| Among various methods for the industrial wastewater treatments, the low-temperatureplasma technology has become a research hotspot in the field of wastewater degradation becauseit can generate many oxidative species. Atmospheric pressure dielectric barrier discharge (DBD)plasma owns many advantages, such as simple operation, rapid degradation rate, no secondarypollution, and it presents a greatly potential application for water treating. In this paper, thedischarge characteristics of a novel DBD system for dye degradation were studied. Theproperties of fabricated Co3O4catalyst were analyzed. Finally, the factors affecting MOdegradation with DBD plasma and Co3O4was studied. Moreover, the possible oxidationmechanism and degradation pathways of MO were proposed.It is found that when the applied power is lower than100W and the air plasma gastemperature is lower than312K, and it is suitable for treating organic dyes at room temperature.The discharge current of DBD plasma increased with increasing applied power. In addition, theoutput voltage of plasma was not affected by the catalyst quantity dispersed in solution.According to the OES results, many reactive species such as O+2、·OH、·O were detected. Withthe increase of applied power and O2flow rate, the concentration of O3in the plasma jet wasincreased. All the reactive species played a very important role in the dye degradation process.The catalysts of Co3O4and Ag/TiO2were fabricated through hydrothermal methodsuccessfully. The crystal structure of Co3O4was characterized by XRD. Diffraction peaksdetected at31.2o,36.5o,44.8o,59.0oand65.1ocorrespond to the reflections (220),(311),(400),(511) and (440), respectively. With a higher magnification by TEM, the particles size of Co3O4was about40nm. The lattice planes of Co3O4are (311) with a lattice space of0.246nm, and(220) with a lattice space of0.285nm which may play an important catalytic role in degradationprogress. In addition, for the catalyst of Ag/TiO2, diffraction peaks in XRD spectra detected at44.3°,64.4°, and77.5°are assigned to Ag particles. These diffraction peaks correspond to thereflections (200),(220) and (311), respectively. SEM and TEM results revealed that the average diameter of TiO2was about65nm. Ag particles doped uniformly on the surface of TiO2and itsaverage diameter was about5nm.In the process of plasma degradation with Co3O4on MO, the discharge power, oxygen flowrate and catalyst have great effect on the dye degradation. Under the condition of air discharge,the degradation efficiency of MO is increased from58%to92%with increase of applied powerfrom30W to100W. When Ar flow rate and discharge power were at a certain amount, thedegradation efficiency of MO was increased from35.5%to43%with increase of O2flow ratefrom0.09m3/h to0.21m3/h. It is proved that the presence of catalysts for MO degradation has apositive effect. However, the combination of plasma radiation and Co3O4showed no effectivedegradation on MO dye. While under the function of plasma by-products (O3) and Co3O4, theMO degradation rate reached86%after18min treatment. In addition, when air flow rate anddischarge power were at a certain amount, the degradation efficiency of MO was increased from35%to56%with increase of O2flow rate from0.05m3/h to0.20m3/h. And under the function ofplasma by-products (O3) and Ag/TiO2, the MO degradation rate reached95%after6mintreatment. finally, the possible oxidation mechanism and degradation pathways of MO dye usingthe plasma were proposed... |
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