Adsorptive and photocatalytic strategies for carmoisine removal: mechanisms, material innovations, and environmental implications

Abstract

Carmoisine (CM) (also called azorubine or Acid Red 14) poses severe environmental and health risks due to its chemical stability, persistence in environment, and generation of toxic aromatic amines. Conventional treatment methods such as coagulation, oxidation, membrane filtration, and biological degradation are ineffective and can lead to secondary pollution and incomplete mineralization. Thus, adsorptive and photocatalytic processes have emerged as efficient and sustainable alternatives for CM removal. Adsorption enables rapid dye capture through surface interactions, while photocatalysis achieves complete degradation through light-induced reactive oxygen species. Their integration in adsorptive–photocatalytic composites enhances dye pre-concentration, promotes in situ degradation, and improves catalyst reusability. This review critically discusses the mechanisms, material types, and factors controlling these processes, with emphasis on the influence of surface chemistry, electronic properties, and operational conditions. It also addresses gaps in previous studies, including poor standardization, lack of real wastewater evaluation, and limited environmental assessment. The novelty of this work lies in its comprehensive analysis linking removal performance with mineralization efficiency, toxicity reduction, and scalability while proposing green synthesis and standardized evaluation approaches. Overall, this review provides a concise yet critical framework for advancing efficient, eco-friendly, and practical adsorptive–photocatalytic technologies for the removal of CM from contaminated water systems.