The present study indicates that solid acid catalysis of crude tall oil (CTO) over a WO3/ZrO2 catalyst is effective in converting the CTO fatty acids components into biodiesel in high yield. Preparation of the catalyst by an impregnation method was selected and WO3 activity was best at a loading mass fraction of 5% to ZrO2 support and activation at 500°C for five hours under air at atmospheric pressure. Optimal reaction conditions were reaction temperature at 250°C; methanol to CTO molar ratio at 10; reaction time four hours, catalyst mass fraction of 3%; and stirring intensity at 625 rpm. The conversion at optimal reaction conditions was 70%. The catalyst was highly active at temperatures higher than 200°C. The biodiesel produced met some, but not all, the diesel quality parameters stipulated by standard specifications such as ASTM D6751 and EN14214.
The search for a novel microbial producer of cellulases including a glucose tolerant β-glucosidase is a challenge as most are inhibited by their product glucose. This study aims to screen for cellulolytic fungi using qualitative and quantitative screening methods. Primary screening revealed 34 of 46 fungal isolates with β-glucosidase activity. Eleven and 13 of these also displayed endoglucanase and exoglucanase activities, respectively. During secondary screening, this number was reduced to 26 β-glucosidase producers with 13 also having endoglucanase and exoglucanase activities. Isolate C1 displayed enhanced production of β-glucosidases in the presence of 0.05 M glucose (69% higher activity). Optimisation of growth conditions for β-glucosidase production by one variable at a time experiments improved production for (isolates) PS1 (64%), MB5 (84%), and C2 (69%). Isolate PS1 identified as Chaetomella sp. BBA70074 displayed the highest tolerance to glucose, retaining 10% of β-glucosidase activity in the presence of 0.8 M glucose. Tolerance to glucose increased to 14% when produced under optimal conditions. β-Glucosidase had a molecular weight of 170 kDa with a pH and temperature optima of 6 and 70°C, respectively. Future studies will include optimisation of the production of the glucose tolerant enzyme by Chaetomella sp. BBA70074.
Abstract The pursuit for sustainability in the papermaking industry calls for the elimination or reduction of synthetic additives and the exploration of renewable and biodegradable alternatives. Cellulose nanofibrils (CNFs), due to their inherent morphological and biochemical properties, are an excellent alternative to synthetic additives. These properties enable CNFs to improve the mechanical, functional and barrier properties of different types of paper. The nanosize diameter, micrometre length, semi-crystalline structure, high strength and modulus of CNFs has a direct influence on the mechanical properties of paper such as tensile index, burst index, Scott index, breaking length, tear index, Z-strength, E-modulus, strain at break, and tensile stiffness. This review details the role played by CNFs as an additive to improve strength properties of papers and the factors affecting the improvement in paper quality when CNFs are added as additives. The paper also includes techno-economic aspects of the process and identifies areas that need further research.
Bleached hardwood and softwood South African kraft pulps were passed through a commercially available micro grinder for varying number of passes and the properties of the resultant pulps were assessed periodically using microscopy, Fourier transform infrared spectroscopy (FTIR), X-ray crystallography (XRD) and Thermogravimetric analysis (TGA).The ultrastructural analysis of the pulp fibres revealed that after 120 passes both hardwood and softwood bleached fibres showed the presence of cellulose nanofibres (CNFs).The FTIR analysis showed no modification to the cellulose structure and side groups upon treatment with the supermasscolloider (SMC).Both hardwood and softwood pulp fibres showed a decline in crystallinity after SMC treatment.For the hardwood pulps there were no major differences between the untreated pulps and those passed through the SMC.In the case of the softwood pulps, the SMC treatment resulted in more thermally stable CNFs compared with the untreated bleached pulps.This was observed at several levels of treatment (40, 120 and 200 passes).After 200 passes both the hardwood and softwood kraft pulp fibres produced CNFs with an average width of 11 nm and lengths with several micrometers.
The fast fashion trends in the textile industry have resulted in high consumption of fiber with concomitant generation of waste. Awareness of environmental pollution resulting from textile production and disposal has increased significantly. This increase has pushed research activities toward more sustainable recycling alternatives to properly handle the end-of-life of textiles. This review provides an overview of existing technologies, the latest developments, and research studies on the recycling technologies employed in the textile industry. Different types of recycling—mechanical, chemical, and biochemical recycling of standard fabrics used in garments, cotton, wool, polyester, polyamide 6 6, and acrylic—are explored. Recent advances in recycling technologies such as advanced sorting techniques, innovative chemical processing, and emerging biochemical processes are revealed. The review also highlights efforts being made by various agencies and companies in facilitating and employing the technologies on a commercial scale. Various methods for efficient textile waste sorting and identification are also discussed. The reviewed studies revealed that most recycling technologies were conducted on post-industrial textile waste, which tends to be homogenous in the types of dyes and fibers present in the waste. It also suggested that post-consumer textiles could be recycled using chemical and biological options that have the potential to valorize the waste into high-value products.
The South African pulp and paper industry generates an estimated 0.5 million tons of pulp and paper mill sludge (PPMS) annually. As PPMS is generated, it requires safe, efficient, and economical collection and disposal. However, PPMS is typically land-filled and subsequently emits nuisance odors, methane, and leaches toxins. Thus, PPMS is an environmental hazard and a potential pollutant of air, soil, and water systems. PPMS is primarily composed of cellulose and coupled with the prospect of biorefinery practices, a value-added product such as glucose-rich hydrolyzate can be derived from this lignocellulosic waste stream. The current study applied a Box-Behnken design to establish the appropriate conditions to obtain the highest possible yield of glucose from PPMS. The PPMS contained 6.89% ash and 64.21% cellulose. De-ashing using acidic pretreatment reduced the ash content by 51%, thereby increasing the amenability of the cellulose fibers to enzymatic hydrolysis. The optimized conditions for the model from the Box-Behnken design were: pH 4.89, 51 °C, hydrolysis time 22.9 h, 30 U/g β-glucosidase, and 60 U/g cellulase, and a substrate load of 6.4%. The model was validated using these conditions, and recovery of 0.48 g glucose per 1 g of fiber was attained. The hydrolyzate contained trace amounts of xylose and mannose. Pyrolysis gas chromatography-mass spectrometry elucidated that the hydrolyzate also contained low concentrations of toxins such as hemicellulose-derived acetic acid (0.25%), sugar-derived furans (1.06%), and lignin-derived phenols (0.58%). This study proposes a scheme that resulted in a 75% yield of glucose and validated the use of PPMS as a viable candidate for enzymatic saccharification. The glucose-rich hydrolyzate retrieved has potential capability as an inexpensive source of fermentable sugars in downstream applications.
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