BIOSORPTION OF Pb2+, Cd2+, & Ni2+ FROM WATERS BY ...

· or the change of active conformation (form) of the biomolecule. Hence,
heavymetals can have toxicological affects on human body after some concentrations
specific for each metal.
Heavy metals are natural components of the Earth's crust. They can enter a
water supply by industrial and domestic use, and from acid rain which breaks down
soils and releases heavy metals into streams, lakes, rivers, and groundwater. They can
be deposited in human body by food, drinking water and air.
All living creatures need essential metals (Cu, Zn, Fe, Ni etc.) to maintain
their biological activities. The hazardous effects of heavy metals are the result of their
accumulation in the organism. Accumulation causes a rise in the concentration of a
chemical in a biological organism in a time interval, hence its concentration becomes
greater than its concentration in the environment. This situation makes heavy metals
dangerous for living things since chemicals are deposited in living things in any time
and are taken up quicker than they are metabolized or excreted.
1.2.1. Lead
Lead, is a soft malleable poor metal, has a bluish white colour; however, it
looses its brightness when it is exposed to air. It is found in small amounts in the
earth’s crust, but it can also be found in all parts of the environment owing to human
activities like burning fossil fuels, mining, and manufacturing. Lead has many uses in,
for example, building construction, lead-acid batteries, bullets and shot, weights,
devices to shield X-rays and it is also part of solder, pewter, fusible alloys . It is also
used in the fuel as an anti-knocking agent in methylated form (tetra-ethyl lead).
However, in most industrialized countries their environmental impact has levelled off
as legislation aimed at reducing and replacing lead in petrol.
Lead itself does not break down; nevertheless, the change of lead compounds
are due to sunlight, air, and water. Once lead is released to the air it generally binds to
dust particles and can travel long distances before reaching the soils. Mobility of lead
from soils is also based on the type of the lead compound and the characteristics of
the soil.
Lead is a pollutant that is present everywhere in the ecosystem. Lead uptake
can take place because of consumption of lead containing drinks or foods, and
through respiratory system. The lead-based paint in older homes can create a serious
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