clean and fresh water that is adequate for human consumption. There are several
techniques/methods used to try remedy the impact by the removal of pollutants in
water. The widely explored techniques include reverse osmosis, membrane filtration,
adsorption, and disinfection (Zhao et al. 2011). Unfortunately, these techniques
display some limitations during the removal process. Some of the identified limitations include high operational costs, generation of secondary pollution, and the
inefficiency at low concentration (Zhao et al. 2011). Recently, advanced oxidation
processes (AOPs) such as photo-Fenton, heterogenous photocatalysis, sonolysis,
ozonation, as well as their combined procedures displayed great potential as solutions for the removal of organic toxins from wastewater Zhao et al. 2011; Chen and
Wang 2006; Fu and Wang 2011; Crini and Lichtfouse 2019). These methods have
showed improved efficiency for decomposing and mineralising organic toxins at
lower concentrations without the generation of secondary pollution. AOPs proceed
through the formation of reactive free radicals of OH which act as oxidising agents
towards organic pollutants, and thus forming carbon dioxide, water and inorganic
mineral salts. Heterogeneous photocatalysis that employs metal oxides such as TiO 2 ,
WO 3 , CdS and ZnO as semiconductor starts to gain a great deal of attention due to its
unique characteristics such as the ability to operate at ambient temperature and
pressure, being environmental friendly and their low energy band gap. As much as
this technique holds some good promise for application in wastewater treatment, its
popularity is sometimes quenched by the fact that it has limitations such as the less
conversion efficiency of solar energy and difficulty in separation suitable for recyclability. These limitations greatly affect the real-life environmental implementation
of this technique for applications in wastewater treatment. Hence, metal organic
frameworks, MOFs, (with their tuneable structures that can attain such high surface
area), are the sort after materials to enhance the catalytic activity of metal oxides.
Another added advantage of MOFs is that these porous crystalline materials display
features of semiconductors when exposed to light. Meaning that, MOFs possess the
light harvest properties like that of a photocatalyst. In this chapter, the recent
developments and advances of photocatalysis for wastewater treatment are summarized. This is achieved by doing comprehensive review focusing on the understanding of reactions mechanisms involved in wastewater treatment with the primary
objective being on photodegradation of organic dyes. Then, we introduce the role of
metal-organic framework (MOF) as a photocatalyst for wastewater treatment. Furthermore, we describe the challenges and approaches faced by MOF and highlights
on the recent studies which are on addressing the limitation encountered by MOF.
Finally, a detailed summary is provided to provide future perspective on using MOF
as a photocatalyst in wastewater treatment.
10 Photocatalytic Degradation of Dyes in Wastewater Using Metal Organic Frameworks 263
techniques/methods used to try remedy the impact by the removal of pollutants in
water. The widely explored techniques include reverse osmosis, membrane filtration,
adsorption, and disinfection (Zhao et al. 2011). Unfortunately, these techniques
display some limitations during the removal process. Some of the identified limitations include high operational costs, generation of secondary pollution, and the
inefficiency at low concentration (Zhao et al. 2011). Recently, advanced oxidation
processes (AOPs) such as photo-Fenton, heterogenous photocatalysis, sonolysis,
ozonation, as well as their combined procedures displayed great potential as solutions for the removal of organic toxins from wastewater Zhao et al. 2011; Chen and
Wang 2006; Fu and Wang 2011; Crini and Lichtfouse 2019). These methods have
showed improved efficiency for decomposing and mineralising organic toxins at
lower concentrations without the generation of secondary pollution. AOPs proceed
through the formation of reactive free radicals of OH which act as oxidising agents
towards organic pollutants, and thus forming carbon dioxide, water and inorganic
mineral salts. Heterogeneous photocatalysis that employs metal oxides such as TiO 2 ,
WO 3 , CdS and ZnO as semiconductor starts to gain a great deal of attention due to its
unique characteristics such as the ability to operate at ambient temperature and
pressure, being environmental friendly and their low energy band gap. As much as
this technique holds some good promise for application in wastewater treatment, its
popularity is sometimes quenched by the fact that it has limitations such as the less
conversion efficiency of solar energy and difficulty in separation suitable for recyclability. These limitations greatly affect the real-life environmental implementation
of this technique for applications in wastewater treatment. Hence, metal organic
frameworks, MOFs, (with their tuneable structures that can attain such high surface
area), are the sort after materials to enhance the catalytic activity of metal oxides.
Another added advantage of MOFs is that these porous crystalline materials display
features of semiconductors when exposed to light. Meaning that, MOFs possess the
light harvest properties like that of a photocatalyst. In this chapter, the recent
developments and advances of photocatalysis for wastewater treatment are summarized. This is achieved by doing comprehensive review focusing on the understanding of reactions mechanisms involved in wastewater treatment with the primary
objective being on photodegradation of organic dyes. Then, we introduce the role of
metal-organic framework (MOF) as a photocatalyst for wastewater treatment. Furthermore, we describe the challenges and approaches faced by MOF and highlights
on the recent studies which are on addressing the limitation encountered by MOF.
Finally, a detailed summary is provided to provide future perspective on using MOF
as a photocatalyst in wastewater treatment.
10 Photocatalytic Degradation of Dyes in Wastewater Using Metal Organic Frameworks 263