improving adsorption and photo efficiency capacity. However, the demands of
practical application may not be met by using them, particularly for highly polluted
wastewater, due to their non-selective adsorption and low binding efficiency. Contrarily, it is established that the process of adsorption follows a dynamic equilibrium
state where surface-adsorbed moieties pervade into the absorbents until equilibrium
is achieved. Therefore, it is hard to remove contaminants completely only through
adsorption, particularly in the case of higher contaminant concentration. Uniting the
benefits of adsorbent and photocatalyst, composite materials having synergetic effect
might be able to overcome these issues. One of the best strategies is to develop
polymer surface-functionalized inorganic core–shell composite nanostructure capable of accumulating higher concentrations of contaminants on their surface and
accelerating the photocatalytic degradation process. A continuous process is developed by combining adsorption and photodegradation of contaminants accompanied
by the following steps: (i) the contaminants would efficiently bind with the surface
of absorptive polymer, and then surface-bound contaminants might pervade into
the photocatalytic core; (ii) under light illumination, the excitation of encapsulated
photocatalysts would occur, leading to photocatalytic degradation of absorbed
contaminants; (iii) the lesser contents inside polymer might result in
non-equilibrium states, and incessant adsorption occurs. Such a continuous process
of adsorption and degradation may not only completely eliminate contaminants in
limited time, but the composite photocatalysts may also be reused directly without
any additional treatment. The practical applications of this strategy involve two
major steps: first efficient adsorption of contaminants onto the polymer, leading to
a decrease in contaminant concentration; then a continuous process of adsorption
and degradation takes place until degradation completes. Although these functional
polymer-encapsulated materials exhibited attractive selectivity and adsorption capability, their method of preparation is comparatively lengthy and complex, which may
not be appropriate for upscaling. Therefore, some carbon-based materials and
several commercially available foams with low density, outstanding stretchability
and flexibility, excellent chemical stability, high surface area, and eco-friendliness
are supposed to be the best alternatives for efficient treatment of wastewater.
18.3.2 Carbonaceous Composite Materials
Carbon-based composite nanomaterials designed by using different forms of carbon,
such as graphite, graphene, and carbon nanotubes, have been extensively investigated to achieve enhanced adsorption and photocatalytic degradation under visible
light. Carbon in its activated form can effectively adsorb the pollutants, but the
recycling cost is comparatively higher. Therefore, activated carbon was used as a
support to load photocatalytically active TiO 2 for the degradation of dyes (Fu et al.
2006). In this composite, the activated carbon would aid to supplement the confined
contaminant contents of photocatalyst and consequently accelerate the process of
transfer of contaminants. Furthermore, the combined influence of photodegradation
18 Nanomaterials for Textile Waste Treatment
673
practical application may not be met by using them, particularly for highly polluted
wastewater, due to their non-selective adsorption and low binding efficiency. Contrarily, it is established that the process of adsorption follows a dynamic equilibrium
state where surface-adsorbed moieties pervade into the absorbents until equilibrium
is achieved. Therefore, it is hard to remove contaminants completely only through
adsorption, particularly in the case of higher contaminant concentration. Uniting the
benefits of adsorbent and photocatalyst, composite materials having synergetic effect
might be able to overcome these issues. One of the best strategies is to develop
polymer surface-functionalized inorganic core–shell composite nanostructure capable of accumulating higher concentrations of contaminants on their surface and
accelerating the photocatalytic degradation process. A continuous process is developed by combining adsorption and photodegradation of contaminants accompanied
by the following steps: (i) the contaminants would efficiently bind with the surface
of absorptive polymer, and then surface-bound contaminants might pervade into
the photocatalytic core; (ii) under light illumination, the excitation of encapsulated
photocatalysts would occur, leading to photocatalytic degradation of absorbed
contaminants; (iii) the lesser contents inside polymer might result in
non-equilibrium states, and incessant adsorption occurs. Such a continuous process
of adsorption and degradation may not only completely eliminate contaminants in
limited time, but the composite photocatalysts may also be reused directly without
any additional treatment. The practical applications of this strategy involve two
major steps: first efficient adsorption of contaminants onto the polymer, leading to
a decrease in contaminant concentration; then a continuous process of adsorption
and degradation takes place until degradation completes. Although these functional
polymer-encapsulated materials exhibited attractive selectivity and adsorption capability, their method of preparation is comparatively lengthy and complex, which may
not be appropriate for upscaling. Therefore, some carbon-based materials and
several commercially available foams with low density, outstanding stretchability
and flexibility, excellent chemical stability, high surface area, and eco-friendliness
are supposed to be the best alternatives for efficient treatment of wastewater.
18.3.2 Carbonaceous Composite Materials
Carbon-based composite nanomaterials designed by using different forms of carbon,
such as graphite, graphene, and carbon nanotubes, have been extensively investigated to achieve enhanced adsorption and photocatalytic degradation under visible
light. Carbon in its activated form can effectively adsorb the pollutants, but the
recycling cost is comparatively higher. Therefore, activated carbon was used as a
support to load photocatalytically active TiO 2 for the degradation of dyes (Fu et al.
2006). In this composite, the activated carbon would aid to supplement the confined
contaminant contents of photocatalyst and consequently accelerate the process of
transfer of contaminants. Furthermore, the combined influence of photodegradation
18 Nanomaterials for Textile Waste Treatment
673