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processes in removing toxic heavy metals. In dissolved air flotation process, floating
particles in the water attach to air microbubbles which further develop agglomerates
producing flocs which rise through the water and accumulate on the surface of water
and thus can be separated easily as sludge. Disadvantage of this process is its high
operating cost.
10.2.6 Phytoremediation
Phytoremediation is the process in which plants and their associated microorganisms treat pollutants in soil, water, and air. In this process, natural plants or genetically engineered plants are used to eliminate pollutants like toxic metals, antibiotics,
and pesticides. The benefits behind this technique over conventional techniques are
such that this process is cheap and environment friendly. But there are some limitations which can be overcome by using high biomass plants with faster growth rate.
Table 10.3 shows some other advantages and limitations of phytoremediation process. For environmental remediation, plants are chosen selectively which can accumulate pollutants thereby controlling pollution.
The disadvantages of this method are the following: it is a slow process, and
plant regeneration is challenging which subjects to poor heavy metal removal and
requires high energy. Also a large amount of harmful sludge is created which results
in difficulty in disposal (Feng and Aldrich 2004). Various experiments have been
done for the elimination of heavy metals from environment using variety of plant
species which is listed in Table 10.4.
10.2.7 Photocatalysis
Basically heavy metal removal involves reduction reactions from higher oxidation
state to lower one to produce elemental metals or metal ions. This mechanism is
applicable for all heavy metal ions except for arsenic, which exists in anionic form
and needs to be converted to higher oxidation state via oxidation reaction. Therefore
TiO 2 with ultraviolet radiation has the capability to endure both oxidation and
Table 10.3 Advantages and limitations of phytoremediation
Advantages
Limitations
1. Environment-friendly and cost-effective
1. Process is limited to the depth reached by
roots
2. It can treat site with more than one pollutant
type
2. It depends on the tolerance capacity of plants
used
3. Precious pollutants can be collected from
accumulating plants after end of process
3. Because of their biodegradable nature, there
is chance of reentering of heavy metals
M. Maharana et al.
processes in removing toxic heavy metals. In dissolved air flotation process, floating
particles in the water attach to air microbubbles which further develop agglomerates
producing flocs which rise through the water and accumulate on the surface of water
and thus can be separated easily as sludge. Disadvantage of this process is its high
operating cost.
10.2.6 Phytoremediation
Phytoremediation is the process in which plants and their associated microorganisms treat pollutants in soil, water, and air. In this process, natural plants or genetically engineered plants are used to eliminate pollutants like toxic metals, antibiotics,
and pesticides. The benefits behind this technique over conventional techniques are
such that this process is cheap and environment friendly. But there are some limitations which can be overcome by using high biomass plants with faster growth rate.
Table 10.3 shows some other advantages and limitations of phytoremediation process. For environmental remediation, plants are chosen selectively which can accumulate pollutants thereby controlling pollution.
The disadvantages of this method are the following: it is a slow process, and
plant regeneration is challenging which subjects to poor heavy metal removal and
requires high energy. Also a large amount of harmful sludge is created which results
in difficulty in disposal (Feng and Aldrich 2004). Various experiments have been
done for the elimination of heavy metals from environment using variety of plant
species which is listed in Table 10.4.
10.2.7 Photocatalysis
Basically heavy metal removal involves reduction reactions from higher oxidation
state to lower one to produce elemental metals or metal ions. This mechanism is
applicable for all heavy metal ions except for arsenic, which exists in anionic form
and needs to be converted to higher oxidation state via oxidation reaction. Therefore
TiO 2 with ultraviolet radiation has the capability to endure both oxidation and
Table 10.3 Advantages and limitations of phytoremediation
Advantages
Limitations
1. Environment-friendly and cost-effective
1. Process is limited to the depth reached by
roots
2. It can treat site with more than one pollutant
type
2. It depends on the tolerance capacity of plants
used
3. Precious pollutants can be collected from
accumulating plants after end of process
3. Because of their biodegradable nature, there
is chance of reentering of heavy metals
M. Maharana et al.