Catalytic applications of mesoporous CaBi2O4 obtained from a single source precursor

摘要

With the aim of generating mesoporous CaBi2O4 and further to investigate its catalytic properties, thermolysis of mineral beyerite was carried out between 650 and 800 degrees C for varying durations. Monophasic CaBi2O4 emerged after calcination of beyerite at 675 degrees C for 24h. Successful Rietveld refinement of powder X-ray diffraction pattern of this sample was achieved in C2/c space group with a=16.6066 (9) angstrom, b=11.5884 (6) angstrom and c=13.9915 (8) angstrom, =134.029 degrees. Dumbbell-shaped morphology of crystallites was observed in field emission scanning electron microscopic images. The energy dispersive spectral analysis at various locations of the sample confirmed the atomic ratio of Ca, Bi and O close to 1:2:4. Presence of fingerprint modes in the Raman spectrum of this sample augmented the results from powder X-ray diffraction. Absorption over the entire ultraviolet region and part of the visible region along with tailing was noticed in the UV-visible spectrum of this sample. The direct band gap energy was found to be 2.67eV. From nitrogen adsorption-desorption isotherms, surface area of 78m(2)g(-1) and pore diameter of 5.18nm were deduced. Reduction of harmful 4-nitrophenol and carcinogenic Cr(VI) was catalyzed efficiently by this sample. Kinetics of reduction of 4-nitrophenol has also been examined. Recyclability experiments were successful up to four cycles. Possible mechanisms operative in these sets of reactions have been discussed.