There has been a considerable amount of research in the development of sustainable
water treatment techniques capable of improving the quality of water. Unavailability
of drinkable water is a crucial issue especially in regions where conventional drinking
water treatment systems fail to eradicate aquatic pathogens, toxic metal ions and
industrial waste. The research and development in this area have given rise to a new
class of processes called advanced oxidation processes, particularly in the form of
heterogeneous photocatalysis, which converts photon energy into chemical energy. Advances
in nanotechnology have improved the ability to develop and specifically tailor the
properties of photocatalytic materials used in this area. This paper discusses many
of those photocatalytic nanomaterials, both metal-based and metal-free, which have
been studied for water and waste water purification and treatment in recent years.
It also discusses the design and performance of the recently studied photocatalytic
reactors, along with the recent advancements in the visible-light photocatalysis.
Additionally, the effects of the fundamental parameters such as temperature, pH, catalyst-loading
and reaction time have also been reviewed. Moreover, different techniques that can
increase the photocatalytic efficiency as well as recyclability have been systematically
presented, followed by a discussion on the photocatalytic treatment of actual wastewater
samples and the future challenges associated with it.