Adsorption and photocatalytic removal of Rhodamine B from wastewater using carbon-based materials

The removal of Rhodamine B dyes (RhB) from wastewater, using the conventional water treatment techniques, usually involves some challenging processes. This is challenging because RhB is a highly soluble and persistent dye found in wastewater. Although some efficient physiochemical techniques have been reported, the limitations associated with these technologies, such as the production of secondary wastes in the chemical precipitation process, cannot be overlooked. Photocatalysis, on the other hand, could transform the dye molecules to less toxic or non-toxic final products without the generation of secondary wastes. Therefore, the combined use of photocatalysis and adsorption processes for the removal of RhB from water has been found to be highly efficient. However, the development of materials that possess efficient adsorption and photocatalytic properties remains a major challenge since most of the known materials have a low adsorption capacity and may not be photostable. Carbon-based materials have been used as an efficient material for the removal of RhB from wastewater due to their high adsorption capacity and light-sensitive properties. In this report, the properties, synthesis and use of the carbon-based materials for the removal of RhB from wastewater are discussed in detail. Different factors that affect the removal of RhB dyes from wastewater and the mechanism of photocatalysis and adsorption isotherms are critically reviewed. Furthermore, limitations of carbon-based materials as both adsorbents and photocatalysts are presented, and the possible methods for overcoming these limitations are also investigated.