Preparation of Bi2O3 Nanostructures and Their Light Driven Catalytic Activity Towards the Erasure of Textile Dyes

Christina, Previtha John Devasahayam (2016) Preparation of Bi2O3 Nanostructures and Their Light Driven Catalytic Activity Towards the Erasure of Textile Dyes. Final Year Project, UTAR.

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Abstract

Azo dyes are widely used in the textile industry and as they exhibit undesirable aftereffect such as eutrophication, considerable amounts of research were dedicated towards its removal. Wide spectrums of technologies were devised and amongst them, heterogeneous photocatalysis incorporating bismuth trioxide (Bi2O3) surfaces as a potential means for wastewater treatment. Bi2O3 nanoflakes were synthesized via a co-precipitation method using cetyltrimethyl ammonium bromide (CTAB) as a surfactant. XRD, FESEM-EDX and UV-Vis DRS analyses were conducted to determine the crystal phase, morphology and band gap energy of the photocatalyst. The synthesised Bi2O3 was identified to be in the α-monoclinic phase and a determined band gap of 2.95 eV. The nanostructure was observed to be a flake-like Bi2O3 and had an average length of 250 nm and 60 nm thickness. The possible growth mechanism of Bi2O3 nanoflakes was also proposed. The photocatalytic activity of Bi2O3 nanoflakes were tested in the degradation of methyl green (MG) under fluorescent light irradiation. Comparison studies were conducted on commercial Bi2O3 and TiO2 and were found that the Bi2O3 nanoflakes exhibited superior degradation of MG. Sedimentation test was conducted on the nanoflakes and commercial TiO2 and was found that the nanoflakes settled well after 30 minutes as compared to TiO2. The optimal operational parameters were determined to be 10 mM H2O2, 5 mg/L MG and pH 7. 100% of MG degradation was achieved within 20 minutes of irradiation while 81% of chemical oxygen demand (COD) was removed after 80 minutes of irradiation. Other dyes such as methylene blue (MB) and rhodamine B (RhB) could also be degraded by Bi2O3 under similar experimental conditions with their degradation efficiency in descending order MG > MB > RhB.

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