Sodium Ligninsulfonate-assisted Synthesis of Lithium Bismuthate/bismuth Oxide Microspheres and Solar Light Photocatalytic Performance

Background: Great attention has been paid to the environmental pollution by organic dyes, which are difficult to be degraded in the natural environment and have been an unavoidable and urgent global problem. It is essential to develop green wastewater treatment technology with high removal efficiency and low-cost for protecting the surrounding and human health. Objective: The aim of the research is to synthesize lithium bismuthate/bismuth oxide microspheres with good photocatalytic performance for the removal of gentian violet (GV). Methods: Lithium bismuthate/bismuth oxide microspheres were successfully prepared by a sodium ligninsulfonate-assisted hydrothermal synthesis route. The lithium bismuthate/bismuth oxide microspheres were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform infrared spectroscopy (FTIR), and solid UV-vis diffuse reflectance spectrum. Results: XRD pattern and SEM observation show that the lithium bismuthate/bismuth oxide microspheres are composed of cubic LiBi12O18.50 and monoclinic Bi2O3 with a diameter of 250 nm-1 μm. Irregular microscale and nanoscale particles are formed under low hydrothermal temperature, low sodium ligninsulfonate concentration, and short duration time. By increasing the sodium ligninsulfonate concentration, hydrothermal temperature, and duration time, irregular particles are transferred into microspheres. Lithium bismuthate/bismuth oxide microspheres possess a band gap energy of 1.85 eV, suggesting good visible light absorption ability. The photocatalytic removal ability for GV is enhanced by prolonging light irradiation time and microspheres dosage. GV solution with the concentration of 10 mg•L-1 is able to be totally degraded by 10 mg lithium bismuthate/bismuth oxide microspheres in 10 mL GV solution under solar light irradiation for 6 h. Conclusion: The lithium bismuthate/bismuth oxide microspheres show good photocatalytic removal ability toward GV in wastewater under solar light irradiation.