Efficient dye removal from wastewater using fly ash-based adsorbents

This study explores the adsorption efficiency of two types of fly ash to remove Coomassie Brilliant Blue (CBB), an organic dye, from aqueous solutions. Batch adsorption experiments were carried out to evaluate the performance of the two fly ash samples. Fly Ash 2 demonstrated the highest adsorption capacity, achieving complete dye removal (99%) within 120 minutes. Fly Ash 2 was chemically modified to further enhance its performance using acid treatments (HCl and H₂SO₄) and a base treatment (NaOH). These modifications significantly improved the adsorption kinetics, reducing the time required for dye removal while increasing overall efficiency. Comprehensive physicochemical characterization of both unmodified and modified fly ash was performed using scanning electron microscopy (SEM), Brunauer – Emmett – Teller (BET) surface area analysis, and zeta potential measurements. These techniques revealed changes in surface morphology, surface area, and surface charge after chemical treatment, which contributed to enhanced adsorption behavior. Adsorption kinetics were analyzed using pseudo-first and second-order models, while equilibrium data were fitted to Langmuir and Freundlich isotherms to elucidate the adsorption mechanism and capacity. The results show that fly ash, a low-cost industrial byproduct, is an effective adsorbent for dye-contaminated wastewater, offering a sustainable solution for both pollution control and waste reuse.