Immobilization of exDNA and Phosphorous Using Ca(OH)2@Iron Oxide Magnetic Composite Derived from Steelmaking Dust

Wastewater treatment plants (WWTPs) are potentially suspected of discharging extracellular DNA (exDNA) containing antibiotic-resistant genes (ARGs) into the environment. The presence of such xenobiotic pollution along with an increased concentration of phosphates, has the potential to facilitate the proliferation of antibiotic-resistant bacterial strains, thus leading to serious public health risks. Adsorption is considered a promising approach for limiting such pollution. Especially iron-based adsorbents may efficiently remove both exDNA and phosphorus from water due to the strong chemical bonding that occurs between adsorbent and adsorbate. Additionally, various ferrous waste materials, such as electric arc furnace dust (EAFD), may be valorized and applied in water purification processes. In this study, we aim to functionalize EAFD by the dissolution-recrystallization protocol using NaOH (Fr-Na material) and Ca(OH)2 (Fr-Ca material) for alkalization and then evaluate its performance in removing exDNA and phosphates from river water and wastewater. The modification process leads to the formation of a nanocrystalline ferrihydrite layer on the surface of EAFD particles, resulting in a significant six-fold increase in the specific surface area (SAA) of the adsorbent. The ability to remove phosphate from water for materials after modification was substantially increased in comparison to raw EAFD. However, at lower concentrations (0.5 mg/l), all materials exhibited similar adsorption capabilities, while at higher exDNA concentrations (1 and 3 mg/l), Fr-Ca demonstrated the highest efficiency.