fabricated a number of sponges and fabrics formed upon growing of nanocrystals of
transition metals and metal oxides, with further modification by thiol. The metal
oxides used were that of copper, nickel, cobalt and iron. The fabricated fibers
possessed superhydrophibic/superoleophilic surface wettability, and were found to
be effective to remove both light and heavy oils. On the other hand, the fabricated
sponges possessed very high adsorption capacities, selectivity and recyclability.
1.6 Fluoride
Below the prescribed concentration, intake of fluoride is beneficial to our bodies.
However, if taken above the safe limit, fluorides can seriously affect our bones and
teeth in the form of fluorosis, cause damage to our brain and kidney, as well as affect
the metabolism of elements in our body and cause neurological damage. Fluoride
gets added to the surface and groundwater via effluents from industries, including
fertilizer, semiconductor, cosmetics, drugs and ceramic manufacturing plants and
power plants running on coal. Several metal oxides have been successfully used for
the purpose of decontaminating fluoride from water (Velazquez-Jimenez et al.
2015). This section is dedicated to this aspect of water treatment.
The mostly used metal oxide for defluoridation of water is aluminum oxide, either
as the sole decontaminant or in conjunction with other metal oxides. The main
advantage of using Al 2 O 3 is the fact that it possesses a very high internal surface
area; thus, a high number of adsorption sites are available for trapping contaminant
moieties. For example, Kumar et al. (2011) made us of nano-Al 2 O 3 for adsorption of
fluoride from aqueous solution and achieved a maximum adsorption capacity of
14 mgg
À1 at a pH value of 6.15 and at a temperature of 25
C. It was further noticed
that the fluoride adsorption process was influenced by the solution pH, temperature
and by the presence of other contaminating ions like phosphate, sulfate and carbonate. Table 1.2 presents the Freundlich and Langmuir isotherms of the adsorption
process at two different temperatures. It can be realized from the table that the
Langmuir isotherm model better explains the adsorption process. In another related
study with nano-AlOOH, maximum adsorption (fitting the Langmuir isotherm
model) was observed to happen at ~pH 7 and desorption at pH 13, revealing the
Fig. 1.9 Oil adsorption process by the polysiloxane-coated magnetic Fe 2 O 3 @C core-shell
nanoparticulate adsorbent, followed by complete removal of the oil-adsorbed nanoparticles with
the help of an external magnetic field. (Reprinted with permission from Zhu et al. (2010). © 2010
American Chemical Society)
14
K. Dutta
transition metals and metal oxides, with further modification by thiol. The metal
oxides used were that of copper, nickel, cobalt and iron. The fabricated fibers
possessed superhydrophibic/superoleophilic surface wettability, and were found to
be effective to remove both light and heavy oils. On the other hand, the fabricated
sponges possessed very high adsorption capacities, selectivity and recyclability.
1.6 Fluoride
Below the prescribed concentration, intake of fluoride is beneficial to our bodies.
However, if taken above the safe limit, fluorides can seriously affect our bones and
teeth in the form of fluorosis, cause damage to our brain and kidney, as well as affect
the metabolism of elements in our body and cause neurological damage. Fluoride
gets added to the surface and groundwater via effluents from industries, including
fertilizer, semiconductor, cosmetics, drugs and ceramic manufacturing plants and
power plants running on coal. Several metal oxides have been successfully used for
the purpose of decontaminating fluoride from water (Velazquez-Jimenez et al.
2015). This section is dedicated to this aspect of water treatment.
The mostly used metal oxide for defluoridation of water is aluminum oxide, either
as the sole decontaminant or in conjunction with other metal oxides. The main
advantage of using Al 2 O 3 is the fact that it possesses a very high internal surface
area; thus, a high number of adsorption sites are available for trapping contaminant
moieties. For example, Kumar et al. (2011) made us of nano-Al 2 O 3 for adsorption of
fluoride from aqueous solution and achieved a maximum adsorption capacity of
14 mgg
À1 at a pH value of 6.15 and at a temperature of 25
C. It was further noticed
that the fluoride adsorption process was influenced by the solution pH, temperature
and by the presence of other contaminating ions like phosphate, sulfate and carbonate. Table 1.2 presents the Freundlich and Langmuir isotherms of the adsorption
process at two different temperatures. It can be realized from the table that the
Langmuir isotherm model better explains the adsorption process. In another related
study with nano-AlOOH, maximum adsorption (fitting the Langmuir isotherm
model) was observed to happen at ~pH 7 and desorption at pH 13, revealing the
Fig. 1.9 Oil adsorption process by the polysiloxane-coated magnetic Fe 2 O 3 @C core-shell
nanoparticulate adsorbent, followed by complete removal of the oil-adsorbed nanoparticles with
the help of an external magnetic field. (Reprinted with permission from Zhu et al. (2010). © 2010
American Chemical Society)
14
K. Dutta