Fe3O4/multi-walled carbon nanotubes as an efficient catalyst for catalytic ozonation of p-hydroxybenzoic acid

Abstract

Fe 3 O 4 /multi-walled carbon nanotubes were prepared, characterized and used as a nanocatalyst for ozonation of p-hydroxybenzoic acid. The stability and reusability of the catalyst was evaluated. Characterization techniques including X-ray diffraction, Fourier transform infrared absorption spectroscopy, scanning electron microscope, high-resolution transmission electron microscopy and physical property measurement were used to analyze the reason for the decrease in catalyst activity. The addition of t-butanol and bicarbonate were used to explore the different process between hydroxyl radicals and ozone. The experimental results showed that the catalytic ozonation could significantly increase the degradation and mineralization of p-hydroxybenzoic acid. The initial pH value was a crucial factor influencing ozone decomposition and the surface property of catalyst or organic pollutant. The degradation of p-hydroxybenzoic acid increased by 32 % in catalyzed ozonation compared to single ozonation after 5 min reaction with unadjusted pH (about 5.4). In batch experiments, the removal efficiency of p-hydroxybenzoic acid and total organic carbon decreased 36.1 and 6.8 % after six run times. Bicarbonate significantly inhibited the mineralization of p-HBA, but it had almost no influence on the catalytic degradation of p-hydroxybenzoic acid. A possible pathway for p-hydroxybenzoic acid degradation was tentatively proposed.

Catalytic ozonation of sulfamethazine antibiotics using Fe3O4/multiwalled carbon nanotubes

“…Moreover, it was found that deporonation at higher pH made the SMX more reactive toward molecular ozone than neutral SMX . This result was consistent with our previous study, in which p‐HBA degradation was performed in single ozonation system . In our previous study, the similar result was also obtained for the ozonation of dimethyl phthalate .…”

“…Therefore, when initial pH was 4, SMT (pk a 5 5.8) was protonated, showing a positive charge and Fe 3 O 4 /MWCNTs acted as a cation exchanger, which accelerated the reaction rate. This pH effect was different with our previous research [38], where with the increase of pH, the degradation efficiency of p-HBA increased in the same catalytic ozonation system. The difference might be caused by the different pKa of organic pollutants, which lead to different adsorption or ion exchange effects.…”

Photocatalytic degradation of industrial pulp and paper mill effluent using synthesized magnetic Fe 2 O 3 -TiO 2 : Treatment efficiency and characterizations of reused photocatalyst

“…FTIR spectrum of Fe 2 O 3 -TiO 2 was similar to P25, which denoted that Fe 2 O 3 was well-infused into the TiO 2 lattice (Ghorai et al, 2011). Broad band at 3400 cm -1 was assigned to hydrogen bonded OH whereas band at 1634 cm -1 corresponded to the adsorbed water (Bai et al, 2016). These two bands played a significant role in photocatalytic reactions to react with photogenerated holes on Fe 2 O 3 -TiO 2 surface upon irradiation.…”

“…Despite that, the reused photocatalyst exhibited excellent chemical stability from the first to fifth cycles without significant decrease in photoactivity (76.9-75.6% of COD removal). Minor decline observed was due to poisoning of Fe 2 O 3 -TiO 2 active sites by adsorbed intermediates and pollutants, incomplete recovery of Fe 2 O 3 -TiO 2 , and possible separated phase of magnetic catalyst (Bai et al, 2016;Pang et al, 2016). Nonetheless, a minimal decrease in photocatalytic efficiency from the fresh to fifth-cycle of Fe 2 O 3 -TiO 2 (80.6-75.6% of COD removal) strongly supported that the mechanochemically synthesized Fe 2 O 3 -TiO 2 was stable and resistant towards photo-corrosion during photocatalytic reaction (Qin et al, 2014).…”

Degradation of sulfamethazine antibiotics in Fenton‐like system using Fe3O4 magnetic nanoparticles as catalyst

“…Recently, studies have been carried out to improve the mineralization by synthesizing Fe 3 O 4 composites that include activated carbon, graphene oxide , multiwalled carbon nanotubes , and some kinds of materials. Several pollutants degraded by a Fenton‐like system using Fe 3 O 4 MNPs alone and Fe 3 O 4 composites are summarized in Table .…”