Water Contaminants - Part 3
Water contaminants
Part 3
Brief information
limits of contaiminants for safe drinking water
and Health effects
Lithium in water (Li + H2O)
Lithium in
Seawater arround 0.17 ppm
Rivers only 3 ppb
Mineral water 0.05-1 mg/l
Large amounts found in water from Karlsbad, Marienbad and Vichy and found as Li+ (aq).
Lithium when react with water forms lithium hydroxide and hydrogen, it is an exothermic reaction and temperature reaches upto 750oC releasing hydrgen gas and it can be used as hydrogen storage. Soluability of lithium in water is 2800 liter/kg
2 Li(s) + 2 H2O -> 2 LiOH (aq) + H2(g)
Solubility of other lithium compounds like lithium chloride, lithium carbonate, lithium phosphate, lithium fluoride and lithium hydroxide are less water soluble for example Lithium hydroxide has a 129 g/L solubility further more elementry lithium has less soluability in water.
Lithium occure as minerals like amblygonite, petalite, lepidolite and spodumene.
Being a lightest element it is used in Aluminium, Magnesium and lead aloy to make it lighter and more stable. Maximum use in batteries.
Lithium carbonate used to glaze in glass industry and used in oils and fats to increase viscosity.
Lithium chloride is a solid having an enormous water holding capacity. It is applied in air-conditioning, and dry industrial gases and also applied as antifreeze. Also used as catalyser and some compounds also used in rocket fuel.
As a lubricant at high and low temperature some compounds used. it is a successfull used in medicine for bipolar syndrome treatment. Also used as air cleansing gas to bind carbon dioxide. Lithium as tritium (3H) used in nuclear weaponse.
Lithium is water hazard class 1 and weakly harmfull, in mainland absirbed by plants but not as dietary mineral but just stimulating plants growth. excess may be toxic but calcium may be used to reduce toxicity in soil. lithium in plants may be 0.2 to 30ppm.
Lithium exists as two stable and three instable isotopes.
Human body contain about 7 mg of lithium and not readily absorb by human body, its not essential fo human body but may influence in metabolism and intake may be mildly toxic. Lithium chloride use may be dangrouse.
Lithium Carbonate at 10mg/l in blood may be mildly toxic, 15mg/l may be experience as confusion speech problem, 20mg/l has risk of lethality.
lithium contact like alkali metals may cause internal blistering.
Literature and the other elements and their interaction with water
12- Magnesium (Mg)
and water Magnesium in water (Mg + H2O)
Magnesium:
In sea water about 1300 ppm.It is the next after sodium commonly found as cation in oceans. In rivers 4 ppm. Marine contain 6000-20,000 ppm, oysters 1200 ppm. Alkali metals like sodium, potasium magesium and lithium generally causes hardness in water and if found in exessive amount make the water hard and low amount called soft water. Magnesium reacts with water vapor to magnesium hydroxide and hydrogen gas:
Mg (s) + 2H2O(g) -> Mg(OH)2(aq) + H2(g)
Water could not extinguish magnesium fire, its fire may continues even without Oxygen and react with nitrogen from atmospher forming magnesium nitride (Mg3N2) so to extinguish fire magnesium should be covered with sand.
With phosphorous magnesium form manesium phosphide (Mg3P2) solid, when contact with water or moist air decompose to phosphine(PH3)which is toxic and flammable in air.
Magnesium present mostly as Mg2+ and MgOH+and also found as MgSO4 in sea water.
Magnesium Hydroxide solubility is 12 mg/land other compounds more soluble,
.Solubility of magnesium carbonate: 600 mg/l, Magnesium sulphate is bitter to water and solubility is 309 g/l at 10oC
Magnesium minerals like dolomite (calcium magnesium carbonate CaMg(CO3)2, Magnesite(Magnesium carbonate: MgCO3), its a rock wash end up in water.
Magnesium being used in many different ways, - Magnesium being added in plastic
- Magnesium use as filler in fire protection
- in cattle field as fertilizer. - Magnesium sulphate use in beer reweries - Magnesium hydroxide used in wastewater treatment plant as a flocculant. - Its used as mild laxative. - Magnesium alloy used in in cars and plane bodies
- Magnesium extracted from sea water was used as bomb fire in 2nd world war
It is dietary mineral for live organism except insects.Chlorophyll molecule contain magnesium as as a central atom for photosynthesis.Its not found in sea water but found in river through rain and spread into the environment.
Magnesium have three natural isotops stable but not radioactive and also have 8 instable isotopes
In drinking water,any negative to human and animal health effects not expected.
Indirectly, because of water hardness cause by magnesium, Calcium negatively influence cleansing power of detergents as of formimg insoluble salts with soap, so 40 % softener is added to soap in the form of phosphate which is hardly biodegradable causing eutrophication.To avoid this other chemicals like sodium citrate, EDTA, NTA or ion exchanges like zeolite are mostly applied which do not cause eutrophication and not toxic. Nitriloacetic acid (NTA) may be mutagenic and could not be remove during purification. zeolite increases sludge. Other agent like EDTA have audacity to remove metals and difficult to decompose so metals remains in water and EDTA itself difficult to remove during purification and calcium and magnesium do not bond with zeolite under washing.
Hardness of water differs from region to region and softeners have to be added to detergents to be used as per requirement. hard water need more detergent then soft water.usage of more softner may complicate wastewater treatment process
Magnesium in human body is about 25 gm in which 60%in bones and 40% in muscles and other tissues. It is dietary for human and responsible in membrane function, nerves transmission, muscles contraction, protien production and DNA replication also essential fom many enzymes. Magnesium and calcium act nearly same in human body and is antagonistic.
Magnesium poisoning may cause because of high oral dose may cause vomiting and diarrhoea. High dose in medicine may cause muscle stackening, nerve problem,depression and personality change.
Exceeding the legal limits of magnesium in drinking water, although no scientific evidence of magnesium toxicity, in other compounds like asbestos may be harmfull.
Purification technologies:
As magnesium causes hardness in water and so it can be easily remove by water softening
Magnesium hydroxide is used as flocculant in water purification.
13. Nickel (Ni) and water
Nickel in seawater: 0.5- 2ppb -
in rivers 0.3ppb
in phytoplankton 1 - 10ppm as drymass,
in bentic algae of fresh water or salt water 0.2-84ppm, in lobsters 0.14 - 60 ppm, in molluscs 0.1 - 850ppm, in fishes 0.1 - 11ppm, In water found as Ni2+ and some time as NiCO3 as dissolved or complexed inorganic compound also bounded with particles.
On 20oC pressure 1 bar it is insoluble in waterbut most of the nickel compounds are water soluble like nickel chloride solubility = 553gm/l to 880gm/l at 99.9oC, nicle carbonate solubility = 90mg/l, other nickel compounds like nicle oxide, nickel sulphate and nickel tetra carnonyl are insoluble in water.
Nickel found in minerals like slate, sand stone, clay minerals and basalt. the main source is pentalandite, its a part of various biological cycles and accumolate in sediments.
Nickel diffusion may take place in power plants, waste incineraters and metal industries. it is directly emmited in various industeries by discharge on surface water. In alloys used for treatment of heavy metal polluted water, used in nickel -cadmium batteries, used as catalyser in pigments, pure nickel used for coatin on steel and copper parts, nickel-copper alloy used in coins, other alloys are often used for kitchen wares, jewelry and turbine and other alloys used for anti-corrosive. Nickel acetate used in textile printing, nickel carbonate for fat hardening and ceramic paints In nickel cleansing, Nickel chloride, nickel tetra carbonyl produces as by-product and applied in several production process.
In phosphate fertilizer although having traces of nickel used in agriculture. Near the fossil fuel industries the agricultural soil often have nickel in soil, normally organic matter absorb nickel so coal and oil have traces of nickel. It may be found in sludge, fly ashes fron waste incinerators. It is useful for waste separation and is 60% recyclable.
Although nickel is a dietary for living organism but excessive dose may be toxic. Metalic nickel and some of its compounds are teratogenic and carcinogenic to mammals. Normally in plants it is usually 1 μg/g, but above 50 μg/g are toxic
In dry tea leaves it is 7.6 mg/kg
Nickel between0.5 to 10 ppm reduce or stop algae growth. Fisheses normally less effective but have didderent effects in different species like: for Daphnia 30 to 150 ppb is toxic, the LD50 in lobsters lies between 150 - 300 ppm. In birds living off the water nickel found 0.6 - 36 ppm as dry mass
In rates nickel accumolate in lungs and concentration upto 4 to 40 times than others.
About 70 species of plants could get concentration up to 10,000ppm while in regular plant seed 0.5 - 2 ppm is considered as toxic. Most of the plants have nickel tolerance,but mainy species grains are susceptible and usualy die if nickel in water goes upto 40 ppm. Presence of lime in soil reduce nickel uptake. High nickel may throng heavy metals. Sludge having 200 ppm nickel as dry mass may not be used in agricultural soil.
Nickel has five natural and stable isotops and 8 ithers are instable.
The human body contain about 10 mg nickel and its a dietary requirement of most living organisms. in human body 150 μg intake utilize only 5 μg. Probably its function in urea to ammonia conversion to urea enzyme and no use in digestive system except some of its complexes. Nickel inhaling has more risk than in water and may cause lung cancer or nasal tumer. Nickel carcinogenity may be due tp nickel replacing zinc and magnesium on DNA polymerase, such thing usually found in the people working on Nickel or smoking may be one of the causes.
Dermatitis may cause due to skin contact with nickel or its solution. Nickel allergies are more common in women than men.In high concentration of nickel compounds even insoluble are more toxic like nickel tetra carbonyl although insoluble but may cause as carcenogenic. high dose intake may cause vomiting which may be for removal
Purification technologies:
Nickel can be removed by activated carbon and also by coagulation. Also by precipitation at pH 9.5 nickel fully converted to Nickel hydroxide.
This is the end of Part three. Come back later for the next Part.
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References: taken from Lenntech
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