Removal of sodium dodecyl benzene sulfonate using bagasse fly ash and surface functionalized modified fly ash from aqueous solutions

Abstract

This study explores the efficacy of a cost‐effective, functionalized adsorbent derived from bagasse fly ash (FA) for the removal of the surfactant sodium dodecylbenzene sulfonate (SDBS) from aqueous solutions. The raw bagasse FA underwent a modification process involving reflux with TiO2 in NaOH at 100°C for 24 h, resulting in a modified fly ash (MFA). Comparative analyses of the sorbents were conducted using scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X‐ray diffraction (pXRD), Brunauer–Emmett–Teller (BET) surface analysis, and Fourier‐transform infrared spectroscopy (FT‐IR). The surface area of the original FA was found to be 10.795 m2 g−1, which increased to 30.597 m2 g−1 postmodification. Similarly, the crystallinity of FA was initially 49.36% and enhanced to 79.70% after the modification process. The adsorption process of SDBS onto both FA and MFA were found to follow pseudo‐second‐order kinetics. Moreover, the Langmuir adsorption isotherm was the most fitting model, as evidenced by the R2 values at 298 K for SDBS‐FA (0.99) and SDBS‐MFA (0.99), both of which are remarkably close to unity. The dimensionless separation factor (RL) was determined to be less than one, indicating favorable adsorption. The maximum adsorption capacities predicted by the Langmuir model are 156.00 mg/g for FA and a notably higher 231.48 mg/g for MFA. Thermodynamic analysis revealed a positive change in enthalpy (ΔHo) for SDBS‐FA and SDBS‐MFA of 54.50 and 124.48 KJ mol−1, respectively, suggesting endothermic adsorption. Additionally, the Gibbs free energy (ΔGo) was negative for both SDBS‐FA and SDBS‐MFA, suggesting that the adsorption of SDBS is spontaneous.