Adsorptive removal of neutral red dye from aquatic environments: a review of adsorbent materials, kinetics, isotherms, thermodynamics and future prospects

• Published in: Environmental Technology Reviews
• Main Author: Imam S.S.; Hamza M.F.
• Format: Review
• Language: English
• Published: Taylor and Francis Ltd. 2025
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85217861890&doi=10.1080%2f21622515.2025.2458090&partnerID=40&md5=9aae8b0b93ceedfbb0106447bfd99566

Due to their continuous usage, thousands of tonnes of dyes are annually released into water bodies, resulting in water pollution. Neutral red (NR) dye is widely used in research and as a tracer in the textile industry. Unfortunately, NR dye is toxic and carcinogenic. Thus, it is necessary to treat wastewater polluted by NR dye before discharge. Among the decontamination strategies available, adsorption is considered facile with low cost. The present review article explores the elimination of NR dye using various adsorbents, with a maximum adsorption capacity of 3866 mg/g achieved at pH 7 using carbon nano-onions. The effects of various operational parameters have been discussed. In addition, isotherms, kinetics, thermodynamics, mechanism, regeneration, and reusability have also been discussed. The uptake of NR dye usually fits either Langmuir or Freundlich’s isotherm model along with the pseudo-second-order kinetic model. ΔG° values for the adsorption of NR dye are usually below zero while ΔS° values are usually greater than zero. In addition, ΔH° values are of any thermic nature (endothermic/exothermic). The few studies reporting the desorption of NR dye from various adsorbents revealed high efficiency using ethanol-based desorbing agents. Such findings will guide researchers on the opportunities and challenges of various adsorbents towards remediating wastewater polluted by NR dye via adsorption. Furthermore, future prospects have been provided to aid towards filling the research gaps of novel adsorbent development, competitive studies, and continuous/column studies, including the employment of AI tools such as neural networks, fuzzy inference systems, etc. in adsorption works involving NR dye. © 2025 Informa UK Limited, trading as Taylor & Francis Group.