Catalytic Decomposition Of The Dyestuffs And Papermaking Waste Water With Nanostructured Manganese Oxides As Catalysts

With the further study of nanomaterials, nanocatalysts have attracted wide-range interests. In our previous work, nanostructured manganese oxides were prepared and a brief investigation of these nano-materials as catalysts to decompose methylene blue dye was made. Based on the previous work, here further research of the kinetics ofβ-MnO₂ nanorods and Mn₃O₄ nanoparticles as catalysts to decompose methylene blue dye is conducted and the optimal kinetic equations with the dyestuffs and hydrogen peroxide concentration as the control variables are obtained. Furthermore, this catalytic method is extended from dealing with single species of dye to several species of dyes and a high concentration of simulated dyestuffs waste water with its COD similar to actual waste water is studied. The key factors of this catalytic process are investigated and optimized parameters are obtained. Under the optimal conditions, the decolourization rate of the high concentration of simulated dyestuffs waste water can be up to 96%, and the COD removal can be up to 80%. Applying this method to treat actual papermaking waste water, the COD removal can be up to about 75%. Besides, under lower pH value,β-MnO₂ nanorods as catalysts can decompose Basic Safranine dye directly. The process needs neither H₂O₂ nor heat. The results indicate that lower pH value is favorable to the catalytic degradation of Basic Safranine dye. Kinetic study of the catalytic reaction shows that the decoloration rate of Basic Safranine nearly follows the first-order kinetic formula. The mechanism of the process is also discussed through the UV-Vis and FTIR analysis. It is supposed that withβ-MnO₂ nanorods as catalysts and under lower pH value, the benzene ring structure of Basic Safranine is destroyed to yield fatty amine, NH₄⁺, CO₂, and so on.