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Industrial minerals
Published in Francis P. Gudyanga, Minerals in Africa, 2020
Commercially, elemental selenium is produced from selenide anode mud as a by-product in the electrolytic refining of sulphide ores such as copper, nickel and lead. The industrial production of selenium is via the extraction of selenium dioxide from the residues during the purification of copper. The residue is oxidised by sodium carbonate to produce the selenium dioxide which is then mixed with water and the solution is acidified to form selenous acid in the oxidation step. Selenous acid is reduced to elemental selenium [624,625] by bubbling it with sulphur dioxide. The power necessary to operate the electrolysis cells is significantly decreased during the electrowinning of manganese by addition of selenium dioxide [626]. The current production of copper is a combination of solvent extraction and electrowinning (SXEW) altering the availability of selenium as only a comparably small part of the selenium in the ore is con-leached with copper [623].
Metals in the workplace
Published in Sue Reed, Dino Pisaniello, Geza Benke, Kerrie Burton, Principles of Occupational Health & Hygiene, 2020
The acute toxicities of inorganic selenium compounds vary greatly. Hydrogen selenide, selenium oxychloride, selenium dioxide and selenium hexafluoride are highly poisonous, while the element and sulfides are much less toxic. Selenium dust, selenium dioxide and hydrogen selenide are more likely to be encountered in the workplace. The chronic effects of nearly all forms of selenium in humans appear to be similar: depression, languor, nervousness, dermatitis, upset stomach, giddiness, a garlic odour of breath and sweat, excessive dental caries, and in extreme cases loss of fingernails and hair. Most knowledge of selenium’s toxic effects is derived from clinical toxicology and the incidence of selenium poisoning as a result of ingestion of seleniferous grains and other food; there have been no reports of disabling chronic disease or death from industrial exposures. The SWA (2012) WES-TWA standard is 0.1 mg/m3 for selenium compounds (excluding hydrogen selenide), which is half that of the ACGIH® (2013) 0.2 mg/m3, to minimise irritation of the eye and upper respiratory tract as well as systemic effects such as headache, garlic breath, skin rashes, and the like. The WES-TWA standard for hydrogen selenide is 0.05 ppm or 0.16 mg/m3.
Metals in the workplace
Published in Sue Reed, Dino Pisaniello, Geza Benke, Principles of Occupational Health & Hygiene, 2020
The acute toxicities of inorganic selenium compounds vary greatly. Hydrogen selenide, selenium oxychloride, selenium dioxide and selenium hexafluoride are highly poisonous, while the element and sulfides are much less toxic. Selenium dust, selenium dioxide and hydrogen selenide are more likely to be encountered in the workplace. The chronic effects of nearly all forms of selenium in humans appear to be similar: depression, languor, nervousness, dermatitis, upset stomach, giddiness, a garlic odour of breath and sweat, excessive dental caries, and in extreme cases loss of fingernails and hair. Most knowledge of selenium’s toxic effects is derived from clinical toxicology and the incidence of selenium poisoning as a result of ingestion of seleniferous grains and other food; there have been no reports of disabling chronic disease or death from industrial exposures. The Safe Work Australia (2018b) WES-TWA standard is 0.1 mg/m3 for selenium compounds (excluding hydrogen selenide), which is half that of the ACGIH® (2019) and OSHA (2017) 0.2 mg/m3 limit, set to minimise irritation of the eyes and upper respiratory tract as well as systemic effects such as headache, garlic breath, skin rashes and the like. The OEL-TWA standard for hydrogen selenide is typically 0.05 ppm or 0.16 mg/m3.
Kinetic mechanism of selenium leaching from selenium-rich acid sludge in NaOH solution
Published in Canadian Metallurgical Quarterly, 2023
Xijian Pan, Yan Hong, Tu Hu, Libo Zhang, Kun Yang
At present, domestic and foreign methods of selenium extraction mainly include pyrometallurgy and hydrometallurgy. The mainstream thermal method includes oxidation roasting and sulfuric acid roasting, through which selenium is converted into selenium dioxide and reduced to monolithic selenium by passing sulfur dioxide or sodium sulfite into the aqueous solution. However, the selenium obtained by this process has low purity, low recovery, high slag production, relatively high energy consumption, and the fumes produced during the roasting process tend to corrode the equipment and pollute the environment [12–14]. Wet recovery of selenium mainly consists of acid leaching and alkaline leaching. Although some wet metallurgical methods can extract selenium effectively, the whole process becomes complicated because solvent extraction, ion exchange is needed to separate other elements [15–18]. To avoid this problem, selenium can be leached by sodium hydroxide, which is easy to operate, simple to set up and pollution-free. Liu [19] et al. studied the leaching of selenium from anode sludge with sodium hydroxide and oxygen under pressure, and the leaching rate of selenium can reach 99%. Yasin [20] et al. suggested that sodium hydroxide can leach elemental selenium effectively. Peng [21] et al. studied the leaching of selenium by sodium hydroxide using hydrogen peroxide as oxidant. The leaching of selenium from selenium-containing materials by sodium hydroxide has been extensively conducted, so it is important to study the leaching kinetics of selenium by sodium hydroxide.
Comparison of the effectiveness of textiles containing metal nanoparticle and metal-organic frameworks for protection against ultraviolet radiation: a systematic review and meta-analysis
Published in The Journal of The Textile Institute, 2022
Hadiseh Rabiei, Majid Montazer, Somayeh Farhang Dehghan, Shokooh Sadat Khaloo, Saeed Yousefinejad, Soheil Hassanipour, Amir Sharifi
Diverse properties can be added to the textiles using various nanomaterials and NPs; like increased UVR protection (Kalantary et al., 2020). NPs are more effective against UVR absorption and emission compared to bulk particles. Nanofibers have a very large surface area, and also the reduced distance between them help to increase UVR protection. Titanium dioxide (TiO2), zinc oxide (ZnO), selenium dioxide (SeO2), aluminum dioxide (AlO2), and carbon nanotubes are different kinds of NPs for these purposes. Amongst them, TiO2 is considered to be one of the best choices due to its low price, low toxicity, vast effective area, high surface energy, and being easy to synthesis (Paul et al., 2010). Studies have shown that the absorption of UVR is the protection mechanism of titanium in any size (Yang et al., 2004).
Multifunctional 1,10-phenanthroline derivative and its metal complexes as an anti-Alzheimer’s agent: structure-based drug design, synthesis, characterization and pharmacological studies
Published in Journal of Coordination Chemistry, 2020
E. H. Edinsha Gladis, K. Nagashri, A. Suman, J. Joseph
Preparation of the desired 1,10-phenanthroline derivative started with 2,9-dimethyl-1,10-phenanthroline in two steps. The first synthetic step involved the reaction of 2,9-dimethyl-1,10-phenanthroline with selenium dioxide in dioxane at room temperature with stirring for 5 h to obtain the desired 1,10-phenanthroline-2,9-dicarbaldehyde. It was then condensed with 3-aminonaphthalen-2-ol in hot ethanolic solution for 3 h and refluxed to obtain the ligand (H2L). Metal acetate(s) were reacted to achieve the desired complexes for medicinal applications. Elemental composition, molecular mass and conductivity values suggested molecular formulas of metal chelate with excellent matching with theoretical results. With the assistance of spectral measurements, thermal and magnetic behavior, structural elucidation was attempted and supported the proposed structural formulas. In water or in non-polar organic solvents, the complexes were insoluble, but partly soluble in DMSO or DMF. Numerous attempts, such as crystallization using solvent mixtures and low temperatures, failed for the growth of single crystals appropriate for X-ray crystallography. The analytical, spectroscopic and magnetic data, however, permitted assigning possible structures of the synthesized complexes.