Application of fly ash modified by alkaline fusion as an effective adsorbent to remove methyl violet 10B in water

Abstract

Fly ash (FA) was modified through alkaline fusion with NaOH (MFAAF) and applied as an adsorbent to remove methyl violet 10B (MV10B) in an aqueous medium. It was found that the alkaline fusion provided a significant reduction of the crystalline phase of FA. FA and MFAAF are mainly composed of aluminum, silicon, and iron oxides. The pore volume and surface area values of MFAAF were 0.1541 and 65.4 m2 g−1, being 154 and 130 times higher than the precursor material. Alkaline fusion led to an alteration in the morphology, from spheres to an undefined shape. MFAAF presented an MV10B removal percentage eight times higher than the FA, employing an adsorbent amount of 1 g L−1 at pH 7.5. The pseudo-second-order model well-described adsorption kinetics. For the equilibrium data, the Freundlich model was the proper one. At 298 K, the maximum adsorption capacity was 77.61 mg g−1. The adsorptive process was exothermic and spontaneous. MFAAF adsorbent was effective in removing 62.3% of coloration from the simulated effluent. Last, the regeneration test shows that the adsorbent can maintain the adsorption capacity during 5 cycles. These results indicate that the MAAF revealed the potential to be used as an adsorbent in industrial adsorption processes.