Photocatalytic Decomposition of Indigo Carmine and Methylene Blue Dyes using Facilely Synthesized Lithium Borate/Copper Oxide Nanocomposite

The leakage of factories that contain methylene blue and indigo carmine dyes into water sources causes some health problems, such as skin infections, cancer, and digestive system troubles. Consequently, in this work, a lithium borate/copper oxide nanocomposite was facilely synthesized using the pechini sol gel method. After that, the synthesized nanocomposite was used for the remarkable photocatalytic decomposition of indigo carmine and methylene blue dyes. The combination of lithium borate with copper oxide prevents fast recombination of hole/electron pairs and thus increases the efficiency of photocatalytic decomposition of indigo carmine and methylene blue dyes. This is because the interfacial charge transfer efficiency and separation of photo-generated products are dramatically improved by the combination of lithium borate with copper oxide. The synthesized nanocomposite was characterized using an ultraviolet–visible spectrophotometer (UV-Vis spectrophotometer), Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), X-ray powder diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM). The average crystallite size of the synthesized nanocomposite is 18.58 nm. The synthesized nanocomposite has two optical energy gap (E g ) values of 2.67 and 5 eV due to CuO and Li 3 BO 3 phases, respectively. In addition, the FE-SEM and HR-TEM images showed that the synthesized nanocomposite consists of polyhedral, irregular, and rod-like structures with average diameters of 237.83 and 15.75 nm, respectively. The highest decomposition percentages of 100 mL of 25 mg/L of the methylene blue (at pH = 9) and indigo carmine (at pH = 3) dyes using 0.05 g of the synthesized nanocomposite are 93.03 and 89.13%, respectively.