Study On The Properties Of Boron-doped Iron Oxides And Their Photocatalytic Effect On The Degradation Of Organic Pollutants

Organic pollutant oxidation and degradation using iron oxides as catalysts has been studied in recent years. The band energy of iron oxides is lower than TiO2 and iron oxides can easily induce Fenton reaction, compared with TiO2, a traditional photocatalytic material. Therefore, iron oxides catalyzing is considered to be a new method of treating environmental pollution.Different B-doped goethite and hematite were prepared using trimethyl borate in order to improve their structure and photocatalytic activity. Sol-gel method and calcination method with grinding were used to prepare B-doped iron oxides, and XRD, FT-IR, DRS and BET were used to explain the structure and photocatalytic activity. Different parameters such as composite method, the ratio of B-doping, pH, H2O2 and light were discussed to estimate photocatalytic activity of B-doped iron oxides in the degradation of methly orange and atrazine. The best condition to catalyze the degradation of methyl orange and atrazine was also discussed. The main results for the study were:1) B-doping can change the structure of iron oxides, enlarge their specific surface area, and the specific surface area of B-doped goethite are larger than B-doped hematite.2) B-doping can improve Lewis acidity of the catalysts and their Lewis acidity become stronger in accordance with increasing of B-doping.3) B-doping can affect the UV and visible light absorbance of iron oxides. G-S-B2%(2% B-doped goethite using sol-gel) shows the best photocatalytic activity among B-doped goethite and H-S-B2%(2% B-doped hematite using sol-gel) shows the best photocatalytic activity among B-doped hematite. B-doped hematite has better light absorbance than B-doped goethite.4) Proper B-doping can increase UV and visible light photocatalytic activity, but the excess of B impedes photocatalytic activity of the catalysts. The order of degradation of methyl orange using B-doped goethite under UV light is:G-S-B2%>G-S-B0%>G-S-B10%, and that using B-doped hematite is:H-S-B2%>H-S-B0%>H-S-B10%. B-doped hematite show better photocatalytic activity than B-doped goethite.5) In UV light, the best degradation condition for methyl orange is pH=3 and H2O2 with H-S-B2%, and in visible light, the best degradation condition for methyl orange is pH=3 and H2O2 with G-S-B2%.6) Atrazine can be photocatalyzed by B-doped iron oxides and G-S-B2% performs the best photocatalytic activity among them. The photocatalytic degradation of atrazine follow the first-order reaction kinetics. In visible light, the best degradation condition for atrazine is:pH=3,35℃, and H2O2 with G-S-B2%.