Chromium-containing wastewater effectively removed by TiO2 microsphere of different sizes through a green pathway

Efficient and environmental-friendly removal of heavy metal Cr(VI) from water sources is a key challenge in current environmental management. Photocatalysis provides a feasible and ecofriendly solution for the elimination of heavy metal ions. In this study, Anatase TiO 2 microspheres (TMS) with abundant porous structure as well as excellent dispersion and uniform size were constructed through a sol-gel method after calcination by utilizing titanium sulfate as precursor. And the particle size can be regulated in the range of 0.6-4 μm by adjusting the oil-water ratio. The morphology was observed by scanning electron microscope (SEM) and the microstructure was studied by transmission electron microscope (TEM). Moreover, the specific surface area was determined to be about 200-260 m 2 /g by Brunauer-Emmett-Teller (BET) method with the N 2 adsorption-desorption test. Besides, the existence state and phase composition were studied by X-ray diffraction (XRD), Raman spectroscopy (Raman) and X-ray photo-electron spectroscopy (XPS). Then, the most likely formation mechanism is proposed, namely the temperature-induced active aggregation of nanoparticles and subsequent combination of major particles. Afterwards, the optical properties of TMS were characterized by UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). The photocatalytic degradation efficiency of Cr(VI) (100 ml, 20 mg/L) reached 99% after 100 min with 10 mg of TMS and remain stable in four cycles, which indicates that TMS is an superb choice for the removal of wastewater containing Cr(VI). In addition, the photocatalytic degradation of Cr(VI) of different scavengers and different pH values was studied. Based on the above analysis, the potential photocatalytic degradation mechanism of Cr(VI) by TMS under simulated sunlight illumination was proposed. Therefore, this study provides an efficient strategy for the synthesis of microscale spherical TiO 2 and paves a new path for its potential application fields in wastewater treatment of containing Cr(VI). Cr(VI) can be photo-degraded by TMS under simulated sunlight.