Search

In this study, chitosan-blended composites were synthesised from chitosan, kenaf fibre and γ-Fe2O3 nanoparticles. The chitosan-blended composites were used for the adsorption of chromium (VI) and sulphates from a potassium dichromate solution and an acid mine drainage (AMD) sample obtained from the CSIR, South Africa. Three chitosan-blended composites were synthesised namely CF(30) (Chitosan 70 and 30% kenaf fibre); CN20 (Chitosan 80 and 20% Fe2O3 nanoparticles) and CF(20)N(20) (Chitosan 60%, kenaf fibre 20% and 20% Fe2O3 nanoparticles). The adsorption of chromium (VI) on these three chitosan composites was compared with the adsorption on unmodified chitosan. The microstructure of chitosan and chitosan-blended composites was evaluated by SEM–EDS, XRD, FTIR and TGA. Batch experiments were carried out by varying the pH, temperature, adsorbent loading and contact time in order to optimise the conditions. The removal of chromium (VI) from the potassium dichromate solution was found to be optimal at 40 °C at a pH 2 when 1 g adsorbent was used. The composite CF(30) had the highest chromate ion ( Cr 2 O 7 2 - ) removal of ~ 70% at optimal conditions compared to the other prepared composites. The unmodified chitosan had a maximum chromate ion ( Cr 2 O 7 2 - ) removal of ~ 46% at optimal conditions. The unmodified chitosan and chitosan composites showed to follow a pseudo-second-order kinetic model, whereby adsorption of chromate ions was through chemisorption. The unmodified chitosan was found to remove ~ 98% of the chromium (VI) and ~ 70% sulphates, while the composite CF(20)N(20) had the highest removal compared to other chitosan-blended composites, with a removal of ~ 97% chromium (VI) and ~ 67% sulphate on AMD solution . Adsorption of chromium (VI) from AMD proved to be efficient since it is difficult to adsorb chromium (VI) at such a low concentration of 78 μg/L especially when sulphate concentration is at 21.82 g/L, whereby the adsorbent would had high affinity to adsorb sulphates instead of chromium (VI). [ABSTRACT FROM AUTHOR]

Kenaf and sisal fibres were selected for the development of natural fibre-reinforced thermoplastic composites because they are in abundance in South Africa. These materials can be used in the building industry, where good mechanical and fire resistance properties are required for structural and non-structural applications. High load bearing, moisture and fire can negatively affect the properties of these composites and decrease their performance. The effect of water glass, maleic anhydride-grafted-polypropylene (MAPP) treatment and fibre loadings on mechanical and thermal properties as well as fire resistance of kenaf and sisal fibre-reinforced polypropylene composites were investigated. The fibre-reinforced polypropylene composites were produced by injection and compression moulding processes. A significant improvement of the tensile strength and modulus of kenaf fibre composites was more pronounced when compared to sisal fibre composites. However, the water glass has a slight negative influence on mechanical properties of fibre/polypropylene matrix composites but showed better fire resistance and thermal properties when compared to the untreated fibre/polypropylene composites. Generally, the impact strength of fibre/polypropylene composites decreased with the addition of MAPP. The low impact strength could be the results of weak interfacial bond strength between the fibre and the matrix. The total heat release was reduced by water glass treatment due to the non-flammable polysilicate coating, while the average mass loss rate was slightly reduced by MAPP. [ABSTRACT FROM AUTHOR]

Abstract: Kenaf is an important fiber crop worldwide. It was recently introduced to South Africa as a commercial fiber crop. The aim of this study was to determine how different environments and seasons influence stalk yield. Nine kenaf cultivars from various countries were analysed in two environments, over two consecutive seasons, where one location was irrigated and the other not. Data were recorded for total fresh yield, defoliated stalk yield and dry stalk yield. Yield stability was analysed with four different statistical models. The dry stalk yield varied from 15.33 to 17.78ton/ha. El Salvador and Tainung 2 had high dry stalk yields in the favourable environments, but Tainung 2 did not have stable yield across all trials. Everglades 41 and El Salvador were the most stable of the varieties across both environments and seasons. El Salvador was the cultivar that had the highest and most stable dry stalk yield in the two seasons and two locations in South Africa, and should perform well in commercial production. [Copyright &y& Elsevier]

Examines the wilting of kenaf caused by Sclerotium rolfsii in South Africa. Tan lesions of stems at ground level; Pathogenicity of the fungus; Effect of the fungi on yield and fiber quality of kenaf.