Industrial waste against pollution: mill scale-based magnetic hydrogels for rapid abatement of Cr(vi)

Year: 2024

Authors: Boontanom A., Maddaloni M., Suwanpinij P., Vassalini I., Alessandri I.

Autors Affiliation: King Mongkuts Univ Technol North Bangkok, Sirindhorn Int Thai German Grad Sch Engn TGGS, Bangkok 10800, Thailand; UdR Brescia, INSTM, Brescia, Italy; Univ Brescia, Mech & Ind Engn Dept DIMI, Chem Technol Lab, Via Branze 38, I-25123 Brescia, Italy; Univ Brescia, Dept Informat Engn DII, Via Branze 38, I-25123 Brescia, Italy; INO CNR, Via Branze 38, I-2513 Brescia, Italy; Leibniz Inst Werkstofforientierte Technol IWT, Met & Met Forming, Badgasteiner Str 3, D-28359 Bremen, Germany.

Abstract: This work studies the adsorption of hexavalent chromium from water using magnetic composite hydrogels obtained by combining magnetite micropowders, synthesized from industrial by-products, with a natural biopolymer (alginate) and other active species that could be obtained from food waste, like ascorbic acid. In particular, mill scale was collected from a steel hot strip mill, converted into magnetite microparticles and encapsulated in alginate-based hydrogel bubbles, in combination with activated carbon (AC) and L-ascorbic acid (VitC). The synergistic combination of each active component creates an efficient, multifunctional hybrid adsorbing unit, which enables the total abatement of Cr(VI) from contaminated water, even at a high concentration range (up to 50 mg L-1). Alginate plays the double role of water-absorbing and Cr(VI)-adsorbing matrix as well as that of carrier and container for the other active components, among which AC is utilized as an extra-adsorbing unit for Cr(VI), while VitC enables reduction of Cr(VI). Furthermore, the presence of Fe3O4 microparticles endows the hydrogel bubbles with magnetic responsiveness, enabling their easy removal at the end of their decontaminant activity by means of small magnets. The adsorption capability of the Fe3O4/AC/VitC-alginate hydrogels was tested under different conditions: Cr6+ was completely abated within 60 minutes when the Cr(VI) concentration in ultrapure water was equal to 20 mg L-1, and within 360 minutes when the concentration in ultrapure water was 50 mg L-1, without need of any pH-regulating treatment. The role of each different active unit was investigated and compared to the adsorption performances of whole composite systems, elucidating cooperative effects and deriving optimized formulations. The composite hydrogels were also tested in real contaminated water in the presence of other possible common competitive inorganic species and in non-acidic pH. Under these conditions it was also possible to obtain complete Cr(VI) removal, even if with slower kinetics, and 93% Cr(VI) (50 mg L-1) was abated within 60 minutes.

Journal/Review: ENVIRONMENTAL SCIENCE-WATER RESEARCH & TECHNOLOGY

Volume: 10 (2)      Pages from: 551  to: 564

More Information: The research is funded by a Research and Researchers for Industries scholarship under Thailand Research Fund (Contract number PHD60I0081). I. V. is partially supported by the Italian Ministry of University and Research (MUR) through the PRIN project NOMEN (2017MP7F8F).
KeyWords: Hexavalent Chromium; Aqueous-solutions; Water Treatment; Ascorbic-acid; Iron-oxides; Removal; Reduction; Nanoparticles; Beads; Ions
DOI: 10.1039/d3ew00490b

Citations: 1
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