Photocatalytic Degradation of 4,4′-Isopropylidenebis(2,6-dibromophenol) on Magnetite Catalysts vs. Ozonolysis Method: Process Efficiency and Toxicity Assessment of Disinfection By-Products

Abstract

Flame retardants have attracted growing environmental concern. Recently, an increasing number of studies have been conducted worldwide to investigate flame-retardant sources, environmental distribution, living organisms’ exposure, and toxicity. The presented studies include the degradation of 4,4′-isopropylidenebis(2,6-dibromophenol) (TBBPA) by ozonolysis and photocatalysis. In the photocatalytic process, nano- and micro-magnetite (n-Fe3O4 and μ-Fe3O4) are used as a catalyst. Monitoring of TBBPA decay in the photocatalysis and ozonolysis showed photocatalysis to be more effective. Significant removal of TBBPA was achieved within 10 min in photocatalysis (ca. 90%), while for ozonation, a comparable effect was observed within 70 min. To determine the best method of TBBPA degradation concentration on COD and TOC, the removals were examined. The highest oxidation state was obtained for photocatalysis on μ-Fe3O4, whereas for n-Fe3O4 and ozonolysis, the COD/TOC ratio was lower. Acute toxicity results show noticeable differences in the toxicity of TBBPA and its degradation products to Artemia franciscana and Thamnocephalus platyurus. The EC50 values indicate that TBBPA degradation products were toxic to harmful, whereas the TBPPA and post-reaction mixtures were toxic to the invertebrate species tested. The best efficiency in the removal and degradation of TBBPA was in the photocatalysis process on μ-Fe3O4 (reaction system 1). The examined crustaceans can be used as a sensitive test for acute toxicity evaluation.

Non-stoichiometric magnetite as catalyst for the photocatalytic degradation of phenol and 2,6-dibromo-4-methylphenol – a new approach in water treatment

“…The selected catalysts were characterized by SEM, X-ray diffraction, and ultraviolet–visible (UV–vis) analysis. The XRD and UV–vis results were published in our previous article [ 17 ]. We present this data again in this article as it is necessary for the discussion of the results.…”

“… X-ray diffraction measurements of M1 (red), M2 (blue) (a), and UV–vis absorption spectra of M1 (red) and M2 (blue) (b). Figure 1a and 1b were adapted from [ 17 ] (© 2022 J. Kisała et al, distributed under the terms of the Creative Commons Attribution 4.0 International License, https://creativecommons.org/licenses/by/4.0). …”

“…Electron hopping along the octahedral iron chain handles its conductivity and redox properties, causing the magnetite to initialize oxidation/reduction reactions. Fe 3 O 4 nanoparticles have been used as a photocatalyst for the degradation of azo dyes [ 15 ], for wastewater treatment [ 16 – 17 ], for water decomposition, and for Cr(VI) reduction [ 18 ].…”

“…Two types of magnetite (M1 and M2) were used as catalysts in the photocatalysis process. The same type of magnetite catalysts has been investigated by us in our previous article [ 17 ] as photocatalysts for the degradation of 4,4′-isopropylidenebis(2,6-dibromophenol) in comparison with ozonolysis. Magnetite was chosen as a photocatalyst because of its low cost, interesting electron properties, and indisputably low environmental impact.…”