Dyes and their removal technologies from wastewater: A critical review

Today dyes, highly colored organic compounds, find widespread applications in industries like textile, food technology, leather tanning, paper, etc., for coloring products, light-harvesting solar cells, photoelectrochemical cells, etc. However, large usage of these dyes leads to their release as effluents that eventually contaminate drinking water sources and hampering the ecological system. The contaminated wastewater effluent exhibits detrimental effects related to human beings and environmental concern. Thus, the requirement for suitable cost-effective treatment methods for contaminated wastewater seems to be indispensable. To date, there are various treatment technologies that can be roughly categorized into three types: biological, physical, and chemical methods. Bear in mind that any dye depletion technique has its own merits and demerits; therefore, a combinatorial treatment method can be advantageous. Moreover, the role of nanotechnology in the dye degradation or removal process has been marked as a promising technique in comparison to existing processes. This chapter aims to compose various information about dye, dye effluent, and existing treatment technologies for wastewater.