Water Contaminants part - 5
Water contaminants
Brief information
limits of contaminants for safe drinking water and Health effects
Part-5.
17 - Silicon (Si) and water
Silicon occures abundently on earth after oxygen. Silicon found in most minerals and also in sea water and other waters as silicilic acid. silicon in sea surface water is 30 ppb, in deep water arround 2 ppm. In river water generaly 4 ppm, Silica dissolve in water slowly and form ortho silicilic acid (H4SiO4 or Si(OH)4. About 20% of dissolve silicon remove from river water because of biological or chemical trasformation process and in this way a large amount of silica transported to sea.
Free silica do not found naturally but in crystallized form under extremely high temperature. Water have very little effects on silcon solubility because of the rapidly form silicon dioxide which serve as aprotective layer.
Silicon compounds react with water for example silicon tetra fluoride with water to form hydrogen fluoride, tetra chloride react with water violently. Silicides are more reactive with first and second group than transitional metal. typical reaction include hydrogen and/or silanes (SiH4) like Na2Si + 3H2O -> Na2SiO3 + 3H2
Silicon counds are almost insoluble as compared to other minerals, see the reaction with water: SiO2(s) + 2 H2O(l) <-> H4SiO4(s)
A weak silicilic acid forms during mineral hydrolysis:
H4SiO4(s) + H2O(l) <-> H3O+(aq) + H3SiO4-(aq)
Water solubility of silicon dioxide is 0.12g/l when silicon carbide is insoluble.
Silicon as a part of various minerals may released during weathering process and may also released under water during volcanic activity. Marine sediments contain more silicon than sea surface water which actually the reason having silicon in sea water. weathering effects like in Antarcric also release silicon. Silicon naturall remove from water by plankton fixation, settling of sediments, or reaction of dissolved silicon with clay minerals (reverse weathering effects)
Sand is the main source silicon production commercially. Minerals like talc, Mica,feldspar, nepheline, olivine, vermiculite, perlite and kaolinite all contain silicon. Gemstone like opal,amethyst contain silicon.
Construction material like sand and cement contain silicon compound, calcium silicate is being used in glass and porcelain production.
Silicon used in steel, chemical and electron industries processed at high temperature. Steel and other alloys to process several products like engine block or cylinder heads.
Silicon compounds industrially used in rubber, resin and similiar compounds generally water resistant and also withstands oxidation and weathering effects. its a high temperature lubricant and generally used sealing kit for window, roof, and pipes and also in rubber hoses and plastic parts in car engines. Also used in cosmetic, for textile impregnation, in microchips as silicon is a semi conductor used in transistors and electronic parts. n-semi conductor of silicon and arsenic, p-semi conductor of silicon and boron used in solar pannels. Also used in optic lenses and prisms occures in elementry form for infrared light.
Silicon carbide as hard as diamond used as an abrasive. Natural quartz crystala or chemicllly produced have charactristic of vibrating exact frequancies when contact in electricity. It is used in watches, radios and televisions. As a cleansing agent alkaline silicones used in glue and bleaching agent for textile.
As Zeolites are silicones and applied as foam regulators in detergents as influence by water quality, some of the compounds also applied as absorents.
Health effects:
Siicon dioxide for various organism is a dietary requirement, skeleton strengthening for diatoms and sea sponges, also required for small hairs on nettles, chickens and rats need silicon for bones. For human being it is a dietary requirement for skin and connecting tissue. Silicon is essential for plants, various plants contain 200- 62,000 ppm as dry mass example are dandlion and bamboo containging silicon in stem and leaves to increase stability. Silicon is harmless in water and naturally present in large amount, Excessive amount limits algal growth, zeolite effects water organism and act like phosphate replacement in detergents.
There are three natural isotops and are non radioactive and seven instable isotopes.
Human body contain about 1g of silicon decreases with increase of age. It is a dietary requirements for human being as well other number of organism needs for bones while for human being it is for skin and connective tissues. Daily intake is 20 to 1200 mg and can get it from grains.
Silicon naturally occures as silcon, sand and other comounds but non toxic, High concentration of soluble silicon may disturb phosphorilation. Several compounds have fiber like texture and carcinogenic like asbestos. Fine particles may cause silicosis and the illness related to mine worker and stone grinders. It harden pulmonary alveoluses decreasing the flexibility resulting shortness of breath panting and coaching and all these are because of inhalation of silicon particles.
Silicon may cause auto immune disorder or even cancer in breast implant, but untill now no scientific prove for such claims. It is present in stomach tablets to treat colic and intestnal gases. Silicon compounds like silicon halogens are corrosive and toxic. Slicone tetra chloride ia an eye irritant, breathing problem and skin irritation.
Silicilic acid in drinking is relatively safe.
Purification technologies:
Silicon as silicilic acid present in drinking water need not to remove because of human health.
Silicon compounds are also used as absorbents in water purification.
18 - Silver (Ag) and water
Silver in sea water is about 2 - 100 ppt.
surface water contains even less.
River water contain about 0.3 - 1 ppb,
Phytoplankton concentration is 0.1 - 1 ppm and goes upto 104 - 105 bio concentration factor in sea water,
In oyster about 890 ppm found in tissues.
In sea water as Ag+ found as AgCl2
Silver do not react with water, air, and resistant for acid and base but can corrode with sulphure compounds.
Solubility:
Pure silver is insoluble as well as several silver compounds like silver sulphide. Silver chloride solubility 0.1 mg/l max., Silver nitrate solubilty 2450 g/l, silver fluorides is only soluble while other silver halogens are not soluble.
Silver minerals like argenite and stephanite occures in earth sulphide minerals occures while pure silver is rare and some forms as:
3 Ag2S + 2 H2O -> 6 Ag + 2 H2S + SO2
Silver is a high thermal and electrical conductivity and applied in copper, nickel and tungsten alloys. amalgam with high mercury content. Silver is applied in electronics, its application in jewellery, coins, and also in cutlery, also used in silver layering including mirrors.
Silver compounds applied in photo and films developing chemicals, used as catalyser in many chemical processes also used in battery production.
Applied as colouring agent in food stuffs, act as preservatives and disinfectant. AgI used in atmosphere to prevent hailing, it is a by-product in metal industries.
110 m of its isotop is used in nuclear physics.
Environmental effects:
Silver is not a dietary requirement even lethal to bacteria and can cause fungi reproduction because of Ag+ ions.Oral uptake by warm blooded organism only 10% absorbed. mammals uptake by plants have about 4 - 24 ppb of silver.
Without any biological purpose plant absorb silver about 0.03 - 0.5 ppm but fungi and green algae may get about 200 ppm.
Big amount of silver not found in soil but in minning areas 44 ppm silver found, anyway in normally dried soil the concentration may exceed to 100 ppb.
Normally silver in soil or surface water do not cause any environmental problem.
Toxity of LD50 value for silver compounds, like silver oxide for rates is 2820 mg/kg, silver nitrate the LD50 for mice oral intake is 50mg/kg. For Dogs 2.3g of silver nitrate is lethal. Silver difluoride is extreamly toxic and is water soluble. silver has a broad spectrum toxicity.
Its not a carcinogenic but can implant under animal skin of animals and can cause cancer.
It has 2 stable and 24 instable isotopes (radioactive)
Health effects of silver in water.
Its not a dietary requirement of human beings, adults contain about 2mg, our daily intake is about 20 - 80 μg, in which only 10% absorb, large amount may be toxic because of silver ions affinity for sulphur hydryl and amino acid group having complexation with amino acids, nucleic acids and other compounds in the body.Toxicity relatively less on oral uptake because low absorption in the body for silver.
Silver generally deposited in connective tissue, skin and eyes turning black to grey colouring. In about 50 years accumulate about 9 mg of silver.
Guideline for drinking water.
Guide line for drinking water is 0.05 mg/l, Silver may bind with sulphur in food in boiling water, Silver is harm full for oral intake, it irritates eyes, respiratory tract and skin. Silver nitrate being a strong oxidant is more harmful causing corrosion and oral uptake may cause vomiting, dizziness and diarrhoea. The silver salt uptake may protect itself converting to insoluble silver chloride.
Silver salt like silver nitrate is being used fo disinfection in drinking water.
Purification:
Ion exchange method can be used for removing silver, the other silver and its compounds can be removed by precipitation after coagulation. Active carbon and sand filteration can be the efficient methods.
For purification used in swimming pool for water disinfection, small amount is not health hazard
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This is the end of Part five. Come back later for the next Part.
References: taken from Lenntech
Brief information
limits of contaminants for safe drinking water and Health effects
Part-5.
17 - Silicon (Si) and water
Silicon occures abundently on earth after oxygen. Silicon found in most minerals and also in sea water and other waters as silicilic acid. silicon in sea surface water is 30 ppb, in deep water arround 2 ppm. In river water generaly 4 ppm, Silica dissolve in water slowly and form ortho silicilic acid (H4SiO4 or Si(OH)4. About 20% of dissolve silicon remove from river water because of biological or chemical trasformation process and in this way a large amount of silica transported to sea.
Free silica do not found naturally but in crystallized form under extremely high temperature. Water have very little effects on silcon solubility because of the rapidly form silicon dioxide which serve as aprotective layer.
Silicon compounds react with water for example silicon tetra fluoride with water to form hydrogen fluoride, tetra chloride react with water violently. Silicides are more reactive with first and second group than transitional metal. typical reaction include hydrogen and/or silanes (SiH4) like Na2Si + 3H2O -> Na2SiO3 + 3H2
Silicon counds are almost insoluble as compared to other minerals, see the reaction with water: SiO2(s) + 2 H2O(l) <-> H4SiO4(s)
A weak silicilic acid forms during mineral hydrolysis:
H4SiO4(s) + H2O(l) <-> H3O+(aq) + H3SiO4-(aq)
Water solubility of silicon dioxide is 0.12g/l when silicon carbide is insoluble.
Silicon as a part of various minerals may released during weathering process and may also released under water during volcanic activity. Marine sediments contain more silicon than sea surface water which actually the reason having silicon in sea water. weathering effects like in Antarcric also release silicon. Silicon naturall remove from water by plankton fixation, settling of sediments, or reaction of dissolved silicon with clay minerals (reverse weathering effects)
Sand is the main source silicon production commercially. Minerals like talc, Mica,feldspar, nepheline, olivine, vermiculite, perlite and kaolinite all contain silicon. Gemstone like opal,amethyst contain silicon.
Construction material like sand and cement contain silicon compound, calcium silicate is being used in glass and porcelain production.
Silicon used in steel, chemical and electron industries processed at high temperature. Steel and other alloys to process several products like engine block or cylinder heads.
Silicon compounds industrially used in rubber, resin and similiar compounds generally water resistant and also withstands oxidation and weathering effects. its a high temperature lubricant and generally used sealing kit for window, roof, and pipes and also in rubber hoses and plastic parts in car engines. Also used in cosmetic, for textile impregnation, in microchips as silicon is a semi conductor used in transistors and electronic parts. n-semi conductor of silicon and arsenic, p-semi conductor of silicon and boron used in solar pannels. Also used in optic lenses and prisms occures in elementry form for infrared light.
Silicon carbide as hard as diamond used as an abrasive. Natural quartz crystala or chemicllly produced have charactristic of vibrating exact frequancies when contact in electricity. It is used in watches, radios and televisions. As a cleansing agent alkaline silicones used in glue and bleaching agent for textile.
As Zeolites are silicones and applied as foam regulators in detergents as influence by water quality, some of the compounds also applied as absorents.
Health effects:
Siicon dioxide for various organism is a dietary requirement, skeleton strengthening for diatoms and sea sponges, also required for small hairs on nettles, chickens and rats need silicon for bones. For human being it is a dietary requirement for skin and connecting tissue. Silicon is essential for plants, various plants contain 200- 62,000 ppm as dry mass example are dandlion and bamboo containging silicon in stem and leaves to increase stability. Silicon is harmless in water and naturally present in large amount, Excessive amount limits algal growth, zeolite effects water organism and act like phosphate replacement in detergents.
There are three natural isotops and are non radioactive and seven instable isotopes.
Human body contain about 1g of silicon decreases with increase of age. It is a dietary requirements for human being as well other number of organism needs for bones while for human being it is for skin and connective tissues. Daily intake is 20 to 1200 mg and can get it from grains.
Silicon naturally occures as silcon, sand and other comounds but non toxic, High concentration of soluble silicon may disturb phosphorilation. Several compounds have fiber like texture and carcinogenic like asbestos. Fine particles may cause silicosis and the illness related to mine worker and stone grinders. It harden pulmonary alveoluses decreasing the flexibility resulting shortness of breath panting and coaching and all these are because of inhalation of silicon particles.
Silicon may cause auto immune disorder or even cancer in breast implant, but untill now no scientific prove for such claims. It is present in stomach tablets to treat colic and intestnal gases. Silicon compounds like silicon halogens are corrosive and toxic. Slicone tetra chloride ia an eye irritant, breathing problem and skin irritation.
Silicilic acid in drinking is relatively safe.
Purification technologies:
Silicon as silicilic acid present in drinking water need not to remove because of human health.
Silicon compounds are also used as absorbents in water purification.
18 - Silver (Ag) and water
Silver in sea water is about 2 - 100 ppt.
surface water contains even less.
River water contain about 0.3 - 1 ppb,
Phytoplankton concentration is 0.1 - 1 ppm and goes upto 104 - 105 bio concentration factor in sea water,
In oyster about 890 ppm found in tissues.
In sea water as Ag+ found as AgCl2
Silver do not react with water, air, and resistant for acid and base but can corrode with sulphure compounds.
Solubility:
Pure silver is insoluble as well as several silver compounds like silver sulphide. Silver chloride solubility 0.1 mg/l max., Silver nitrate solubilty 2450 g/l, silver fluorides is only soluble while other silver halogens are not soluble.
Silver minerals like argenite and stephanite occures in earth sulphide minerals occures while pure silver is rare and some forms as:
3 Ag2S + 2 H2O -> 6 Ag + 2 H2S + SO2
Silver is a high thermal and electrical conductivity and applied in copper, nickel and tungsten alloys. amalgam with high mercury content. Silver is applied in electronics, its application in jewellery, coins, and also in cutlery, also used in silver layering including mirrors.
Silver compounds applied in photo and films developing chemicals, used as catalyser in many chemical processes also used in battery production.
Applied as colouring agent in food stuffs, act as preservatives and disinfectant. AgI used in atmosphere to prevent hailing, it is a by-product in metal industries.
110 m of its isotop is used in nuclear physics.
Environmental effects:
Silver is not a dietary requirement even lethal to bacteria and can cause fungi reproduction because of Ag+ ions.Oral uptake by warm blooded organism only 10% absorbed. mammals uptake by plants have about 4 - 24 ppb of silver.
Without any biological purpose plant absorb silver about 0.03 - 0.5 ppm but fungi and green algae may get about 200 ppm.
Big amount of silver not found in soil but in minning areas 44 ppm silver found, anyway in normally dried soil the concentration may exceed to 100 ppb.
Normally silver in soil or surface water do not cause any environmental problem.
Toxity of LD50 value for silver compounds, like silver oxide for rates is 2820 mg/kg, silver nitrate the LD50 for mice oral intake is 50mg/kg. For Dogs 2.3g of silver nitrate is lethal. Silver difluoride is extreamly toxic and is water soluble. silver has a broad spectrum toxicity.
Its not a carcinogenic but can implant under animal skin of animals and can cause cancer.
It has 2 stable and 24 instable isotopes (radioactive)
Health effects of silver in water.
Its not a dietary requirement of human beings, adults contain about 2mg, our daily intake is about 20 - 80 μg, in which only 10% absorb, large amount may be toxic because of silver ions affinity for sulphur hydryl and amino acid group having complexation with amino acids, nucleic acids and other compounds in the body.Toxicity relatively less on oral uptake because low absorption in the body for silver.
Silver generally deposited in connective tissue, skin and eyes turning black to grey colouring. In about 50 years accumulate about 9 mg of silver.
Guideline for drinking water.
Guide line for drinking water is 0.05 mg/l, Silver may bind with sulphur in food in boiling water, Silver is harm full for oral intake, it irritates eyes, respiratory tract and skin. Silver nitrate being a strong oxidant is more harmful causing corrosion and oral uptake may cause vomiting, dizziness and diarrhoea. The silver salt uptake may protect itself converting to insoluble silver chloride.
Silver salt like silver nitrate is being used fo disinfection in drinking water.
Purification:
Ion exchange method can be used for removing silver, the other silver and its compounds can be removed by precipitation after coagulation. Active carbon and sand filteration can be the efficient methods.
For purification used in swimming pool for water disinfection, small amount is not health hazard
---------------------------------------------------------------------------------
This is the end of Part five. Come back later for the next Part.
References: taken from Lenntech
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