250
et al. 2004). Among the varieties of ion-exchange resins, the most common cation
exchangers like sulfonic acid groups containing resins are strongly acidic and carboxylic acid groups contaning resins are weakly acidic. Dowex 50 W is one such
resin which contains RSO 3
–
group and was applied for removing of cadmium ions
from aqueous solutions (Pehlivan and Altun 2006). The disadvantages include very
high cost of ion exchange resin and partial removal of certain ions.
10.2.3 Membrane Filtration
Membrane filtration is very simple and easy technique to remove various heavy
metals by using various membranes. This process mainly depends on particle size.
This technique is used in different forms which are described as the following.
Ultrafiltration
Ultrafiltration technique uses a semipermeable membrane to eliminate dissolved
molecules and metal ions in low transmembrane pressure based on molecular size.
The membrane offers passage for low molecular solutes and separates out the larger
molecules and heavy metals. Ultrafiltration technique is of three types: complexation – ultrafiltration, micellar enhanced ultrafiltration, and chelating enhanced
ultrafiltration. Chitosan and synthetic carboxymethyl cellulose both have strong
influence on enhancement of nickel rejection provided that adequate amount of
polymer is used. Amicon YM10 Ultracel regenerated cellulose which was applied
as the ultrafilter, is highly efficient in removal of copper and zinc ions at a high pH
8.5–9 (Juang and Shiau 2000). These experiments revealed that heavy metal elimination ability is enhanced by using chitosan ultrafiltration membranes. Large
amount of production of sludge is the main limitation of this technique as it is tough
to manage such huge amount.
Nanofiltration
Nanofiltration is the in-between process between ultrafiltration and reverse osmosis.
It is an efficient technique for the separation of heavy metal ions such as Ni
+2
, Cr
+6
,
Cu
+2
, and As
+3
from wastewater. Advantages of nanofiltration process are simple
operation, consistency, low energy consumption, and high pollutant removal efficiency. In nanofiltration, soluble elements cannot be separated from the water,
which is a major limitation of this process.
M. Maharana et al.
et al. 2004). Among the varieties of ion-exchange resins, the most common cation
exchangers like sulfonic acid groups containing resins are strongly acidic and carboxylic acid groups contaning resins are weakly acidic. Dowex 50 W is one such
resin which contains RSO 3
–
group and was applied for removing of cadmium ions
from aqueous solutions (Pehlivan and Altun 2006). The disadvantages include very
high cost of ion exchange resin and partial removal of certain ions.
10.2.3 Membrane Filtration
Membrane filtration is very simple and easy technique to remove various heavy
metals by using various membranes. This process mainly depends on particle size.
This technique is used in different forms which are described as the following.
Ultrafiltration
Ultrafiltration technique uses a semipermeable membrane to eliminate dissolved
molecules and metal ions in low transmembrane pressure based on molecular size.
The membrane offers passage for low molecular solutes and separates out the larger
molecules and heavy metals. Ultrafiltration technique is of three types: complexation – ultrafiltration, micellar enhanced ultrafiltration, and chelating enhanced
ultrafiltration. Chitosan and synthetic carboxymethyl cellulose both have strong
influence on enhancement of nickel rejection provided that adequate amount of
polymer is used. Amicon YM10 Ultracel regenerated cellulose which was applied
as the ultrafilter, is highly efficient in removal of copper and zinc ions at a high pH
8.5–9 (Juang and Shiau 2000). These experiments revealed that heavy metal elimination ability is enhanced by using chitosan ultrafiltration membranes. Large
amount of production of sludge is the main limitation of this technique as it is tough
to manage such huge amount.
Nanofiltration
Nanofiltration is the in-between process between ultrafiltration and reverse osmosis.
It is an efficient technique for the separation of heavy metal ions such as Ni
+2
, Cr
+6
,
Cu
+2
, and As
+3
from wastewater. Advantages of nanofiltration process are simple
operation, consistency, low energy consumption, and high pollutant removal efficiency. In nanofiltration, soluble elements cannot be separated from the water,
which is a major limitation of this process.
M. Maharana et al.