Degradation of Rhodamine B using Cu-Doped SrFeO3 thermocatalysts

Pedersen, Andreas Kruse

4. term

Chemistry, Master (Scient)

2024

2024-06-03

51

Perovskit-oxider er materialer med en bestemt krystalstruktur, som kan fungere som katalysatorer. Vi fremstillede strontiumferrat (SrFeO3) ved solution combustion synthesis og tilsatte små mængder kobber (0–10 %) på B-sitet (hvor noget af jernet erstattes). Formålet var at undersøge, hvordan kobber-doping påvirker dannelsen af Fe4+-ioner og dermed den termiske katalytiske nedbrydning af farvestoffet rhodamin B under mørke, normale omgivelser (uden lys). Røntgen-fotoelektronspektroskopi (XPS) viste, at højere kobberindhold øgede andelen af Fe4+ og mængden af ilt i krystalgitteret i forhold til overfladen. Ultraviolet–synlig (UV–Vis) spektroskopi viste fuldstændig nedbrydning af rhodamin B, når perovskitten ikke blev genbrugt. Den tilsyneladende aktiveringsenergi faldt og havde et minimum ved 5 % kobber. Ved genbrug skiftede absorptionsspektret mod kortere bølgelængder (et hypsochromisk skift). Dette tilskrives N-deethylering af rhodamin B til rhodamin 110, hvilket gjorde opløsningen grøn. For hver genbrugscyklus faldt nedbrydningshastigheden, sandsynligvis fordi metaller udludedes fra materialet til opløsningen. Atomabsorptionsspektroskopi (AAS), en metode til at måle opløste metaller, bekræftede omfattende udludning af alle metaller under den termiske katalyse, hvilket indikerer lav stabilitet. Samlet set kan SrFeO3 effektivt nedbryde rhodamin B, men omfattende udludning svækker hurtigt perovskitten og begrænser dens ydeevne ved genbrug. Fremtidigt arbejde bør sigte mod at minimere udludning, f.eks. ved at undersøge andre dopanter, og teste andre organiske forurenende stoffer for at se, hvordan perovskitten ændrer sig ved genbrug.

Perovskite oxides are materials with a specific crystal structure that can act as catalysts. We synthesized strontium ferrate (SrFeO3) by solution combustion synthesis and added small amounts of copper (0–10%) at the B-site (replacing part of the iron). Our goal was to see how copper doping affects the formation of Fe4+ ions and, in turn, the thermal catalytic breakdown of the dye rhodamine B under dark, ambient conditions (no light). X-ray photoelectron spectroscopy (XPS) showed that higher copper contents increased the fraction of Fe4+ and the amount of oxygen in the crystal lattice relative to the surface. Ultraviolet–visible (UV–Vis) measurements showed complete degradation of rhodamine B when the perovskite was not recycled. The apparent activation energy decreased and reached a minimum at 5% copper. When the perovskite was reused, the absorption spectrum shifted to shorter wavelengths (a hypsochromic shift). We attribute this to N-deethylation of rhodamine B to rhodamine 110, which turned the solution green. With each recycling cycle, the degradation rate dropped, likely because metals leached from the material into the solution. Atomic absorption spectroscopy (AAS), a technique for measuring dissolved metals, confirmed extensive leaching of all metals during thermal catalysis, indicating low catalyst stability. Overall, SrFeO3 can effectively degrade rhodamine B, but extensive leaching quickly weakens the perovskite and limits its performance upon reuse. Future work should aim to minimize leaching, for example by exploring other dopants, and test other organic pollutants to see how the perovskite changes with recycling.

[This summary has been rewritten with the help of AI based on the project's original abstract]

Perovskit ; Thermokatalyse ; Strontium Ferrate ; XPS ; XRD ; AAS ; Recycling ; Organic pollutant ; Rhodamine B

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