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Silver (Ag) và water Silver & water: reaction mechanisms, environmental impact & health effects Seawater contains approximately 2-100 ppt of silver, và the surface concentration may be even lower. River water generally contains approximately 0.3-1 ppb of silver. The phytoplankton concentration is 0.1-1 ppm (dry mass), leading lớn a 104-105 bio concentration factor in seawater. In oyster tissue concentrations of approximately 890 ppm (dry mass) were found. Dissolved in water silver mainly occurs as Ag+ (aq), & in seawater as AgCl2- (aq). In what way and in what khung does silver react with water? Silver does not react with pure water. Is is stable in both water and air. Moreover, it is acid & base resistant, but it corrodes when it comes in tương tác with sulphur compounds. Solubility of silver và silver compounds Under normal conditions silver is water insoluble. This also applies to lớn a number of silver compounds, such as silver sulphide. Some other sulphur compounds are more or less water soluble. For example, silver chloride has a water solubility of 0.1 mg/L, maximum. Silver nitrate has a water solubility of 2450 g/L. Silver fluorides are generally water soluble, but other silver halogens are not. Why is silver present in water? Silver mainly occurs in argenite & stephanite, from which it is released through weathering. In soils it is mainly present in sulphide minerals. Naturally occurring pure silver is extremely rare và is probably formes through the following reaction mechanism: 3 Ag2S + 2 H2O -> 6 Ag + 2 H2S + SO2 Besides gold, silver is the most bendable of all metals. It is known for its high thermal và electrical conductivity, its reflective power and its white colour. It is applied for example in copper, nickel và tungsten alloys. Amalgam is a silver alloy with a high mercury content. In electronics, silver is applied for outlets. Commonly known are applications in jewellery, coins and cutlery. Objects are often provided with a silver layer, including mirrors. Silver compounds play an important role in photo and film production, và are applied in developing chemicals. It serves as a catalyser in many chemical processes. Silver oxides are applied in battery production. Colouring agents for food stuffs, preservatives và disinfectants may contain silver. Silver is added to the atmosphere as AgI lớn prevent hail. It is generally a by-product of metal refinery, and may be recycled. The 110mAg isotope is applied in nuclear physics. What are the environmental effects of silver in water? Silver is not a dietary requirement for organisms. It may even be lethal lớn bacteria, and it inhibits fungi reproduction. This is mainly caused by Ag+ ions. At oral silver uptake by warm-blooded organisms, about 10% is absorbed. Mammal flesh contains approximately 4-24 ppb (dry mass) of silver. Mammals take up silver mainly through plant feed. Plants may absorb silver, although it has no biological use. Values of between 0.03 và 0.5 ppm (dry mass) were measured in the past. Fungi and green algae may even obtain a silver content of 200 ppm (dry mass). Soils vì chưng not contain great amounts of silver. However, areas rich in minerals may contain higher amounts. In mining areas soil silver amounts of up to lớn 44 ppm were found. In normal air-dried soil concentrations vì not exceed 100 ppb. In water silver và silver compounds are toxic khổng lồ micro organisms. Fish contain approximately 11 ppm of silver. Silver toxicity lớn fish is reduced by water. Depending on water hardness, the lethal concentration for freshwater fish lies between 4 & 280 ppm. Freshwater plants tolerate between 30 & 7,500 ppb silver, depending on the species. The lethal concentration for daphnia is approximately 0.25 ppb, và for amphipods at 4,500 ppb. Naturally occurring silver concentrations in soil & surface water bởi vì not normally cause any environmental problems. LD50 values were determined for various silver compounds. For silver oxide the LD50 for rats at oral intake is 2820 mg/kg, & for silver nitrate the LD50 for mice at oral intake is 50 mg/kg. For dogs 2.3 g of silver nitrate is lethal. Silver difluoride is extremely toxic, & it is also excellently water soluble. Silver toxicity has a very broad spectrum. Silver is not known to lớn be carcinogenic. However, when it is directly implanted under the skin of animals it can cause cancer. Silver has two stable & twenty four instable (radioactive) isotopes. What are the health effects of silver in water? Silver is not a dietary requirement for humans. The body of an adult contains approximately 2 mg of silver. Our daily intake of silver is 20-80 μg, of which approximately 10% is absorbed. These amounts are not health threatening. In larger amounts, some silver compounds may be toxic, because silver ions have a high affinity for sulphur hydryl và amino groups, và therefore complexation with amino acids, nucleic acids and other compounds occurs in the body. We known the mechanism of toxicity, so we also known a number of detoxification methods. The toxic mechanism is relatively small at oral uptake, because of the low absorption capacity of the toàn thân for silver. Silver that ends up in the body toàn thân is generally deposited in connective tissue, skin và eyes và causes a gray to đen colouring. Within 50 years, one is able to accumulate approximately 9 mg of silver. The drinking water guideline for silver is 0.05 mg/L, if a guideline is fixed at all. This is mainly because silver may bind to sulphur in food in boiling water. Silver oxide is harmful upon swallowing, because it irritates the eyes, respiratory tract and skin. Silver nitrate is much more harmful, because it is a strong oxidant. It causes corrosion and at oral uptake it leads khổng lồ vomiting, dizziness and diarrhoea. At silver salt uptake the body toàn thân may protect itself by converting them to lớn insoluble silver chlorides. Silver is a bactericide, và may therefore be applied in water disinfection. Which water purification technologies can be applied lớn remove silver from water? Ionic silver may be removed from water by ion exchange. Some silver compounds may precipitate by coagulation. Two other efficient methods include active carbon filtration và sand filtration. Silver is applied in water purification for swimming pool water disinfection. Only small amounts are applied that are not a health hazard. Literature and the other elements và their interaction with water