A systematic review of sustainable gold extraction from raw ores using alternative leaching reagents

ABSTRACT: Drawing on recent experimental and commercial developments, this review reappraises potential substitute leach reagents for cyanide in the gold mining sector. In addition to extraction, the application of these reagents in the gold processing, pre-treatment and gold purification stages is explored. The main objective here is to discuss how the gold extraction process can be more sustainable, with a view to developing more greener leaching reagents.info:eu-repo/semantics/publishedVersio

Portuguese ornamental stones

Portugal produces a great diversity of ornamental stones. Besides the internationally known white and pink marbles, also light cream limestones are produced, as well as grey, yellow and pink granites, and dark grey slates. From these, limestones are the most request variety today, especially by the Chinese market

Evaluation of the portuguese ornamental stone resources

Portugal produces a great diversity of ornamental stones. Besides the internationally known white and pink marbles, also light cream limestones are produced, as well as grey, yellow and pink granites, and dark grey slates.  A first exercise is presented on the evaluation of the available resources of ornamental stones in the whole Portuguese territory. The results show a total availability of 410 million cubic meters, of which 274 million refer to granite, 76 million to limestone, 51 million to marble, and 9 million to slate

Rede de laboratórios para a energia e geologia

RESUMO: O Laboratório Nacional de Energia e Geologia (LNEG), nas suas áreas de competências reuniu as competências de anteriores instituições com um histórico de trabalho em Laboratórios com acreditação desde os anos 80. No LNEG, estes Laboratórios focaram-se em atividades da área de energia e geologia, mantendo as suas acreditações mas sentiram a necessidade de trabalhar em rede.info:eu-repo/semantics/publishedVersio

Separation of lepidolite from hard-rock pegmatite ore via dry processing and flotation

ABSTRACT: A mineralogical study of Goncalo lithium-bearing mica-rich pegmatite ore (Portugal) indicated that lepidolite occurs in coarse-grained textures, which allows an appreciable liberation of gangue minerals (quartz, k-feldspar, and albite) from lepidolite. However, the intergrowth of these gangue minerals results in uncomplicated liberation (i.e., inclusions). Taking advantage of this coarse gangue liberation, optical ore sorting through image analysis was attempted in order to predict the grades of different-sized fractions using a random comminution algorithm. The ore-sorting process allowed the production of a marketable Li pre-concentrate product for metallurgy. Moreover, this method also highlighted the possible valuation of the reject as low-Li-content quartz-feldspar mixtures for the ceramic industry (reduction in the temperature of porosity closing). Furthermore, a scaled approach of grinding and sieving allowed the formation of a lepidolite-rich fraction (>210 mu m), which was processed using an electrostatic separator by varying key process parameters. The lepidolite and muscovite were separated to obtain a Li pre-concentrate assaying 3.5 % Li2O from a feed grade containing 1.8 % Li2O. Nevertheless, according to the zeta-potential measurements, the flotation test performed with the finer-sized fraction (-210 + 63 mu m) showed that lepidolite flotation was optimised between pH 3 and 5. In this pH range, concentrates from the rougher stage assayed 4.2-4.5 % Li2O, corresponding to 87-95 % Li recovery. At pH > 5, the selectivity decreases, and SiO2 analysis suggests the flotation of quartz and other silicates rather than lepidolite. Feldspar/quartz flotation was also tested using lepidolite flotation rejects to promote the separation of feldspars from quartz and obtain products for ceramic applications.info:eu-repo/semantics/publishedVersio

Survey on the Advancements of Dielectric Fluids and Experiment Studies for Distribution Power Transformers

-The main objective of this work is to summarize the most commonly used dielectric fluids in the power distribution transformers, as well as to discuss what are the latest and the rationale behind those trends. The favorable and unfavorable reasons for any choice behind each of those dielectric fluids will be discussed. Additionally, this work also advances the power distribution transformers health index most commonly used to assess the condition of the transformer. (c) 2021, European Association for the Development of Renewable Energy, Environment and Power Quality (EA4EPQ). All rights reserved