The Role and Significance of Biochars for the Photodegradation of Selected Organic Dyes in Water and Wastewater

All types of life require water to survive. Clean surface and groundwater resources are lost over time because of not only climate change and global warming, but also pollution caused by rapid population growth, unplanned urbanization, and rapid development of industrialization. Organic dyestuffs are discharged directly or indirectly into surface and groundwaters by wastes from the textile, painting, pharmaceutical, cosmetic, and cleaning material manufacturing industries without proper treatment. If polluted water containing organic dyestuff is treated to a level that allows its reuse, it can be considered an alternative freshwater resource. In this context, the focus has been given to non-conventional biomaterial adsorbent; biochar (BC). BC obtained from biological materials are easily available and highly effective adsorbents. The interactions between dyestuff and BC allow to concentrate and to remove dye molecules from wastewater. BC materials have been extensively studied and reported for water purification through biosorption and biodegradation of organic dye contamination. There is now a new family of carbons combined with nano metal oxides (n-MeO) catalysts to form an excellent removal performance for dye molecules. These hybridized nanocomposites made from BC-assisted photocatalysts showed amazing physicochemical properties and have been widely used in the degradation of water pollutants. This paper focuses on the progress and growth of research in the extensively explored n-MeO/BC based water treatment methods against dye pollution of wastewater. By combining photocatalysis and adsorption, n-MeO/BC nanocomposites have remarkable dye removal capabilities. The use of n-MeO/BC nanocomposites for wastewater treatment containing rhodamine B, methylene blue, malachite green and methyl violet 2B dye molecules and a comparison between dye removal capacity of BC and n-MeO/BC are the main topics of discussion.