Surface modification of natural clay with H₂O₂ for high adsorption of acid Red 114: Experimental and modelling studies

The water contamination problem caused by dyes and the understanding of their adsorption mechanism in aqueous media is still significant nowadays. This study investigates the adsorption performance of natural montmorillonite clay treated with H₂O₂ (MMT-H₂O₂) and employed as an adsorbent to remove Acid Red 114 (AR-114) from aqueous solutions. MMT-H₂O₂ and the natural clay without treatment (MMT) were analysed using different analytical techniques such as XRF, XRD, FESEM, EDS, FTIR, TGA/DTG, N₂-adsorption/desorption curves, CHNS/O analysis, hydrophobicity Index (HI). It also provides a theoretical analysis of the adsorption phenomenon utilising Statistical Physics methods to understand the adsorption mechanism between AR-114 and MMT-H₂O₂ adsorbent associated with batch adsorption conditions and adsorption equilibrium. The treated clay with H₂O₂ showed a higher oxygen content and a better adsorption capacity than the untreated one. The maximum adsorption capacity (Q_max) values obtained with the best-fitted model (Liu) ranged from 421.9 and 1178.5 mg g⁻¹. This high adsorption capacity for AR-114 dye can be explained by considering the remarkable characteristics of the MMTH₂O₂ material, such as high oxygen content, variety of surface functional groups, porous interlayer structure, and hydrophilicity. The computational adsorption results suggest that the AR-114 molecules adsorbed onto the surface site of the MMTH₂O₂ adsorbent in a perpendicular orientation. This indicates that the n₂ values increased as the operating temperature was raised, demonstrating the endothermic accumulation of dye molecules on the treated clay mineral surface. Moreover, the temperature-dependent adsorption energies (E₁ and E₂) levels were less than 40 kJ mol⁻¹, highlighting the primary physical interactions between AR-114 and MMTH₂O₂ clay mineral by electrostatic attraction and hydrogen bonding.