Pewarna sintesis merupakan salah satu bahan pencemar lingkungan perairan karena sifatnya yang sulit terurai dan persisten sehingga dapat menghambat penetrasi cahaya matahari masuk ke dalam air dan menyebabkan penurunan aktivitas fotosintesis. Fotokatalitik dilakukan untuk mendegradasi pewarna sintesis dengan menggunakan CuBi2O4 yang memiliki energi celah pita sebesar 1.75 eV. Namun, rekombinasi pasangan e-/h+ pada CuBi2O4 dapat terjadi akibat celah pita yang sempit serta karena memiliki sifat mobilitas pembawa muatan yang buruk. Untuk mengurangi rekombinasi pasangan e-/h+ pada CuBi2O4 ditambahkan Ag sehingga efisiensi degradasi fotokatalitik meningkat. CuBi2O4 disintesis melalui metode solvotermal sedangkan Ag/CuBi2O4 disintesis melalui metode presipitasi-reduksi dengan rasio mol prekursor Ag:CuBi2O4 (1:1), (2:1), dan (1:2). Hasil sintesis CuBi2O4 dan nanokomposit Ag/CuBi2O4 dikarakterisasi dengan XRD, TEM, FTIR, dan Spektroskopi UV-Vis DRS. Kemampuan fotokatalitik Ag/CuBi2O4 untuk mendegradasi metilen biru dianalisis dengan variasi jenis katalis, variasi massa katalis (5 mg, 10 mg, dan 15 mg), variasi waktu iradiasi, dan variasi kondisi (adsorpsi dan fotolisis). Hasil degradasi metilen biru oleh CuBi2O4 dan Ag/CuBi2O4 dianalisis dengan Spektroskopi UV-Vis. Hasil penelitian menunjukkan bahwa penambahan Ag pada CuBi2O4 meningkatkan aktivitas fotokatalitik. Persentase degradasi metilen biru yang terbesar terjadi pada 10 mg Ag/CuBi2O4 (2:1) yaitu sebesar 82,51% dengan konstanta laju sebesar 9,07 x 10-3 menit-1.

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Synthetic dyes are one of the pollutants in the aquatic environment because they are difficult to decompose and are persistent, so they can inhibit the penetration of sunlight into the water and cause a decrease in photosynthetic activity. Photocatalytic was performed to degrade synthetic dyes using CuBi2O4 which has a band gap energy of 1.75 eV. However, recombination of the e-/h+ pair on CuBi2O4 can occur due to the narrow band gap and because it has poor charge carrier mobility. In order to reduce the recombination of e-/h+ pairs in CuBi2O4, Ag was added so that the efficiency of photocatalytic degradation increased. CuBi2O4 was synthesized by the solvothermal method while Ag/CuBi2O4 was synthesized by the precipitation-reduction method with the mole ratio of Ag:CuBi2O4 precursors (1:1), (2:1), and (1:2). The CuBi2O4 and Ag/CuBi2O4 nanocomposites produced were characterized by XRD, TEM, FTIR, and UV-Vis DRS. The photocatalytic ability of Ag/CuBi2O4 nanocomposites in degrading methylene blue was analyzed with various catalyst types, catalyst mass variations (5 mg, 10 mg, and 15 mg), irradiation time variations, and conditions variations (adsorption and photolysis). Degradation results of methylene blue by CuBi2O4 and Ag/CuBi2O4 were analyzed by UV-Vis spectroscopy. The results showed that the addition of Ag into CuBi2O4 increased the photocatalytic activity. The greatest percentage of methylene blue degradation occurred at 10 mg Ag/CuBi2O4 (2:1) which was 82,51% with a rate constant of 9.07 x 10-3 min-1.