Current treatment technologies and mechanisms for removal of indigo carmine dyes from wastewater: A review

The release of colored wastewater from industries into surface water bodies creates undesirable consequences to the marine ecosystem and human beings owing to its pernicious effect. Indigo dyes being aromatic compounds with complex structure are one of the most important as well as the largest classes of synthetic dyes commercially employed in the textile denim dyeing process. However, being toxic and hazardous to handle, indigo dye poses a risk of permanently damaging of eyes when it comes into direct contact and can also cause perilous trouble to the respiratory tract of human beings. The manufacturing unit handling with indigo dyes incurs huge costs for this contaminated water treatment due to strict regulatory restrictions. This review is primarily focused on the recent studies dealing with the treatment of indigo dye-containing wastewater. There are various treatment methods for the removal of indigo dye including chemical degradation, bacterial decomposition, adsorption on various adsorbents, electrochemical decolorization, as well as the use of employing nanocomposite and activated low-cost charcoal materials. A brief insight into indigo dye removal mechanism and comparison among various methods of wastewater treatment along with their advantages and disadvantages are discussed alongside suggestions for further actions that might be taken into consideration for the improvement of the treatment process from both economic and technological viewpoints