Browsing by Author "Mezzalira, Melissa Giacomet"
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- Dry purification of ethanolic biodiesel through adsorption using almond shells based materialsPublication . Mezzalira, Melissa Giacomet; Queiroz, Ana Maria; Ribeiro, António; Brito, Paulo; Gomes, Maria Carolina SérgiThe growing demand for renewable energy sources has driven the development of sustainable alternatives to fossil fuels, among which biodiesel stands out. Biodiesel can be produced from various types of oils, including waste cooking oil (WCO), contributing to the sustainability of the process. An important step in its production process is purification, which is usually carried out through wet washing. Although effective, this method generates large volumes of effluent. Thus, the use of adsorbent materials emerges as a more sustainable alternative for removing impurities such as glycerol. Biodiesel was produced through a transesterification reaction using WCO with an oil:alcohol molar ratio of 1:7.5 and 0.5 wt% catalyst, resulting in a biodiesel with an ester yield of 83.5%. Three adsorbents were prepared from almond shell waste: the first was carbonized at 500°C for 1 hour, the second chemically activated using zinc chloride and the third chemically activated with phosphoric acid. After preliminary adsorption experiments, the adsorbent activated with phosphoric acid was selected for full characterization and further adsorption studies. Kinetic adsorption studies were carried out in batch mode at three different temperatures (25, 35, and 45°C), revealing that equilibrium was reached in approximately 2 hours, with a removal percentage of 73.4% at 25°C. Pseudo-first-order and pseudo-second-order models were fitted to the experimental data. Equilibrium studies were performed at the optimal temperature identified in the kinetics (25°C), and the Langmuir, Freundlich, and Sips models were adjusted to the experimental data, with the Sips model the one that best describe the adsorption behavior of the system. The highest glycerol removal was achieved using 10 wt% of the adsorbent, reaching a maximum of 81.1% removal and a minimum glycerol content of 0.041 wt%, which is still above the limit established by the EN14214:2012 standard. Continuous adsorption experiments were performed in a fixed-bed column, with adsorption–desorption cycles operated at flow rates below 1 mL/min. The highest adsorption capacity (41.64 mg/g) was observed at a flow rate of 0.68 mL/min. The adsorption/desorption cycles indicated the regeneration potential of the adsorbent. Finally, the effect of other contaminants in biodiesel on glycerol adsorption was evaluated using a glycerol solution in ethyl acetate. The results showed a reduction in adsorption capacity (31.55 mg/mL), possibly due to the faster adsorption process, which hindered the complete use of the column bed. When comparing batch and continuous modes, the continuous process generally showed higher adsorption capacities, reinforcing its potential for industrial applications.
- Dry purification of ethanolic biodiesel through adsorption using almond shells based materialsPublication . Mezzalira, Melissa Giacomet; Queiroz, Ana Maria; Ribeiro, António; Brito, Paulo; Gomes, Maria Carolina SérgiThe growing demand for renewable energy sources has driven the development of sustainable alternatives to fossil fuels, among which biodiesel stands out. Biodiesel can be produced from various types of oils, including waste cooking oil (WCO), contributing to the sustainability of the process. An important step in its production process is purification, which is usually carried out through wet washing. Although effective, this method generates large volumes of effluent. Thus, the use of adsorbent materials emerges as a more sustainable alternative for removing impurities such as glycerol. Biodiesel was produced through a transesterification reaction using WCO with an oil:alcohol molar ratio of 1:7.5 and 0.5 wt% catalyst, resulting in a biodiesel with an ester yield of 83.5%. Three adsorbents were prepared from almond shell waste: the first was carbonized at 500°C for 1 hour, the second chemically activated using zinc chloride and the third chemically activated with phosphoric acid. After preliminary adsorption experiments, the adsorbent activated with phosphoric acid was selected for full characterization and further adsorption studies. Kinetic adsorption studies were carried out in batch mode at three different temperatures (25, 35, and 45°C), revealing that equilibrium was reached in approximately 2 hours, with a removal percentage of 73.4% at 25°C. Pseudo-first-order and pseudo-second-order models were fitted to the experimental data. Equilibrium studies were performed at the optimal temperature identified in the kinetics (25°C), and the Langmuir, Freundlich, and Sips models were adjusted to the experimental data, with the Sips model the one that best describe the adsorption behavior of the system. The highest glycerol removal was achieved using 10 wt% of the adsorbent, reaching a maximum of 81.1% removal and a minimum glycerol content of 0.041 wt%, which is still above the limit established by the EN14214:2012 standard. Continuous adsorption experiments were performed in a fixed-bed column, with adsorption–desorption cycles operated at flow rates below 1 mL/min. The highest adsorption capacity (41.64 mg/g) was observed at a flow rate of 0.68 mL/min. The adsorption/desorption cycles indicated the regeneration potential of the adsorbent. Finally, the effect of other contaminants in biodiesel on glycerol adsorption was evaluated using a glycerol solution in ethyl acetate. The results showed a reduction in adsorption capacity (31.55 mg/mL), possibly due to the faster adsorption process, which hindered the complete use of the column bed. When comparing batch and continuous modes, the continuous process generally showed higher adsorption capacities, reinforcing its potential for industrial applications.