Efficient Removal of Crystal Violet and Safranin‑O Dyes Using Naturally Plant-Derived <i>Azadirachta indica</i>: A Combined Theoretical and Experimental Investigation.

This study explored the potential benefits of <i>Azadirachta indica</i> (AzI) bark as a bioremediation agent for the removal of Crystal Violet (CV) and Safranin-O (SO) hazardous dyes from aqueous solutions. AzI bark is a natural plant-based material, and its botanical name is neem. Diverse interactions between AzI bark and both dyes were assessed by experimental methods and validated using computational studies. The removal of dye using the adsorption method is recognized as a very effective technique for wastewater treatment. The batch adsorption capacity was evaluated under varying pH levels, contact times, and concentrations of the dye solution at room temperature. Theoretical approaches, including molecular docking and density functional theory (DFT) analysis, were employed to identify the types of interactions between the AzI bark, CV, and SO dye. Quantitative analysis was conducted by measuring absorbance with a UV-vis spectrophotometer at λ_max values of 591 nm for CV and 521 nm for the SO dye. The adsorption efficiency of AzI bark was determined to be 137.78 mg/g at 175 ppm and 110.56 mg/g at 150 ppm for CV and SO dye, respectively, at pH 7. The correlation coefficient (<i>R</i> ²) for the Langmuir isotherm was found to be 0.9940 for CV and 0.8671 for the SO dye. Kinetic studies showed that the pseudo-second-order reaction best fits the adsorption process, verifying the experimental isotherm and kinetic data. However, since AzI bark is a low-cost, ecofriendly, biodegradable, and widely available natural resource, it holds significant promise for application in industrial wastewater treatment. Additionally, experiments related to the remediation of CV and SO dyes from aqueous solution on AzI bark explored the impact of metal ions, such as iron, copper, and nickel, ranging from 20 to 100 ppm.