262
improved by proper physical and chemical treatment. Fly ash has been used for different applications in wastewater treatment. Mainly Cr, Pb, Ni, As, Hg, Cd, and Cu
adsorption by fly ash has been studied. Study on Zn
+2
and Ni
+2
removal ability by
activated carbon and fly ash showed that maximum metal removal depends on concentration of Zn
+2
and Ni
+2
and pH of solution (Cetin and Pehlivan 2007). Zeolite
can be synthesized from natural resources like fly ash, red mud, and clay which can
be further used as an adsorbent for treatment of wastewater. Studies on fly ashderived nano-zeolite X sono-sorptive for the elimination of methylene blue have
been done (Sivalingam et al. 2018). Maximum methylene blue removal of 64.52%
by coal fly ash, 99.30% by highly pure nanozeolite X, and 96.57% by commercial
zeolite X was achieved at a certain pH.
Red mud is also serving as good source low-cost adsorbent which is very abundant industrial waste. It is a residue of bauxite ore processing during caustic leaching in alumina production process, also known as Bayer’s process. About half tons
of red mud produced one ton of alumina. Red mud is mainly composed of aluminum, silicon oxide, calcium, and iron which are the reason behind its high surface
reactivity. Therefore they have been used widely for the extraction of heavy metals
in the treating process of wastewater. Arsenic which causes several health hazards
can be removed by red mud. Thermal and chemical modification on red mud
increases its adsorptive capacity. Like other adsorbents, red mud activity is also
dependent upon pH. As
+3
was adsorbed at alkaline pH 5.8–7.5, while As
+5
was significantly reduced at acidic pH 1.8–3.5 (Selvaraj et al. 2003). Red mud can be used
as liquid phase too for As
+5
removal, and it was proved to be more advantageous
over solid phase.
10.3.8 Bioadsorbent
Bioadsorption is a new area in the field of wastewater treatment having a high efficiency in extraction of heavy metal. The major benefits of using this process are use
of inexpensive bioadsorbent because of their natural origin as well as fast and
reversible. The three main sources of bioadsorbent are algal biomass, microbial
biomass, and non-living sources such as crab shell, lignin, shrimp shell, and bark.
The most abundantly available biosorbent on earth crust is algae. The algae or
marine algae are mostly used in different fields such as food processing and pharmaceutical applications. Owing to its remarkable adsorption capacity and renewable availability, it can be used as a promising bioadsorbent. Figure 10.2 shows the
number of documents published in the area of heavy metal removal by
biosorption.
There are three types of marine algae: green algae, brown algae, and red algae.
They consist of certain active functional groups, like amine, hydroxyl on the surface
of the cell wall which possesses chemical bond with metals, and selective binding
in the adsorption process.
M. Maharana et al.
improved by proper physical and chemical treatment. Fly ash has been used for different applications in wastewater treatment. Mainly Cr, Pb, Ni, As, Hg, Cd, and Cu
adsorption by fly ash has been studied. Study on Zn
+2
and Ni
+2
removal ability by
activated carbon and fly ash showed that maximum metal removal depends on concentration of Zn
+2
and Ni
+2
and pH of solution (Cetin and Pehlivan 2007). Zeolite
can be synthesized from natural resources like fly ash, red mud, and clay which can
be further used as an adsorbent for treatment of wastewater. Studies on fly ashderived nano-zeolite X sono-sorptive for the elimination of methylene blue have
been done (Sivalingam et al. 2018). Maximum methylene blue removal of 64.52%
by coal fly ash, 99.30% by highly pure nanozeolite X, and 96.57% by commercial
zeolite X was achieved at a certain pH.
Red mud is also serving as good source low-cost adsorbent which is very abundant industrial waste. It is a residue of bauxite ore processing during caustic leaching in alumina production process, also known as Bayer’s process. About half tons
of red mud produced one ton of alumina. Red mud is mainly composed of aluminum, silicon oxide, calcium, and iron which are the reason behind its high surface
reactivity. Therefore they have been used widely for the extraction of heavy metals
in the treating process of wastewater. Arsenic which causes several health hazards
can be removed by red mud. Thermal and chemical modification on red mud
increases its adsorptive capacity. Like other adsorbents, red mud activity is also
dependent upon pH. As
+3
was adsorbed at alkaline pH 5.8–7.5, while As
+5
was significantly reduced at acidic pH 1.8–3.5 (Selvaraj et al. 2003). Red mud can be used
as liquid phase too for As
+5
removal, and it was proved to be more advantageous
over solid phase.
10.3.8 Bioadsorbent
Bioadsorption is a new area in the field of wastewater treatment having a high efficiency in extraction of heavy metal. The major benefits of using this process are use
of inexpensive bioadsorbent because of their natural origin as well as fast and
reversible. The three main sources of bioadsorbent are algal biomass, microbial
biomass, and non-living sources such as crab shell, lignin, shrimp shell, and bark.
The most abundantly available biosorbent on earth crust is algae. The algae or
marine algae are mostly used in different fields such as food processing and pharmaceutical applications. Owing to its remarkable adsorption capacity and renewable availability, it can be used as a promising bioadsorbent. Figure 10.2 shows the
number of documents published in the area of heavy metal removal by
biosorption.
There are three types of marine algae: green algae, brown algae, and red algae.
They consist of certain active functional groups, like amine, hydroxyl on the surface
of the cell wall which possesses chemical bond with metals, and selective binding
in the adsorption process.
M. Maharana et al.