Eosin Yellow Dye Adsorption from Aqueous Solution Using Native Maize Husk

Abstract

This work examines the uptake of Eosin Yellow (EY), an anionic dye, from aqueous solution using native maize (Zea mays) husk (MH) as a biosorbent. The biomass was characterized using Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), revealing a mesoporous structure and the presence of hydroxyl, carboxyl, and aromatic functional groups. Batch adsorption experiments were performed to assess the effects of contact time, pH, initial dye concentration, and adsorbent dosage. Maximum removal efficiency of 90.3% was attained at 1.5 g adsorbent dosage, pH 2, and 60-min contact time. The Langmuir isotherm best described the equilibrium data (R² = 0.957), with a maximum adsorption capacity of 44.5 mg g⁻¹. Kinetic data were adequately described by multiple empirical models, suggesting complex uptake behavior; however, no single rate-controlling mechanism was definitively established. Information from thermodynamic constants (ΔG° < 0, ΔH° = 21.0 kJ mol⁻¹, ΔS° = 9.25 J mol⁻¹ K⁻¹) signify that the adsorption process was spontaneous and endothermic, with features consistent with physisorption. Regeneration investigations revealed that the adsorbent retained appreciable performance over multiple cycles. These results revealed that maize husk is a promising biosorbent for dye removal under controlled laboratory conditions, although further studies are required to assess its performance in complex wastewater systems and at larger scales.