Efficient Removal of Rhodamine B Using 1,2-Diaminoethane-modified Wheat Straw: Adsorption Performance and Mechanism

The widespread use of non-biodegradable and toxic dyes like Rhodamine B (RhB) necessitates sustainable wastewater treatment solutions. This study developed a cost-effective adsorbent by chemically modifying wheat straw with 1,2-diaminoethane. The resulting 1,2-diaminoethane-modified wheat straw (EWS) was characterized by Fourier-transform infrared spectroscopy, X-ray powder diffraction, and point of zero charge analysis. The adsorption performance was systematically evaluated under different conditions, such as pH, adsorbent dosage, temperature, and dye concentration. The adsorption mechanisms were elucidated through isotherm, kinetic, and thermodynamic studies. EWS demonstrated a 3.07-fold increase in RhB adsorption capacity (15.56 mg·g^-1) compared to natural wheat straw (5.07 mg·g^-1) under the same experimental conditions. With a Langmuir maximum adsorption capacity of 37.67 mg·g^-1 at 318 K, the process was identified as endothermic and monolayer in nature. The adsorption followed pseudo-second-order kinetics and intraparticle diffusion modeling, suggesting a chemisorption-dominated, multi-step mechanism. EWS maintained 75% efficiency after three regeneration cycles using 1.0 M NaOH as the eluant. The modification with 1,2-diaminoethane introduced amino and amide groups, which enhanced the affinity for RhB through electrostatic interactions and chemical bonding. EWS exhibits significant potential as a sustainable and cost-effective adsorbent for wastewater treatment applications, contributing to the goals of clean water and responsible resource management.