Salah satu limbah pewarna dari industri tekstil adalah metilen biru. Metilen biru (MB) banyak digunakan karena warnanya yang cerah dan stabil. Namun, MB bersifat beracun, tidak dapat terurai secara hayati, serta menimbulkan risiko lingkungan dan kesehatan. Untuk mengatasi masalah tersebut digunakan teknologi fotokatalis yang dapat mendegradasi senyawa organik. Pada penelitian ini, digunakan katalis WO3/g-C3N4 dengan variasi komposisi WO3 yang dikompositkan ke g-C3N4 dan variasi loading katalis. Fotokatalis di karakterisasi dengan menggunakan X-Ray Diffraction (XRD), UV-Vis Diffuse Reflectance Spectroscopy (DRS), Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX) dan Photoluminescense. Pengujian degradasi dilakukan dengan mengukur perubahan konsentrasi metilen biru sebelum dan sesudah radiasi yang diukur dengan metode Spektrofotometri UV-Vis. Hasil karakterisasi SEM/EDX menunjukkan bahwa morfologi g-C3N4 berupa lembaran, WO3 berbentuk agregat dan komposit WO3/g-C3N4 berbentuk lembaran yang tertutup agregat. Karakterisasi XRD menunjukkan Fasa kristal g-C3N4 berbentuk heksagonal, sedangkan fasa kristal WO3 didominasi oleh monoklinik. Karakterisasi UV-Vis DRS menunjukkan nilai energi band gap setiap katalis dalam rentang 2,64 - 2,86 eV, yang memungkinkan absorbansi sinar tampak. Karakterisasi photoluminescense menunjukkan Fotokatalis WO3/g-C3N4 dengan rasio 1:3 yang disintesis memiliki laju rekombinasi yang lebih rendah dibandingkan dengan g-C3N4, dengan dugaan mekanisme transfer muatan berupa Z-scheme heterojunction berdasarkan karakterisasi photoluminescence. Komposit WO3/g-C3N4 dengan rasio 1:3 merupakan komposisi yang optimal dalam mendegradasi metilen biru. Konsentrasi loading komposit WO3/g-C3N4 (1:3) optimum adalah 150 mg/L untuk larutan metilen biru 10 ppm.

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One of the dye wastes from the textile industry is methylene blue. Methylene blue (MB) is widely used because of its bright and stable color. However, MB is toxic, non-biodegradable, and poses environmental and health risks. To address these issues, photocatalytic technology is employed to degrade organic compounds. In this study, a WO3/g-C3N4 catalyst was used, with variations in WO3 composition composite to g-C3N4 and catalyst loading. The photocatalyst was characterized using X-Ray Diffraction (XRD), UV-Vis Diffuse Reflectance Spectroscopy (DRS), Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX), and Photoluminescence. Degradation testing was conducted by measuring changes in methylene blue concentration before and after radiation, using UV-Vis Spectrophotometry. SEM/EDX characterization results showed that the morphology of g-C3N4 was sheet-like, WO3 was aggregate-shaped, and the WO3/g-C3N4 composite was sheet-like covered by aggregates. XRD characterization indicated that the crystalline phase of g-C3N4 was hexagonal, while the crystalline phase of WO3 was dominated by monoclinic. UV-Vis DRS characterization showed that the band gap energy values of each catalyst ranged from 2.64 to 2.86 eV, enabling visible light absorption. Photoluminescence characterization shows that the WO3/g-C3N4 photocatalyst synthesized with a 1:3 ratio has a lower recombination rate compared to g-C₃N₄, with the proposed charge transfer mechanism being a Z-scheme heterojunction based on photoluminescence characterization. The WO3/g-C3N4 composite with a 1:3 ratio is the optimal composition for degrading methylene blue. The optimal loading concentration of the WO₃/g-C₃N₄ composite (1:3) is 150 mg/L for a 10 ppm methylene blue solution.