MnO₂-Mediated Mechanochemical Method To Simultaneously Degrade Decabromodiphenyl Ether Solidwaste And Prepare Active MnO_x Catalysts

Mechano-chemistry is a chemical method that was more and more popular in a little more than a decade,the applications on the organic solid waste disposal and catalyst preparation have both achieved positive results,also has provided broad technical support for conservation of environment and resource,and the key problems that retards their application is the selection of grinding agent.In this paper,we used commercial MnO₂ as a ball mill grinding agent to degrade BDE209 and simultaneously prepared MnO_x catalyst with high catalytic activity.At first,we used commercial MnO₂ to oxidatively degrade BDE209,compared with the the traditional grinding additive CaO and oxidized grinding agent Bi₂O₃ and PS,MnO₂showed better efficiency.Under the condition of 350 rpm,n_MnO2/n_BDE209=100,95.5%of initial BDE209 was removed after 2h of ball milling,and the debromination efficiency was95%.Also the apparent rate constant k_apppp was increased as the MnO₂ dosage increased,but then_MnO2/n_BDE209normalized apparent rate constant kapp’rose linearly as then_MnO2/n_BDE209varied from 40 to 100,and then almost remained constant in then_MnO2/n_BDE209range from100 and 140.In addition,to track the fate of organic carbon,we used HPLC to analysis the polar organic components and NaOH solution to absorb the generated CO₂,the results showed that BDE209 was oxidized to open the ring and organic carbon was transformed to CO₂ and carbonate.By using different pretreatment methods,the different valence state of manganese content was being analyzed,the ratio of Mn⁴⁺/Mn_tolol was increased slightly fistly,and then decreased significantly,the ratio of Mn³⁺/Mn_tolol was decreased initially,and increased gradually after 15 min,the ratio of Mn²⁺/Mn_tolol was increased continually and then almost remained a constant value.At the same time,we studied the effect of oxygen on the degradation efficiency,found that it was the lattice oxygen not oxygen gas that invoved in the reaction.At last,according to the above test results,we put forward the MC degradation mechanism of BDE209 on MnO₂.Considering the good catalytic oxidation activity of manganese oxide,we used the ball-milling product MnO_x to catalysis-oxidatively degrade phenol in the second part.First of all,we investigated the catalytic activity of the MnO_x and found that it can activate the PMS to completely gegrade phenol in a relatively short period of time.Secondly,we optimized the experimental conditions,including initial concentration of phenol,dosage of catalyst and PMS dosage.The results showed that when the catalyst dosage is 0.5 g/L,oxidant dosage is 0.5 g/L,25 mg/L phenol can be completely degraded in 10 minutes.In addition,we studied the influence of reaction temperature on the catalytic activation system,found that the higher the temperature,the greater the reaction rate constant,and the reaction activation energy is 59.7 kJ/mol.Finally,we identified the active species,found that it was singlet oxygen ¹O₂ which is catalytic species during catalysis process.