MnO₂ Preparation And Its Activation Performance On Peroxymonosulfate

In recent years, advanced oxidation technology based on SO₄^·– has been widely concerned. It has many advantages as follows compared to ^·OH:（1） it has a higher redox potential than ^·OH,（2） The life of SO₄^·– is longer and the intermediate products is more stable;（3） SO₄^·– can play better performance in a wide range of p H and some difficult degradation of pollutants can be oxidized by SO₄^·– which ^·OH can not do. There are many ways to produce SO₄^·–,in which the method of transition metal ion activation has been the most attention of researchers. Cobalt ion shows the best catalytic effect, however, the cobalt ion is poisonous, which causes second pollution to water, and it is difficult to be recycled and reused. As a consequence, it has far-reaching meaning on researching catalyzer instead of cobalt ion. In this paper, SO₄^·– could be obtained by activating potassium monopersulfate with MnO₂. It is a prospective approach to active Oxone with MnO₂ instead of cobalt ion. Compared to cobalt ion, there are a large number of MnO₂ in nature. The price of Mn ions with low toxicity is cheaper. Meanwhile, MnO₂ has large surface area, strong adsorption capacity and catalytic activity characteristics. The type of MnO₂ categories into amorphous, crystal type and new ecotype. Amorphous MnO₂ in the production process is simple and easy to scale crystal MnO₂ production.In this paper, crystal α-MnO₂, newly formed MnO₂ and amorphous MnO₂ has been made. A amorphous MnO₂ was chosen by through the methods of FT-IR, XRD, SEM and BET. The results showed MnO₂ particles were composed by a large number of tens of nanometer MnO₂ particles. There is a wealty of hydroxyl on the surface. Specific surface area is 195.46m2/g.Taking pentachlorophenol as target pollutant, the characteristics of MnO₂ activing PMS to degradation of pentachlorophenol has been researched in this experiment. The experimental results showed that it took 60 min when the degradation rate and removal rate of TOC are 89% and 56%, respectively. And MnO₂ exhibited good activity. In the experiment considering the effect of the reaction conditions on MnO₂ activity, with the increase of the amount of MnO₂, the better degration of pentachlorophenol. In a certain range of PMS concentration, with the increase of concentration of PMS and degradation of pentachlorophenol effect more obvious, in the PMS=1mmol/L,pentachlorophenol 30 min has reached 100% degradation. The temperature has promoting effect on pentachlorophenol degradation, as the temperature is increased, the degradation rate increased gradually in the PCP. The effect of water quality on MnO₂ activity also discussed in this paper. The results showed that in the water environment, pentachlorophenol removal effect obviously compared with distilled water good. This is because tap water quality environment than distilled water complex, containing the active MnO₂ promote or inhibit the cations and anions. The results of experiment with free radicals category showed that there exist SO₄^·– and ^·OH in the system at the same time. The catalyst can be reused for 4 times, and the catalytic effect was reduced from 89% to 66%, effect of catalytic reuse 2 to 3 times. After kinetic model fitting and calculation, the results showed that the degradation follow the pseudo first- order kinetics equation.