CHEMICAL AND THERMAL STABILITY OF RICE HUSKS AGAINST ALKALI TREATMENT

Chemical and thermal stability of rice husks against alkali treatment with 2 to 8% w/v NaOH are presented and discussed in this paper. The thermal stability of the rice husks was examined by using a thermal gravimetric analysis instrument. Chemical stability was evaluated by examining the organic components of rice husks using proximate analysis. The results indicated that the proportion of lignin and hemicellulose in rice husks treated with NaOH ranging from 4 to 8% decreased significantly by 96% and 74%, respectively. The thermal stability and final degradation temperatures of the alkali-treated rice husks were also lowered by 24-26°C due to degradation of hemicellulose and lignin during alkali treatment. Absence of the onset degradation zones in the alkali-treated rice husks was a further indication that hemicellulose and other volatile substances degraded during alkali treatment. This leads to a conclusion that alkali treatment of rice husks with more than 4% NaOH causes a substantial chemical degradation of rice husks, which subsequently decreases their thermal stability

Biocomposites of different lignocellulosic wastes for sustainable food packaging applications

The suitability of three local lignocellulosic wastes i.e. almond shell (AS), rice husk (RH) and seagrass (SG) as fillers in PHB/Fiber composites applications has been studied. PHB/Fiber composites with 10 phr and 20 phr fiber content were prepared by melt blending. The influence of the fiber type (size, morphology and origin) and content on the morphological, mechanical and thermal properties of the as obtained composites has been assessed. To evaluate the potential use in food packaging applications, the barrier performance to water, thermoforming ability and disintegration in controlled composting conditions of the composites were also studied. All the fibers have demonstrated to be apt for their use as fillers in PHB/Fiber composites, showing a reinforcing effect without affecting the crystallinity and the disintegration rate of PHB. The thermal stability and the water barrier performance of the composites were reduced by the presence of the fibers. Nevertheless, the addition of AS resulted in the best balance of properties, in terms of permeability and mechanical properties, finding an enhancement of the thermoforming ability of PHB when 10 phr of AS was added

Single solvent based film casting method for the production of porous polymer films

A single solvent based film casting process for fabricating porous polymer films was developed in this study. The porous film was produced by mixing concentrated polylactic acid/ chloroform solution (20 wt%) and fresh chloroform solvent followed by film casting. The average pore sizes of the films produced were seen to increase from 2.1 (±0.1) µm to 6.4 (±0.2) µm with increasing ratio of concentrated PLA solution and fresh solvent from 1:2 to 1:4. Functional groups of PLA after casting into porous film were confirmed via Fourier transform infrared (FTIR) spectroscopy analysis. Cytocompatibility studies (via Alamar Blue assessment) utilising MG-63 cells on the porous PLA films revealed an increase in cell metabolic activity up to 8 days post-seeding. In addition, these direct cell culture studies showed that the porous membranes supported cell adhesion and growth not only on the surface but also through the porous structures of the membrane, highlighting the suitability of these porous films in tissue engineering applications

Properties of composite panels from modified rice hulls

In this paper, the internal bond (LB.) strength, flexural properties, and thickness swelling ( TS) of composite panels produced ji'om hammer-milled amI steam pre-treate{l rice hulls bonded with phenol formaldehyde (PF) resin are presellled. Steam pre-treatment of the rice hull was carried out between 110 and 140°C, The LB. strellgth, flexural properties and TS of the resulting composite panels improved with steam pre-treatment of rice hulls. The highest mechanical properties and the lowest TS of the composite pallels were obtained from steam pre-treated rice hulls. Partial removal of surface impurities 011 the steam pre-treated rice hulls was  partly respollsible for the improved properties. Further improvement observed after illcrease{l the dellsity from 1000 to 1400 kgm-3 was  associated with enhanced interfacial billding stresses behveell the rice hull particles alld the PF resill. The LB. strellgth, flexural properties, and TS of the densified panels passed the requiremellts of EN 312-2 by 53%.Keywords: Composite pallels, illterface, mechallical testillg, thicklless swelling testing, steam pre-treatment

Use of tritium and stable water isotopes to assess contaminant transport at a burial site in Middelburg, Mpumalanga

When different water resource components coexist in nature, they usually have an impact on each other. Studies of how they impact each other in terms of water quantities, flow dynamics, quality and contamination are therefore necessary to ensure an appropriate water and environmental management is conducted. A study in Middleburg comprised a literature review and field investigations at and around a cemetery, as part of a Water Research Commission project on impacts on the water resource from large-scale burials. A literature review conducted has enabled familiarisation with similar studies that have been conducted around the subject. Reliable methodologies have therefore been adopted from the published literature and applied on the current research. A seasonal wetland is located downgradient of the cemetery, between the cemetery and a stream that flows past the cemetery. In order to assess possible flow pathways of near-surface and groundwater from the cemetery to the stream, monthly monitoring of surface and groundwater quality and level fluctuations was carried out on the stream, as well as existing and newly installed boreholes at the cemetery. Water samples collected were analysed for inorganic constituents, tritium, and stable water isotopes. The tritium and stable water isotope results – revealed the comparative influence of rainfall and shallow groundwater contributions to streamflow, while groundwater provides base-flows as the stream levels recede. The depth to groundwater reduced with increasing rainfall, indicating direct recharge. The difference in concentrations of some inorganic parameters in the stream compared to the groundwater at the cemetery revealed the effect of natural attenuation in the vadose zone due to reduced conditions and the wetland acting as a filter to improve the water quality of the shallow interflow on reaching the stream. Since isotope data indicated to be a useful tool in studying water resource interactions, the methodology should form part of site investigations for cemetery development or on existing cemeteries to study the current impact and/or predict future impacts that the cemetery may have on the water resources. The methodology best applies in areas with multiple water resources, where there may be an interconnection between them. The isotope studies can also be used to estimate recharge and thus contaminant transport rate of the cemetery leachate.Dissertation (MSc)--University of Pretoria, 2020.GeologyMScUnrestricte

Properties of Rice Husk Particle Boards Bonded by a Blend of Tannin-CNSL Resin

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