BIOSORPTION OF Pb2+, Cd2+, & Ni2+ FROM WATERS BY ...
BIOSORPTION OF Pb2+, Cd2+, & Ni2+ FROM WATERS BY ...
BIOSORPTION OF Pb2+, Cd2+, & Ni2+ FROM WATERS BY ...
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determination of Se(IV) and Se(VI) was done by electrothermal atomic absorption<br />
spectrometry (ETAAS) (Robles, et al. 1999).<br />
1.3.2. Removal of Heavy Metals<br />
Heavy metals have potential risk on the environment depending on their<br />
amount and in which they exist, hence it is required to remove the heavy metals from<br />
the environment.<br />
For the removal of metal ions from aqueous streams, there are some<br />
processes that are applied commonly; reverse osmosis, electrodialysis, ion exchange,<br />
precipitation, solvent extraction, and phytoremediation.<br />
Reverse Osmosis is an expensive method in which the separation of heavy<br />
metals is achieved by a semi-permeable membrane at a pressure greater than osmotic<br />
pressure by the dissolved solids in wastewater.<br />
In electrodialysis, separation of the heavy metals (the ionic components) is<br />
performed through semi-permeable ion-selective membranes. Migration of cations<br />
and anions towards respective elctrodes takes place when an electrical potential is<br />
applied between the two electrodes. The major drawback of this method is clogging<br />
the membrane by metal hydroxide formation.<br />
Ion-exchange is a process that metal ions from dilute solutions are replaced<br />
with ions held by electrostatic forces on the exchange resin. However, this process<br />
has some disadvantages due to the fact that it has high cost and requires partial<br />
removal of certain ions.<br />
Precipitation is achieved by the addition of chemicals like as lime, iron salts<br />
and other organic polymers, and it needs the conventional solid-liquid removal by<br />
sedimentation. The production of large amount of sludge containing toxic compounds<br />
during the process is the most significiant problem of this process (Biosorption 2008).<br />
Metal contaminated soil, sediment, and water is cleaned up by the certain<br />
plants is called phytoremediation, however the removal of heavy metals takes long<br />
time and the regeneration of the plant for the next use is difficult.<br />
Up to now, the conventional methods has some disadvantages like incomplete<br />
metal(s) removal, high energy and reagent requirements, generation of toxic sludge or<br />
other waste products which makes the careful disposal of waste requisite. This also<br />
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