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

Abstract

Phenol and 2,6-dibromo-4-methylphenol (DBMP) were removed from aqueous solutions by ozonolysis and photocatalysis. The properties and structural features of the catalysts and the organic compounds are discussed, as well as their influence on the degradation reaction rates. The degradation efficiency in photocatalytic processes was higher for DBMP (98%) than for phenol (approximately 50%). This proves the high efficiency of magnetite in the photocatalytic degradation of halogenated aromatic pollutants. The particularly high degradation efficiency regarding halogen-containing DBMP molecules and the yield of bromide ions indicate that DBMP degradation follows a mixed reduction–oxidation mechanism. DBMP molecules interact with the magnetite surface, enabling them to react with the available electrons, and, as a result, bromide ions can be released. The results confirm that magnetite is an effective photocatalyst in the degradation of halogenated aromatic pollutants.

Reductive Photodegradation of 4,4′-Isopropylidenebis(2,6-dibromophenol) on Fe3O4 Surface

“…The average crystallite sizes of F1 and F2 catalyst are 46 and 28 nm, respectively. The lengths of the edges of the magnetite unit cells measured for F1 and F2 were 8.3845 Å and 8.3595 Å, respectively [ 30 ].…”

“…Using these data and the unit cell edge length values obtained from XRD measurements of the materials F1 and F2 (8.3845 and 8.3595 Å, respectively) the x values were determined. The studied catalysts were non-stoichiometric magnetites with the x-value equal to 0.4094 and 0.1828 for F1 and F2, respectively [ 30 ]. Therefore, F1 exhibits the properties of a conductor (E bg = 0.11 eV, Figure S1 ), while F2 is a semiconductor (E bg = 1.75 eV).…”

“…All experiments were performed at pH = 10. At this pH the high stability of magnetic powders and also the good solubility of TBBPA is expected [ 30 ]. It is also worth mentioning that alkaline conditions are suitable for reduction processes [ 36 ].…”

“…The possible degradation pathway in the oxidative process consists of an initial reductive debromination and further oxidation leading to low molecular products. The slightly lower efficiency of the reduction process on the F2 (k app values were 0.1358 and 0.0916 min −1 for F1 and F2, respectively) catalyst may be due to the higher degree of oxidation of this material [ 30 ], and thus a smaller amount of Fe 2+ ions at the B sites and the limitation of electron hopping between Fe 3+ and Fe 2+ ions at the B sites. The opposite tendency (k app values for F1 and F2 were 0.3434 and 0.6713 min −1 , respectively) observed in the case of the oxidation process is probably caused by the morphology of the F2 catalyst.…”

O3 decomposition to O2 on surfaces of Silicon nanocage and Carbon nanocage as effective catalysts

“…Researchers con rmed that the e ciency and performance of photocatalytic decomposition model is strongly depended to UV-light strength and so it is made the low performance for O 3 molecules removing in normal temperature [15,16]. Researchers indicated that the catalytic decomposition model has high performance, stability and durability and this model can be considered as effective method for O 3 molecules removing in engineering application [17,18].…”