Reusable and inductively regenerable magnetic activated carbon for removal of organic micropollutants from secondary wastewater effluents

Asya Drenkova-Tuhtan; Caleb Stewart Inskeep; Leoni Luthardt; Sara Li Deuso; Thomas Ballweg; Doris Hanselmann; Zoé Béalu; Carsten Meyer; Benedikt Schug; Heidrun Steinmetz; Karl Mandel

doi:10.1016/j.watres.2024.121525

Reusable and inductively regenerable magnetic activated carbon for removal of organic micropollutants from secondary wastewater effluents

Water Res. 2024 May 15:255:121525. doi: 10.1016/j.watres.2024.121525. Epub 2024 Mar 26.

Authors

Affiliations

¹ University of Stuttgart, Institute for Sanitary Engineering, Water Quality and Solid Waste Management (ISWA), Bandtaele 2, Stuttgart 70569, Germany; National Institute of Chemical Physics and Biophysics, Laboratory of Environmental Toxicology, Akadeemia tee 23, Tallinn 12618, Estonia. Electronic address: asya.drenkova@kbfi.ee.
² University of Stuttgart, Institute for Sanitary Engineering, Water Quality and Solid Waste Management (ISWA), Bandtaele 2, Stuttgart 70569, Germany.
³ Friedrich-Alexander University Erlangen-Nürnberg (FAU), Egerlandstraße 1, Erlangen 91058, Germany.
⁴ Fraunhofer Institute for Silicate Research ISC, Neunerplatz 2, Würzburg 97082, Germany.
⁵ University of Kaiserslautern-Landau (RPTU), Department of Civil Engineering - Resource Efficient Wastewater Technologies, Paul-Ehrlich 14, Kaiserslautern 67663, Germany.
⁶ University of Kaiserslautern-Landau (RPTU), Department of Civil Engineering - Resource Efficient Wastewater Technologies, Paul-Ehrlich 14, Kaiserslautern 67663, Germany. Electronic address: heidrun.steinmetz@rptu.de.
⁷ Friedrich-Alexander University Erlangen-Nürnberg (FAU), Egerlandstraße 1, Erlangen 91058, Germany; Fraunhofer Institute for Silicate Research ISC, Neunerplatz 2, Würzburg 97082, Germany. Electronic address: karl.mandel@fau.de.

PMID: 38569358
DOI: 10.1016/j.watres.2024.121525

Abstract

This work introduces a new sustainable alternative of powdered activated carbon (PAC) - magnetically harvestable and reusable after regeneration via inductive heating - for the adsorptive removal of organic micropollutants (OMP) from secondary wastewater effluents. For this purpose, two commercial PACs - lignite "L" (1187 m²/g) and coconut "C"-based (1524 m²/g) - were modified with magnetic iron oxide following two different synthesis approaches: infiltration ("infiltr") and surface deposition ("depos") route. The resulting magnetic powdered activated carbons (mPAC) and their precursor PACs were fully characterized before application. The iron oxide content of the modified "L" and "C" samples was ∼30 % and ∼20 %, respectively. Iron oxide gives the PAC beneficial magnetic properties for easy magnetic separation and simultaneously acts as an inductively heatable agent for the carbon regeneration. The infiltrated samples displayed better inductive heating performance and regeneration than their deposited counterparts. Tests with real wastewater showed fast adsorption kinetics of the organic load following the pseudo-second-order kinetic model. Adsorption isotherms were compliant with the Freundlich isotherm model. Sample "L-infiltr" had the best overall adsorption performance throughout 5 reuse cycles when intermediately inductively regenerated (<3 % drop in organics removal per cycle with intermediate regeneration vs. ∼10 % drop per cycle without regeneration). The treated supernatant was additionally tested for 31 representative organic micropollutants and their transformation products (pharmaceuticals, personal care products, industrial chemicals, etc.), where 26 OMPs had consistently high removal (>85 %) throughout 5 cycles with intermediate regeneration and for 28 OMPs the total adsorption efficiency dropped by <5 % after 5 cycles.

Keywords: Magnetic induction; Magnetite; Organic micropollutants; Reusable powdered activated carbon; Reversible sorption; Wastewater effluents.