Preparing a Ca-Bi-O System by the Precipitation Method and Studying Its Intermediate Structural Properties for Applications in Water Treatment

This study focuses on the development of a Ca-Bi-O system (CBO) with efficiency in the degradation of Rhodamine B, which is extremely toxic to many organisms and can have long-term negative consequences if not safely removed from the water. The conventional precipitation method was used to create a stable phase of Ca2Bi2O5 with a stoichiometric 1:1 molar ratio of Ca:Bi. Before obtaining the pure phase, the details of the reaction processes were investigated and the various intermediate products were identified using X-ray diffraction followed by Fourier transform infrared, UV-Vis, and Raman spectroscopy. An ab initio calculation evaluated with the HSE06 functional yields a band gap of 3.5 eV, similar to the band gap obtained by diffuse reflectance recorded on Ca2Bi2O5. This newly synthesized compound is addressed to the environmental application by investigating the photocatalytic properties of CBO materials obtained at different calcination temperatures. The investigation of pure Ca2Bi2O5, with characterization techniques and complemented by new first-principles calculations to investigate the photocatalysis provide valuable new insights for this scarcely studied yet potentially interesting compound.