In recent years, there has been a growing interest among researchers in combining experimental and theoretical approaches to elucidate interactions between adsorbates and adsorbents. This study focuses on investigating the adsorption behavior of two anionic dyes, methyl orange (MO) and congo red (CR), on a sustainable adsorbent derived from sweet detar seed shell activated carbon. Additionally,to provide an explanation for the adsorption mechanisms using Density Functional Theory (DFT) calculations. The environmentally-friendly sweet detar seed shell activated carbon is synthesized and thoroughly characterized through various analytical techniques such as FTIR, SEM and pHpzc The experimental results for adsorption equilibrium demonstrate that the adsorption of both dyes conforms well to the Freundlich adsorption model. The maximum adsorption capacities are determined to be revealing a maximum adsorption capacity of 49.02 mg g−1 for MO and 38.91 mg g−1 for CR at. Furthermore, the kinetic data fits effectively with the pseudo-second-order kinetic model for both dyes, showing a coefficient of determination (R²) close to unity and experimental qe values for MO and CR, 9.52 and 9.43 mg/g are close to calculated values 9.62 and 9.43 mg/g. Additionally, quantum chemical parameters indicate a stronger interaction between the MO molecule and adsorbent surface framework compared to CR. These computaional results are consistent with the experimental findings, underscoring the accuracy and applicability of the calculations.
