Effect of alumina on photocatalytic activity of iron oxides for bisphenol A degradation

Abstract

To study the photodegradation of organic pollutants at the interface of minerals and water in natural environment, three series of alumina-coupled iron oxides (Al 2O 3–Fe 2O 3-300, Al 2O 3–Fe 2O 3-420, and Al 2O 3–Fe 2O 3-550) with different alumina fraction were prepared and characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and Barret–Joyner–Halender (BJH), and Fourier transform infrared spectra (FTIR). The XRD results showed that existence of alumina in iron oxides could hinder the formation of maghemite and hematite, and also the crystal transformation from maghemite to hematite during sintering. It has been confirmed that the BET surface area and micropore surface area of Al 2O 3–Fe 2O 3 catalysts increased with an increased dosage of alumina and with decreased sintering temperature. The pore size distribution also depended on the fraction of alumina. Furthermore, all Al 2O 3–Fe 2O 3 catalysts had a mixed pore structure of micropore, mesopore and macropore. FTIR results showed that FTIR peaks attributable to Fe–O vibrations of maghemite or hematite were also affected by alumina content and sintering temperature. It was confirmed that the crystal structure and crystalline, the surface area and pore size distribution of Al 2O 3–Fe 2O 3 catalysts depend strongly on the content of alumina and also sintering temperature. Bisphenol A (BPA) was selected as a model endocrine disruptor in aquatic environment. The effects of alumina on the photocatalytic activity of iron oxides for BPA degradation were investigated in aqueous suspension. The experimental results showed that the dependence of BPA degradation on the alumina content was attributable to the crystal structure, crystalline and also the properties of their surface structures. It was confirmed that the mixed crystal structure of maghemite and hematite could achieve the higher photocatalytic activity than maghemite or hematite alone.