EARP at the crossroads: Environmental assessment in Canada

Abstract

Bi2O3 nanoplates were synthesized by an ultrasound-assisted precipitation method in aqueous solution with different times of exposure to ultrasound radiation. The formation of Bi2O3 oxide with a monoclinic structure was confirmed by X-ray powder diffraction (XRD), which was also used to determine the crystallite size and lattice strain. The characterization of Bi2O3 samples was complemented with scanning electron microscopy (SEM), which revealed the morphology of the particles as irregular, ovoid and rectangular nanoplates as a function of the time of exposure to ultrasound radiation. Infrared spectroscopy (FT-IR) was used to confirm the elimination of the bismuth nitrate used in the synthesis. The specific surface area was determined by the BET method. Diffuse reflectance spectroscopy (DRS) was used to determine the band-gap energy (Eg) of the Bi2O3 samples. The photocatalytic activity of Bi2O3 samples was evaluated with respect to the degradation reactions of rhodamine B (rhB), indigo carmine (IC) and tetracycline hydrochloride (TC) in aqueous solution under Xe lamp irradiation. The highest photocatalytic activity was identified for the sample exposed to 2 h ultrasound radiation, i.e., the sample that presented the highest crystallinity, smaller particle size and a more homogeneous morphology. The mineralization degree of organic dyes and antibiotic by Bi2O3 was determined by the total organic carbon analysis (TOC), reaching percentages of 40% for rhB, 13% for IC and 72% for TC after 24 h of Xe lamp irradiation.