| 1. |
- Hellsing, Maja S., et al.
(författare)
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Structure of flocs of latex particles formed by addition of protein from Moringa seeds
- 2014
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 460, s. 460-467
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Tidskriftsartikel (refereegranskat)abstract
- Proteins extracted from the seeds of Moringa trees are effective flocculents for particles dispersed in water and are attractive as a natural and sustainable product for use in water purification. Studies with a model system consisting of polystyrene latex particles have shown that the protein adsorbs to the surface and causes flocculation as unusually dense aggregates. Small-angle neutron scattering that exploits contrast matching of deuterated latex particles dispersed in D2O to highlight bound protein has shown that the adsorbed amount reaches about 3 mg m(-2). The particles form very compact flocs that are characterized by fractal dimensions that approach the theoretical maximum of 3. Ultra small-angle neutron scattering allows these flocs to be characterized for a range of particle and protein concentrations. Proteins from two species of Moringa trees were investigated. The protein from Moringa stenopetala seeds gave rise to slightly lower fractal dimensions compared to Moringa oleifera, but still much larger than values observed for conventional ionic or polymeric flocculents that are in the range 1.75-2.3. Compact flocs are desirable for efficient separation of impurities and dewatering of sludge as well as other applications. A trend of increasing fractal dimension with particle concentration was observed when M. stenopetala seed protein was used and this resembles the behaviour predicted in Brownian dynamics simulation of flocculation. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.
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| 2. |
- Nermark, Fiona M., et al.
(författare)
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Desulfurization of Morupule Coal with Subcritical Aqueous Ethanol Extraction
- 2022
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Ingår i: ChemistryOpen. - : Wiley. - 2191-1363. ; 11:11
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Tidskriftsartikel (refereegranskat)abstract
- Coal combustion greatly contributes to global emissions of toxic gases into the atmosphere, with sulfur emissions as one of the prominent pollutants in addition to carbon dioxide. Nevertheless, Botswana utilizes Morupule's sub-bituminous coal with average sulfur and ash contents, as determined in this study being 1.9 and 24.4 % by weight with an average calorific value of 22 MJ Kg−1 to generate electricity. We report an optimized extraction method for reducing total sulfur in Morupule coal from 1.9±0.2 to 0.43±0.02 wt.% at optimum conditions of ethanol/water (90/10, v/v %) at 129 °C (105 bars) in 10 minutes. A Box–Behnken experimental design was employed to select the optimal conditions of temperature (100–180 °C), water proportion in ethanol (10–90, v/v %) and extraction time (10–30 minutes), thus reducing the total sulfur under these mild conditions compared to conventional extraction. The optimized conditions were however not efficient in removing ash.
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| 3. |
- Nermark, Fiona M., et al.
(författare)
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Optimization of coal desulfurization method by sub/supercritical fluid extraction with binary mixtures of carbon dioxide and ethyl lactate as a solvent
- 2024
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Ingår i: Green Analytical Chemistry. - 2772-5774. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Coal combustion for energy results in the emission of air pollutants such as NOx and SOx, which negatively affect human health and the environment. Reducing toxic gas emissions and ash production is needed to achieve cleaner coal. This study aimed to develop an extraction method for desulfurizing coal with non-toxic solvents before combustion. Mixtures of sub/supercritical carbon dioxide and ethyl lactate (EL) were used at temperatures of 60–80 °C and extraction times of 15–45 min. Box-Behnken design (BBD) was used to assess the influence of the extraction parameters and to optimize the extraction method. The results show that higher temperatures and lower EL content significantly increased desulfurization. The optimal conditions for desulfurization were CO2/EL (95:5, v/v) at 80 °C, 300 bar and 15 min, reducing total sulfur in coal from 1.90 to 0.13% by weight. The extraction was efficient for removing organic sulfur, sulfones and sulfates, whereas there were still traces of sulfoxides and sulfides remaining in the coal after extraction. Moreover, the ash content slightly decreased while the calorific value increased by 8% and 3% by weight, respectively. The use of a temperature less than 100 °C and an extraction time of 15 min make this method "greener" in comparison to other proposed "green" methods, which use temperatures above 200 °C. Thus, the method has the potential to produce clean coal.
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