چكيده به لاتين
During the past research studies, the removal of Azo dyes was investigated using metal oxides as photocatalysts and graphene as catalyst base. The results showed that, among different metallic oxides, Bismuth Vanadate (BiVO4) have an appropriate photo-catalytic activity in removing Azo dyes. Graphene can also be used as a base catalyst for metal oxides to prevent recombination of the electrons and the holes produced by optical stimulation, and to increase the rate and efficiency of degradation. The main purpose of this research is to investigate the removal of methyl orange dye pollutant using a graphene-BiVO4 photocatalyst.
At first, by using the Hammer method, the graphene oxide was synthesized from the graphite as a precursor. A simple hydrothermal method was also used for reduction of the graphene oxide to graphene. Then Graphene-BiVO4 nanocomposite (BVG) with percentages of 5% and 95% for graphene and BiVO4, respectively, was synthesized by using simple hydrothermal single step method. The Correctness of the syntheses was confirmed by analyzing the X-ray diffraction pattern and the scanning electron microscopy images. The results showed that the increase of the oven temperature from 120°C to 160°C for the synthesis of BVG resulted in formation of higher quality nanocomposite and an increase in the rate of methyl orange degradation. Doses of 200, 600, 1000, 1400, and 1800 mg/L of BVG were tested for the degradation of 50 cc methyl orange pollutants with a concentration of 10 ppm. The dose of 1400 mg/L showed the best result of degradation in 180 minutes. In the next step, the optical degradation of methyl orange was investigated using a combination of BVG and 1 cc of hydrogen peroxide (H2O2), which produced free radicals and cosequently a significant increase in degradation rates. Then, the effect of changing the pH value was investigated, which indicated that the pH value of 3 has the best degradation rate, the results in optimum condition of pH and Photocatalyst concentration showed that the combination of BVG was able to degrade 97% of methyl orange dye in 330 minutes under visible light radiation. In comparison, it was observed that in the above condition, the degradation performance was 15% higher than grapheme oxide, and 12% higher than BiVO4. Also, the BVG compound with addition of hydrogen peroxide under visible light radiation shows 98% of methyl orange degradation in10 minutes.
Keywords: Photocatalyst, Graphene, BiVO4, Hydrogen peroxide, Optical degradation, Methyl orange
