Project description:Recently, tungsten has drawn worldwide attention considering its high supply risk and economic importance in the modern society. Skarns represent one of the most important types of tungsten deposits in terms of reserves. They contain fine-grained scheelite (CaWO4) associated with complex gangue minerals, i.e., minerals that display similar properties, particularly surface properties, compared to scheelite. Consistently, the froth flotation of scheelite still remains, in the twenty first century, a strong scientific, industrial, and technical challenge. Various reagents suitable for scheelite flotation (collectors and depressants, mostly) are reviewed in the present work, with a strong focus on the separation of scheelite from calcium salts, namely, fluorite, apatite, and calcite, which generally represent significant amounts in tungsten skarns. Albeit some reagents allow increasing significantly the selectivity regarding a mineral, most reagents fail in providing a good global selectivity in favor of scheelite. Overall, the greenest, most efficient, and cheapest method for scheelite flotation is to use fatty acids as collectors with sodium silicate as depressant, although this solution suffers from a crucial lack of selectivity regarding the above-mentioned calcium salts. Therefore, the use of reagent combinations, commonly displaying synergistic effects, is highly recommended to achieve a selective flotation of scheelite from the calcium salts as well as from calcium silicates.
Project description:In the present work experiments for single mineral flotation against LiAlO2 and melilite s.s. were carried out for seven ionic liquids (ILs). From these, IL-1 with an imidazolium cation and a bromide anion and IL-7 with a pyridinium cation and a bromide anion were selected for further flotation experiments (dosage, pH). Flotation experiments were also conducted using naphthenic acid, a conventional flotation fatty acid-based collector, and FS-2, a commercial collector in order to compare the results with ILs. Moreover, the effects of different anions in the ILs on the flotation were evaluated and a significant influence on the hardness of anions was found on the flotation process. Finally, a pre-functionalization was also explored with modified cholesterol derivatives, comparing the effect of cholesterylsulfate and cholesterylphosphate on the flotation of LiAlO2 and melilite s.s. This study is vital for the further optimization of lithium recovery from the pyrometallurgical recycling path of lithium-ion batteries and the flotation of primary minerals such as aluminosilicates.
Project description:In this work froth flotation studies with LiAlO2 (lithium-containing phase) and Melilite solid solution (gangue phase) are presented. The system was optimized with standard collectors and with compounds so far not applied as collectors. Furthermore, the principle of self-assembled monolayers was introduced to a froth flotation process for the first time resulting in excellent yields and selectivities.
Project description:Fluorine (F) enrichment originating from natural sources is difficult to remove using chemical washing methods due to the large chemical-resistant residual fraction. This study evaluates the feasibility of using a froth-flotation separation method to remediate soil with a high F concentration caused by mica weathering, and it investigates the optimal conditions for this process, including pH of the slurry, collector dosage, and sample mechanical preparation strategy. The established optimum conditions are pH 3.5, 300 mg/kg collector dosage (tallow amine acetate), which can effectively separate quartz and mica, and a sieving-and-milling strategy that involves discarding particles of size < 0.05 mm, milling those in the range of 0.5-2.0 mm (until < approx. 0.3 mm), and mixing particles with sizes in the range of 0.05-0.5 mm. The target contamination level of 400 mg/kg for the test soil was not met after the first flotation separation process. However, after milling the residue of the first process and subjecting it to a second flotation separation process, the required contamination level was achieved. Consequently, the proposed froth-flotation separation process can be used as a successful alternative technique to remediate F-enriched soils from natural origin that have highly chemical-resistant forms.
Project description:To evaluate the biological impact of cellulose nanocrystals (CNCs) at the transcriptional level, we conducted whole-genome microarray analyses on rat alveolar macrophages (NR8383) exposed to CNCs with different physicochemical properties.
Project description:The majority of reagents currently used in mineral flotation processes are fossil-based and potentially harmful to the environment. Therefore, it is necessary to find environmentally-friendly alternatives to reduce the impact of mineral processing activities. Chitin nanocrystals are a renewable resource that, due to the natural presence of amino groups on its surface, represents a promising collector for various minerals of economic relevance. This study examines the one-pot functionalization of chitin nanocrystals with aldehyde structures to obtain hydrophobized colloids suitable for mineral flotation. The chemical properties of these nano-colloids were investigated by nuclear magnetic resonance spectroscopy, their colloidal behavior and structure by electrophoretic light scattering and atomic force microscopy, and their wettability through water contact angle measurements. The functionalized N-alkylated chitin nanocrystals possessed a hydrophobic character, were able to dress mineral particles and featured a performance in the flotation of malachite similar to commercial collectors, which proves the high potential of chitin nanocrystals in this field of application.
Project description:Due to their exceptional properties, cellulose nanocrystals (CNCs) have been proposed for various applications in sustainable materials science. However, state-of-the-art production methods suffer from low yields and rely on hazardous and environmentally harmful chemicals, representing a bottleneck for more widespread utilization of CNCs. In this study, we present a novel two-step approach that combines previously established HCl gas hydrolysis with electrochemical TEMPO oxidation. This unique method allows the collection of easily dispersible CNCs with high carboxylate contents in excellent overall yields of 71%. The electromediated oxidation was conducted in aqueous conditions without the usually required cocatalysts, simplifying the purification of the materials. Moreover, the proposed process is designed for facile recycling of the used reagents in both steps. To evaluate the sustainability and scalability, the environmental impact factor was calculated, and a cost analysis was conducted.
Project description:Widespread concerns over the impact of human activity on the environment have resulted in a desire to replace artificial functional materials with naturally derived alternatives. As such, polysaccharides are drawing increasing attention due to offering a renewable, biodegradable, and biocompatible feedstock for functional nanomaterials. In particular, nanocrystals of cellulose and chitin have emerged as versatile and sustainable building blocks for diverse applications, ranging from mechanical reinforcement to structural coloration. Much of this interest arises from the tendency of these colloidally stable nanoparticles to self-organize in water into a lyotropic cholesteric liquid crystal, which can be readily manipulated in terms of its periodicity, structure, and geometry. Importantly, this helicoidal ordering can be retained into the solid-state, offering an accessible route to complex nanostructured films, coatings, and particles. In this review, the process of forming iridescent, structurally colored films from suspensions of cellulose nanocrystals (CNCs) is summarized and the mechanisms underlying the chemical and physical phenomena at each stage in the process explored. Analogy is then drawn with chitin nanocrystals (ChNCs), allowing for key differences to be critically assessed and strategies toward structural coloration to be presented. Importantly, the progress toward translating this technology from academia to industry is summarized, with unresolved scientific and technical questions put forward as challenges to the community.
Project description:Mosquitoes are the deadliest of all combined insects and animals affecting millions and killing hundreds or thousands of people each year. Existing protection methods however are limited and include volatile compounds that actively repel mosquitoes such as N,N-Diethyl-meta-toluamide (DEET) or different essential oils such as geraniol and citronella. Most are odorous compounds and require organic solvents for dispersion. This work investigates the barrier properties of cellulose nanocrystals (CNCs). CNCs are known to self-assemble in strong, transparent, chemical barrier films. They are fully bio-based, and their surface chemistry is ideal for aqueous dispersion of many compounds. This work saw a significant 80% decrease in feeding on human skin when a thin CNC coat was applied. The effect was further confirmed by artificial feeding on Aedes aegypti wherein CNC appears to act as a chemical camouflage to the many cues sought by the insects. The combined effect of CNC with indole reduced egg laying post exposure to mammalian blood close to null with 99.4% less eggs as compared to control. The chemical barrier effect was assessed through a simple headspace experiment showing that the same CNC coat blocked the passage of ammonium hydroxide vapor, a commonly used mosquito attractant, when applied on a filter paper membrane.