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Heavy Metals
Published in Abhik Gupta, Heavy Metal and Metalloid Contamination of Surface and Underground Water, 2020
Silver (Ag), a precious metal, has an atomic number of 47, an atomic weight of 107.868, and a density of 10.50 g cm–3. Many lead, zinc, and copper ores are argentiferous, that is, these contain argentite or silver sulfide (Ag2S). Silver is extracted as a by-product from the mining of these three metals. However, being a precious metal, even small amounts of silver fetch a lucrative price. Silver is also an essential constituent of calaverite, which is a gold telluride [(AuAg)Te2]. Silver, alloyed with copper to make it hard, is used for making cutlery, utensils, coins, ornaments, and jewelry. Among the other uses of silver, silver vats are used during the production of acetic acid, vinegar, and cider, because of the resistant nature of silver to acetic acid. It is also used in silver solders, dental amalgams, batteries, ceramic paints, and other items. Silver also acts as a catalyst in the synthesis of formaldehyde and acetaldehyde. The property of silver halides of reacting to light instantaneously makes them invaluable in the production of films, plates, and photographic printing paper. Silver nitrate (AgNO3) is an important laboratory reagent in analytical chemistry, and is used for making mirrors, photography, silver plating, dyeing, and numerous other uses ranging from indelible inks and water disinfectant to antiseptic ointments and astringents (Encyclopaedia of Occupational Health and Safety 2012). Silver has very strong antimicrobial properties, and nanosilver compounds are expected to revolutionize the use of silver in antimicrobial formulations.
An electrical- and chemical-free approach using microfilter and Ag-based catalysts for emergency drinking water treatment
Published in Environmental Technology, 2022
Nguyen Thi Thuy, Ngo Ngoc Tho, Nguyen Xuan Hoan, Tran Tien Khoi, Dang Van Thanh, Nguyen Trung Thanh, Ho Duc Duy, Nguyen Nhat Huy
The solution of the Ag-TiO2-SiO2 catalyst was synthesised by the sol–gel method [15,21,32]. Firstly, a solvent mixture of ethanol and isopropanol was prepared with the volume ratio of ethanol and isopropanol being 1:1. We then prepared (i) the first solution (S1) by mixing the solvent mixture with water and nitric acid, (ii) the second solution (S2) with the solvent mixture, water, and Tetraethylorthosilicate (TEOS, 98%, Merck), (iii) the third solution (S3) by the mixing of the solvent mixture and tetra-isopropyl orthotitanate (TTIP), and (iv) the final solution (S4) made of the solvent mixture, water, nitric acid and silver nitrate (AgNO3). Details of the amounts of chemicals used can be found in Supplementary data (Section 4). The S1, S2, S3, and S4 solutions were then mixed following the steps given in Supplementary data (Section 4, Figure S14). The produced sol–gel solution was hydrothermally treated using an autoclave (150 °C, 10 h) and cooled to ambient temperature. For the synthesis of the Ag catalyst solution, 0.1488 g AgNO3 (Xilong, China) was mixed with 100 mL of ethanol (Merck, Germany) at 200 rpm for 60 min. The concentration of Ag+ in this solution was equal to its concentration in the sol–gel solution above (0.945 g/L).
Extraction of nano-metals with judicious combination of microwave heating and acid leaching process from E-waste
Published in Journal of Microwave Power and Electromagnetic Energy, 2021
Satya Sai Srikant, Rajendra Prasad Mahapatra, Raghupatruni Bhima Rao
The surface plasmon absorption and hydrophobic characteristics of β- cyclodextrin (β- CD) plays an important role as complex reducing agent in order to synthesize the precious nano-particles from the mixture of aqueous chloroauric (HAuCl4) solutions and sodium hydroxide (NaOH). This solution changes from clear red solution to muddy turbid solution. After washing with de-ionized water, this aqueous solution changed from muddy turbid solution to brown colour. This colloidal aqueous solution was then stirred properly for two minutes and an aliquot of 0.025 mL of silver nitrate (AgNO3) was added and then passed through the precipitation process with butyl stearate [C22H44O2], sodium sulphite [Na2SO3]. The addition of silver nitrate formed the silver coating on the gold metal particles. After one hour, this solution was filtered out through PTFE filter having sieve size 80 nm. The collected metal nano particles (>80 nm) after filtration process followed by microwave drying shows precious nano metals like nano gold, nano silver and nano copper.
Extracellular collagenase isolated from Streptomyces antibioticus UFPEDA 3421: purification and biochemical characterization
Published in Preparative Biochemistry & Biotechnology, 2023
Elizianne Pereira Costa, Romero Marcos Pedrosa Brandão-Costa, Wendell Wagner Campos Albuquerque, Thiago Pajeú Nascimento, Amanda Emmanuelle Sales Conniff, Kethylen Barbara Barbosa Cardoso, Anna Gabrielly Duarte Neves, Juanize Matias da Silva Batista, Ana Lúcia Figueiredo Porto
Gelatin zymography was performed according to Laemmli[38] with some modifications. Separating gel (10%) was prepared containing 1 mg/mL of gelatin and 20% SDS. The purified enzyme samples were applied to the polyacrylamide gel and the electrophoresis was carried out at 4 °C. The gel was then washed in a Triton X-100 (2.5% v/v) solution for 30 min and was incubated overnight in 0.05 M Tris-HCl buffer (pH 7.8) containing 1.0 mM CaCl2 at 37 °C. The gel was stained by silver nitrate.[38]