Upcycled materials for water treatment and emerging contaminant recovery: a preliminary study on waste-derived magnetic zeolites

Abstract

This study explores the applicability of magnetic zeolites from industrial waste—specifically fly ash (FA) combined with either synthetic Fe-based nanoparticles (FANPs1 and FANPs2) or red mud (RM) in differing ratios (FA1RM1 and FA4RM1)—for the removal and recovery of emerging water contaminants. FA and RM originate from coal combustion in thermoelectric power plants and alumina extraction from bauxite, respectively. The resulting materials were first assessed for acute toxicity on a freshwater model organism, revealing no acute effects. They were then tested under environmentally relevant conditions for the removal of ofloxacin (OFL), a fluoroquinolone antibiotic selected as a representative water-persistent contaminant. Subsequently, three extraction techniques—ultrasound-assisted extraction (UsAE), microwave-assisted extraction (MwAE), and magnetic hyperthermia-assisted extraction (MhAE)—were applied to recover the adsorbed OFL. All materials exhibited high OFL loading efficiencies (80–95%). Among the extraction techniques, MwAE yielded the highest OFL recovery (>80% for FANPs2 and FA4RM1), while UsAE and MhAE achieved lower efficiencies (up to ∼60%), regardless of the adsorbent used. Post-loading and post-extraction characterization studies provided insights into the adsorption mechanism and revealed significant OFL resorption across all zeolite types. Preliminary tests also confirmed the ability of these materials to capture endocrine-disrupting compounds (EDCs), underscoring their potential for water remediation and recovery applications.