Study On The Oxidative Degradation Of Catechol Compounds

Catechol compounds is a class of aromatic compounds which containing one or more catechol group structure. It not only can be found in fruits, vegetables, tobacco and some medicinal materials, and also is the common intermediate product in degrading aromatic compounds. Those compounds are widely used in chemical industry, pharmaceutical synthesis etc. As the rapid development of industrial, type and structure of these compounds tend to be complicated, the difficulty of the degradation in wastewater is increasing. If the wastewater discharged into the environment, it will threaten the survival of human, animal and plant by accumulation and diffusion. So, the degradation of phenolic compounds is an important subject in wastewater treatment.Polypyrrole (PPy) is a kind of polymer materials which has conjugated structure. It shows the good conductivity, stability and reversible redox properties. Meanwhile, simple synthesis method and environmental friendly are also important characteristics, PPy become one of the most studied the materials in recent years. In this paper, we choose simple device and method to prepare PPy nano composite materials, and it overcomes water insoluble and poor dispersibility because of the combined effects, then those composite materials are applied to study on oxidative degradation of catechol compounds. The main contents are as following:1. With nano-SiO2 and pyrrole monomer (Py) as raw materials, FeCl3 as oxidation, different proportions of Polypyrrole/nano-SiO2 composite (PPy/nSiO2) was prepared by chemical oxidative polymerization and characterized by SEM and FTIR. It was used for oxidative degradation of pyrocatechol violet. The results showed that nano-SiO2 plays a better role in dispersing PPy, it improved the oxidation activity of PPy by increasing specific surface area. Pyrocatechol violet (PCV) removal efficiency could reach 94.7% in 2 hours under the optimum experimental conditions:PCV concentration 1×10-4mol/L with 2.0mg/mL of PPy/nSiO2. And PPy/nSiO2 exhibited the catalyst properties for PCV, it was good for improving the reaction rate and reducing the dosage of PPy/nSiO2.2. With nano-MnO2 as the carrier which was fabricated using MnSO4 and KMnO4, then Polypyrrole/manganese dioxide composite (PPy/nMnO2) was synthesized by chemical oxidative polymerization. And the structure and morphology of PPy/nMnO2 was characterized by SEM, FTIR and XPS techniques. The property was studied by reacting with catechol. Meanwhile, impacts of solution pH, PPy/nMnO2 loading, H2O2 concentration and ionic strength on the degradation of catechol were studied, and the degradation pathway of catechol was discussed by UV-Visable spectrum. The results showed that polypyrrole with small spherical particle was loaded on the surface of nano-MnO2, and composite presented a state of coating. PPy/nMnO2 exhibited good catalytic oxidation performance. For 4×10-4mol/L catechol solution, with 0.5 mg/mL PPy/nMnO2 and 4×10-3mol/L H2O2, the removal rate of catechol up to 91.4% after 2 hours. In addition, the coexistence of Cl- and SO42- showed different degree of inhibition effect in the oxidative degradation process. 3. Oxidative degradation of PCV with PPy/nMnO2 was investigated. Impacts of solution pH, PPy/nMnO2 loading, common ionic were studied. The result showed that PCV degradation efficiency could reach 95.5% for the same concentration of PCV in pH=2 solution containing 0.7 mg/mL PPy/nMnO2, and PPy/nMnO2 exihibited the better oxidation performance than PPy/nSiO2.