STUDY ON THE UTILIZATION OF TIO₂/NISE/N/C FOR CR(VI) PHOTOREDUCTION

The toxic contaminant chromium is commonly found in industries such as electroplating, metallurgy, and metal processing. Cr(VI) ions are highly toxic, carcinogenic, and mutagenic. Photocatalytic reduction has emerged as a promising method for Cr(VI) removals due to its high efficiency, cost-effectiveness, and the absence of secondary pollutants. TiO2 was chosen as a photocatalyst due to its exceptional photocatalytic activity. However, TiO2 has the disadvantage of a broad bandgap and rapid electron-hole recombination. To overcome this drawback, a heterojunction is formed between TiO2 and NiSe. Nevertheless, TiO2/NiSe suffers from poor thermal stability and a tendency to agglomerate. To address these issues, NiSe is modified using carbon and nitrogen materials derived from chitosan. In this research, TiO2/NiSe modified with N/C has been synthesized through the solvothermal method as a photocatalyst utilizing two forms of TiO2, namely rutile (Rk) and P25 (Pk). The resulting photocatalysts are optimized for reducing Cr(VI) in water through photocatalysis. X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), UV-Diffuse Reflectance Spectroscopy (UV-DRS), and Fourier Transform Infrared (FTIR) spectroscopy were utilized for characterization. The UV-Vis DRS analysis indicated a reduction in the bandgap upon incorporating carbon and nitrogen elements. Rutile TiO2's bandgap has decreased from 3 eV to 2.87 eV, while P25 TiO2’s bandgap has decreased from 3.14 eV to 3.04 eV. The photoreduction study of TiO2/NiSe/N/C in water against Cr(VI) was also conducted with several variations, namely light source (no light, TL lamp, 365 nm lamp, 254 nm lamp) and hole scavenger (formic acid). The photoreduction test results demonstrate the superior performance of the composite compared to pure TiO2. For example, under 254 nm light, the P25 sample significantly improved from 20.41% (P) to 53.26% (Pk). The Rk sample shows the strongest activity in TL light, which achieved a photoreduction rate of up to 48%. The best photoreduction study results were obtained by the Pk sample at 254 nm lamp variation using a formic acid hole scavenger with 99.7% photoreduction.