RSC Adv. 2026 Sep 15. doi: 10.1039/d6ra06805g. Online ahead of print.
ABSTRACT
Indigo carmine (IC) persists in aquatic environments due to its high solubility, aromatic stability, and sulfonated structure, raising toxicity concerns and inducing the formation of harmful oxidative intermediates. This review critically summarizes the information on IC and provides a mechanistic evaluation of its removal through adsorption, photocatalysis, electrochemical oxidation, biodegradation, and enzymatic treatment. Adsorption remains the superior performance and simplest decolorization method, whereas photocatalysis and advanced oxidation provide deeper degradation through radical-mediated cleavage of the chromophore and aromatic rings. Electrochemical technologies ensure rapid oxidation through direct/indirect anodic processes, while microbial and enzyme-based treatments (particularly using laccases and peroxidases) offer environmentally benign pathways for detoxification under mild conditions. A comprehensive comparison of material classes, like inorganic adsorbents (activated carbon (AC), biochar (BC), graphene derivatives, zeolites, porous silica, metal oxides, metal sulfides, and metal organic frameworks (MOFs)), organic polymers (synthetic resins, chitosan (CS), cellulose, and alginate), and biological systems (microorganisms and isolated enzymes), highlights their functional roles, advantages, and limitations. The factors enhancing the IC removal efficiency, like the solution pH, functional surface chemistry, porosity, ionic strength, catalyst doping, light utilization, hybrid systems, and process integration, are examined critically to identify optimization strategies. The main challenges remain in scaling laboratory findings to real wastewater treatment processes and understanding by-product toxicity, which, if overcome, would improve catalyst stability/regeneration and reduce energy consumption. Future perspectives emphasize the development of hybrid materials combining adsorption and catalytic properties, visible-light-active and immobilized photocatalysts, engineered enzymes, and integrated treatment trains for complete mineralization with a low environmental footprint. This review provides a holistic and analytical foundation for advancing efficient, scalable, and sustainable technologies for the removal and detoxification of indigo carmine from contaminated water.
PMID:42746161 | PMC:PMC13575971 | DOI:10.1039/d6ra06805g