WATER HARDNESS
Hard water is
water that has high mineral content (in contrast with “ soft water”) hard water
is generally not harmful to ones health, but can pose serous problems in
industrial settings, where water hardness is monitored to avoid costly breakdowns
in boilers calling towards, and other equipment that handles water. In domestic
settings, hard water is often indicated by a lack of suds formation when soap
is agitated in water. Wherever water hardness is a concern, water softening is
commonly used to reduce had waters adverse effects.
SOURCES OF HARDNESS
Waters hardness
is determined by the concentration of multivalent cations in the water
multivalent cations are cations (positively charged metal complexes with a
charge greater than +1 usually, the cations have the charge of 2+. Common
cations fount in hard water include Ca2+ and Mg2+. These ions enter
a water supply by leaching from minerals with an aquifer. Common calculus containing minerals are
calcite and gypsum. A common magnesium
mineral is dolomite (which also contain calcium) rain water and distilled water
are soft, because they also contain few ions.
TEMPORARY HARDNESS
Temporary
hardness is a type of water hardness caused by the presence of dissolved
carbonate minerals (calcium carbonate). When dissolved these minerals yield
calcium and magnesium (Ca2+mg2+)
and carbonate and bicarbonate anions (CO23-HCO3)
the presence of the metal cations makes the water hard. However on like the
permanent hardness caused by sulfate and chloride compounds, this “ temporary”
hardness can be reduced either by building the water, or by the addition of
line (calcium hydroxide) through the process of lime softening boiling promotes
the formation of carbonate from the bicarbonate and precipitates calcium
carbonate out of solution, leaving water that is softer upon cooling.
PERMANENT HARDNESS
Permanent hardness is
hardness (mineral content) that cannot be removed by boiling. When this is the
case, it is usually caused by the presence of calcium and magnesium sulphates
and /or chlorides in the water, which become more soluble as the temperature
increases. Despite the name, the hardness of the water can be easily removed
using water softer or 10m exchange column.
EFFECTS
OF HARD WATER
With hard water, soap
solution’s from a white precipitates (soap scum) instead of producing lather;
this effect arises because the 2+ ions destroy the surfactant properties of the
soap by forming a solid precipitate (the soap scum). A major component of such
scum is calcium stearate, which arises from sodium stearate, this mash
component of soap.
Hardness can this be
defined as the soap consuming capacity of a water sample, or the capacity of
precipitation of soap as a characteristic property of water that prevents the
lathering of soap. Synthetic detergents do not form such scums.
METHODS
OF SOFTENING WATER
1.
Water softening methods mainly rely on the removal of
Ca2+ and Mg2+ from a solution or the
sequestration of these ions i.e. binding them to a molecule that removes their
ability to form scale or interfere with soap.
Removal is achieved by
ion exchange and by precipitation methods. Sequestration entails the addition
of chemical.
Compound
called sequestration (or chelating agents) since ca2+ and Mg2+ exist as non-volatile
salts, they can be removed by distillation.
2.
The use of ion exchange resin derives ion –exchange materials contain sodium ion
(Na+) that are electrostatically bound and that readily are replaced
by hardness ions such as Ca2+ and Mg2+. Ion exchange
resins are organic polymers containing anomic functional groups to which the Na+
is bound. Minerals called zeolites also exhibit ion- exchange properties: These minerals are widely used in laundry
detergents
3.
Lime Softening:
Chelators are use used in chemical analysis as water softeners, and are
ingredients in many commercial products such as shampoos and food preservative.
Citric acid is used to soften water in soaps and laundry detergents.
A commonly use synthetic chelator is EDTA. These are alterative to water
softening
i.
Ion exchange
ii.
water purification
iii.
Descaling agent.
DIFFERENCES BETWEEN SOFT WATER AND HARD WATER
Hard water is
water that contains an appreciable
quantify of dissolved minerals like (calcium and magnesium)
Soft water is
treated water in which only ion is sodium
The hard water
is that which does not
lather with soap while
soft water is water that lather with soap