.; Mamba, Bhekie B.; Ngila, Jane C.; Bush, Tamara
    Lipophilic extractives in dissolving pulp are still a big concern for pulp industries due to their detrimental effect on the quality of pulp. Since lipophilic extractives remaining in pulp are trapped in low-accessible fiber structures, effective extraction methods need to be established for studying their fate in the process. A simple, ultrasonic, solid liquid extraction established in this study was found to be more effective in capturing extractive residues in all “elemental chlorine-free” bleaching stages. Its efficiency was dependent on the extraction temperature, time, and solvent composition. A linearly correlated removal pattern of sterols and unsaturated fatty acids by the bleaching sequence was observed. It was further found that the bleaching combination did not fully remove lipophilic extractives. This study suggests an opportunity to explore ultrasonication-based extraction as an effective extraction procedure prior to gas chromatography mass spectrometry analysis for monitoring extractives in pulp.