The Effect of Milling Time on Band Gap Value in Thin Layers of Nano Photocatalyst MnO₂/CuO/Fe₂O₃

Abstract Waste from laundry washing discharged into waterways without pre-treatment can cause problems that hurt water quality because they contain oxidizing agents such as bleach for clothes. This study aims to determine the effect of milling time variations on the value of the band gap in thin film MnO 2 /CuO/Fe 2 O 3 and their photocatalytic activity capabilities. This study’s milling time variations were 5 hours, 10 hours, and 15 hours. They were grinding MnO 2 /CuO/Fe 2 O 3 materials using a High Energy Milling (HEM-E3D) tool to obtain the nano size of these particles. Synthesis of MnO 2 /CuO/Fe 2 O 3 nanocomposites using the sol-gel method and the spin coating method to manufacture thin films using a glass substrate to be sampled in testing photocatalyst activity. Characterization testing uses a spectroscopy (Uv-Vis) tool to obtain a band gap value. The band gap values were 5 hours milling at 1.87 eV, 10 hours milling at 1.72 eV, and 15 hours milling at 1.64 eV. Here it shows that the longer the milling time, the smaller the band gap energy obtained. Shrinking the energy gap will experience a good photocatalyst process. The results of this study show the effect of the catalyst in degrading pollutants with the best degradability of 50.67%.