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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.
Minerals of precious metals
Published in Francis P. Gudyanga, Minerals in Africa, 2020
The process of extraction of silver from its argentite ore Ag2 S involves cyanidation leaching [475]. The crushed ore is concentrated by froth flotation and then treated with sodium cyanide solution resulting in the formation of sodium argentocyanide Na[Ag(CN)2]. Ag2S+4NaCN⇌2NaAg(CN)2+Na2S The solution of sodium argentocyanide combines with zinc dust forming sodium tetra cyanozincate and precipitated spongy silver. Zn+2NaAg(CN)2→Na2Zn(CN)4+2Ag Pure silver is obtained by fusing the spongy silver with potassium nitrate. Subsequently, the silver obtained is purified by an electrolytic process.
Structural and optical studies of silver sulfide nanoparticles from silver(I) dithiocarbamate complex: molecular structure of ethylphenyl dithiocarbamato silver(I)
Published in Journal of Sulfur Chemistry, 2020
Peter A. Ajibade, Nandipha L. Botha
Figure 2 shows the powder X-ray diffraction patterns of the silver sulfide nanoparticles synthesized at three different temperatures. The XRD pattern peaks were indexed according to the literature [32]. For AgS1 nanoparticles synthesized at 120°C, the angle 2θ = 36.75°, 40.62°, 50.37° and 53.85° are indexed to (013), (031), (014), and (−224) miller indices. The peaks 2θ = 39.90, 42.67°, 46.81°, 50.62° and 75.65°, for AgS2 nanoparticles synthesized at 180 °C corresponds to (031), (−202), (−214), (014) and (−227) miller indices respectively. AgS3 nanoparticles synthesized at 220 °C 2θ angles are 33.43°, 36.44°, 40.01°, 42.74°, 73.91°, 47.43°, 50.62°, 55.79°, 57.13° and 62.25° corresponding to (−121), (022), (031), (023), (112), (014), (−224), (−142), (042) and (015) planes respectively. The phase of the particles was determined to be acanthite α-Ag2S for AgS1 and AgS2 while AgS3 is cubic argentite β-Ag2S crystalline phase [33,34].