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high power as pump is utilized for the operation which makes the process uneconomical for wastewater treatment.
Nanofiltration is considered as one of the most efficient processes among the
membrane filtration processes. It was found as the efficient process for removal of
Cr (VI) (Muthukrishnan and Guha 2008), Ni(II) (Murthy and Chaudhari 2008), and
Cu(II) (Csefalvay et al. 2009; Ahmad and Ooi 2010). The literature review suggests
it was utilized for rejection of smaller particles of arsenic also (Nguyen et al. 2009;
Figoli et al. 2010). The nanofiltration is nowadays a very effective method because
of its higher efficiency and low energy requirement (Erikson 1988). Researchers
utilized NF90 and N30F resins in this process for the treatment of arsenic-loaded
water (Figoli et al. 2010). Others (Murthy and Chaudhari 2008) used composite
polyamide membrane, and 98% Ni(II) was removed. Other group of researchers
(Murthy and Chaudhari 2009) utilized nanofiltration for binary mixture of cadmium
and nickel at a concentration of 5 mg/L, and the removal percentages were 98.94%
and 82.69%, respectively. Nanofiltration and reverse osmosis were also effective for
copper removal (Csefalvay et al. 2009). Treatment of metal-contaminated effluent
coming out from metallurgical industry was done using this method by Liu and his
group (Feini et al. 2008). The literature study suggests that for the recovery of the
precious metal like silver, nanofiltration or reverse osmosis was utilized (Koseoglu
and Kitis 2009).
14.3.4 Coagulation and Flocculation
It is another useful choice for heavy metal remediation. In this process, various
coagulants such as ferrous sulfate and aluminum sulfate are utilized. Researchers
used poly-aluminum chloride to remove the toxic heavy metals (El Samrani et al.
2008). In this process, doses of coagulants are optimized on the basis of the concentration of the impurities. Chang and Wang utilized polyethyleneimine for this purpose (Chang and Wang 2007). In flocculation process, the impurities are separated
by filtration or flotation process. The recent research trend utilizes polyacrylamide
and polyferric sulfate in flocculation process. Various flocculants were reported in
literature where these were utilized for the removal of metal ion.
14.3.5 Flotation
Flotation is an important treatment method and is widely used in large-scale application. In this process, the metal is removed through bubble which is floated over
the solution. For the flotation, sometimes air is introduced to the solution, and sometimes precipitation and flotation are used. Here, metals are attached with the microbubbles, and due to lower density, it floats. The floating bubbles bearing metal ion
are separated as sludge (Lundh et al. 2000). The researchers were using the flotation
S. Biswas and S. Nag
high power as pump is utilized for the operation which makes the process uneconomical for wastewater treatment.
Nanofiltration is considered as one of the most efficient processes among the
membrane filtration processes. It was found as the efficient process for removal of
Cr (VI) (Muthukrishnan and Guha 2008), Ni(II) (Murthy and Chaudhari 2008), and
Cu(II) (Csefalvay et al. 2009; Ahmad and Ooi 2010). The literature review suggests
it was utilized for rejection of smaller particles of arsenic also (Nguyen et al. 2009;
Figoli et al. 2010). The nanofiltration is nowadays a very effective method because
of its higher efficiency and low energy requirement (Erikson 1988). Researchers
utilized NF90 and N30F resins in this process for the treatment of arsenic-loaded
water (Figoli et al. 2010). Others (Murthy and Chaudhari 2008) used composite
polyamide membrane, and 98% Ni(II) was removed. Other group of researchers
(Murthy and Chaudhari 2009) utilized nanofiltration for binary mixture of cadmium
and nickel at a concentration of 5 mg/L, and the removal percentages were 98.94%
and 82.69%, respectively. Nanofiltration and reverse osmosis were also effective for
copper removal (Csefalvay et al. 2009). Treatment of metal-contaminated effluent
coming out from metallurgical industry was done using this method by Liu and his
group (Feini et al. 2008). The literature study suggests that for the recovery of the
precious metal like silver, nanofiltration or reverse osmosis was utilized (Koseoglu
and Kitis 2009).
14.3.4 Coagulation and Flocculation
It is another useful choice for heavy metal remediation. In this process, various
coagulants such as ferrous sulfate and aluminum sulfate are utilized. Researchers
used poly-aluminum chloride to remove the toxic heavy metals (El Samrani et al.
2008). In this process, doses of coagulants are optimized on the basis of the concentration of the impurities. Chang and Wang utilized polyethyleneimine for this purpose (Chang and Wang 2007). In flocculation process, the impurities are separated
by filtration or flotation process. The recent research trend utilizes polyacrylamide
and polyferric sulfate in flocculation process. Various flocculants were reported in
literature where these were utilized for the removal of metal ion.
14.3.5 Flotation
Flotation is an important treatment method and is widely used in large-scale application. In this process, the metal is removed through bubble which is floated over
the solution. For the flotation, sometimes air is introduced to the solution, and sometimes precipitation and flotation are used. Here, metals are attached with the microbubbles, and due to lower density, it floats. The floating bubbles bearing metal ion
are separated as sludge (Lundh et al. 2000). The researchers were using the flotation
S. Biswas and S. Nag