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The use of vegetable oils to produce biodiesel raises several sustainability issues, namely the fuel/food conflict. The high cost of vegetable oils and an expensive homogeneous base catalyzed process encourages the search for alternative raw materials and more efficient production processes. Biodiesel from beef tallow, a non-edible fat, was produced by methanolysis over calcium based heterogeneous catalyst. The catalyst was prepared by calcination of scallop shells at 800 ​°C. To overcome the undesired effect of the tallow acidity (3.9 mgKOH/gfat), mixtures of tallow and soybean oil (SBO) (0.6 mgKOH/gfat) were processed and alcohol co-solvents (isopropanol, 1-propanol, and isobutanol) and biodiesel itself, as a solvent, were used to improve the miscibility of the reaction mixture. Processing of neat tallow promotes an important decay of the catalytic activity due to the partial neutralization of the basic catalyst. Co-processing mixtures of tallow/SBO allowed minimizing the acidity effect. Alcohol co-solvents harmed the biodiesel yield due to competitive adsorption of alcohols with methanol on catalyst active sites but protected the catalyst against adsorption of the reaction mixture species. Biodiesel used as a solvent had an almost null effect on the esterification reaction yield, thus showing the absence of mass transfer limitation. Co-processing low-grade fat with vegetable oil seems to be a feasible strategy to process low-grade fats using basic heterogeneous catalysts, thus contributing to improving the sustainability of biodiesel production.

Calcium diglyceroxide (CaD) was used as the catalyst for biodiesel production through oil methanolysis. It was evaluated its catalytic behavior, its air expo- sure tolerance, and the Ca leaching. CaD catalyst was synthesized from food waste scallop shell derived CaO (obtained by calcination at 900 °C) by contacting with a mixture of equal volumes of glycerin and methanol at 65 °C for 2 h. The CaO obtained by calcination of scallop shell was used as reference catalyst. In standard reaction conditions (2.5 h, methanol reflux temperature, 5 wt% (oil basis) catalyst loading, and methanol:oil = 12:1 moral ratio), CaD presented lower catalytic activity than CaO (FAME yield of 92% against 99%, respectively). 24 h repined CaD presented improved catalytic behavior probably due to the formation of surface Ca −OH groups, achieving 96% of FAME yield. Thermogravimetry (TG) data showed that inorganic residue was larger for biodiesel than for glycerin, being CaD catalyst more soluble than CaO. Data showed that CaD is unstable under reaction conditions, suffering leaching, but the absence of Matter Organic Non-Glycerol (MONG) in the glycerin phase allows to neglect the homogeneous contribution of the leached catalyst. CaD formation during reaction contributes to FAME contamination with Ca and promotes catalyst deactivation thus being an undesired occurrence.

Lithium extraction from hard-rock ores has regained importance due to the increased demand for this metal to supply the growing battery market. Therefore, several studies have been focused on the lithium extraction from ores, however, leaching and purification steps are sparsely studied. Thus, the objective of this study was to evaluate the main factors affecting the water leaching step and the subsequent purification operations for lithium recovery from a lepidolite concentrate, which was processed by mechanical activation and sulphuric acid digestion. In the leaching step, among the variables studied, only one, the leaching temperature, showed a significant effect on the lithium extraction, taking into account the range of values tested. Thus, the recommended operating value for the leaching time and the L/S ratio is the minimum, while for the leaching temperature is 50°C. After optimizing the leaching operation, the purification of the leachate, by neutralization, was thoroughly performed by efficient removal of impurities (Fe, Al, Mn and Ca), allowing to obtain lithium carbonate as final product, as well as other relevant by-products, such as rubidium and potassium alums. info:eu-repo/semantics/publishedVersion

The hydrometallurgical extraction of metals from spent lithium-ion batteries (LIBs) was investigated. LIBs were first dismantled and a fraction rich in the active material was obtained by physical separation, containing 95% of the initial electrode, 2% of the initial steel and 22% of plastic materials. Several reducers were tested to improve metals dissolution in the leaching step using sulphuric acid. Sodium metabisulphite led to the best results and was studied in more detail. The best concentration of Na2S2O5 was 0.1 M. The metals dissolution increased with acid concentration, however, concentrations higher than 1.25 M are unnecessary. Best results were reached using a stirring speed of 400 min(-1). The metals leaching efficiency from the active material (Li, Mn, Ni, Co) increased with the temperature and was above 80% for temperatures higher than 60 degrees C. The dissolution of metals also rose with the increase in the liquid/solid ratio (LAS), however, extractions above 85% can be reached at LAS as lower as 4.5 L/kg, which is favourable for further purification and recovery operations. About 90% of metals extraction can be achieved after only 0.5 h of leaching. Sodium metabisulphite can be an alternative reducer to increase the leaching of Li, Mn, Co, and Ni from spent LIBs. info:eu-repo/semantics/publishedVersion

9 páginas.-- 3 figuras.-- 2 tablas.-- 83 referencias.-- Selected paper from the XVI Latin-American Congress on Chromatography (XVICOLACRO) and the 9th National Meeting on Chromatography (9ENC), 5–9 January 2016, Lisbon, Portugal., This study comprises an innovative approach based on the combination of chromatography (analytical pyrolysis and pyrolysis compound-specific isotope analysis (Py-CSIA)), light stable isotopes, microscopy and mineralogy analyses to characterize the internal layering of coralloid speleothems from the Ana Heva lava tube in Easter Island (Chile). This multidisciplinary proxy showed that the speleothems consist of banded siliceous materials of low crystallinity with different mineralogical compositions and a significant contribution of organic carbon. Opal-A constitutes the outermost grey layer of the coralloids, whereas calcite and amorphous Mg hydrate silicate are the major components of the inner whitish and honey-brown layers, respectively. The differences found in the mineralogical, elemental, molecular and isotopic composition of these distinct coloured layers are related to environmental changes during speleothem development. Stable isotopes and analytical pyrolysis suggested alterations in the water regime, pointing to wetter conditions during the formation of the Ca-rich layer and a possible increase in the amount of water dripping into the cave. The trend observed for δN values suggested an increase in the average temperature over time, which is consistent with the so-called climate warming during the Holocene. The pyrolysis compound-specific isotope analysis of each speleothem layer showed a similar trend with the bulk δC values pointing to the appropriateness of direct Py-CSIA in paleoenvironmental studies. The δC values for n-alkanes reinforced the occurrence of a drastic environmental change, indicating that the outermost Opal layer was developed under drier and more arid environmental conditions., A.Z. Miller acknowledges the support from the Marie Curie Intra-European Fellowship of the European Commission’s 7th Framework Programme (PIEF-GA-2012-328689). The Spanish Ministry of Economy and Competitiveness (MINECO, project CGL2013-41674-P) and the FEDER Funds are acknowledged for the financial support. N.T. Jiménez-Morillo thanks the MINECO for funding his pre-doctoral FPI fellowship (BES-2013-062573).