Fly ash-based zeolitic materials of different surface chemistry and texture: Insight into adsorption performance and mechanisms of aqueous BTEX removal

Abstract

Water contamination caused by anthropogenic, and unforecasted release of BTEX (benzene, toluene, ethylbenzene and xylene) compounds threatens the quality and integrity of aquatic ecosystems. BTEX sorption with novel materials characterized by increased hydrophobicity and stability has been proposed to overcome such contamination. This study aimed to investigate the whole array of hydrothermally synthesized zeolitic materials exhibiting different properties, as well as zeolite/carbon and zeolite/vermiculite composites, to analyse their potential in removing aqueous BTEX. Various parameters and experimental conditions, including the type of volatile organic compounds (VOCs), initial concentration, BTEX coexistence, and increased solution salinity, were studied to verify the applicability of the derived materials. The adsorption capacity of the materials and their governing removal mechanisms were additionally elucidated. The primary removal mechanism involved partitioning on unburned carbon residues, which was observed in zeolite/carbon composites showing the highest BTEX removal efficiency. NaA-zeolite/carbon composite was the most effective in removal of BTEX, with the removal capacity of 15.36 mg/g towards p-xylene. Moreover, the increased salinity of the BTEX solution affects adsorption performance for polar adsorbates, irrespectively of the applied zeolite/carbon composite. Fly-ash (FA) and high-carbon fly-ash (HCFA) were successfully valorised into products with better textural features. These products may effectively tackle organic water pollution caused by VOCs under near-real-life conditions.