Study On The Kinetics Of Degradation Of Dye Wastewater By Atmospheric Pressure Glow Discharge

Based on the background of dye-containing wastewater can not be well treated by troditional degradation processes,the advanced oxidation technology of atmospheric pressure glow discharge plasma is used for dye wastewater treatment.It is found that the mechanism of the advanced oxidation technology for wastewater treatment and the influence of various factors on the treatment efficiency are not clear.In this paper,safranine T,malachite green(MG)and orange ? were used as the study object treated using atmospheric pressure glow discharge plasma.It is explored that various active species produced during glow discharge plasma by using emission spectroscopy.The effect of controlled experiment parameters on the degradation efficiency was investigated by using the change of the absorbance at the characteristic absorption wavelength,and the influence rule of each parameter was analyzed.In order to getting deep understanding of the relationship between the molecule structure and property,the vibrational spectra of MG and orange ? two molecules were measured,calculated and identified.Finally,the degradation process of the two dye molecules was forecasted comprehensively from three aspects including the generation of active particles,the change of UV-visible spectrum and the theoretical calculation.The main conclusions of the research are as follows:(1)Taking safranine T as the research object,this paper explores the active species generated by the discharge process and played a major role in the degradation of safranine T,electron temperature and density of plasma.By measuring the emission spectra of the plasma channel,it was found that there are a large number of active species,such as ·OH,N2+,O2+,·H etc.in the discharge channel,and ·OH is mainly responsible for the degradation of safranine T.The physical parameters of the plasma were also diagnosed,the electron excitation temperatures calculated using the hydrogen atom emission spectrum(H?,H?)were in the range 6500K-8500K,and the orders of electron density calculated by using Stark broadening were 1017cm-3-1018cm-3.(2)Using malachite green as the research object,the experiment investigated several factors may influencing the degradation of MG during discharge treatment,such as discharge voltage,initial concentration,initial PH,different cation and anion etc..it was found that the degradation efficiency is the higher under these conditions such as the higher the discharge voltage,the lower the initial concentration and the initial pH value.The degradation process of MG satisfies the first order kinetic equation.The addition of appropriate amount of Cu2+?Fe2+and Fe3+ promoted the degradation of MG.However,the addition of same amount of SO42-?Cl-?CO31-inhibited the degradation of MG,and inhibition descending order of CO32->Cl>SO42-.(3)The orange ? was selected as the object of study.Firstly,the effects of discharge voltage,initial concentration and conductivity of original solution on the degradation of orange ?were investigated.Secondly,it's been focused on the experimental conditions and degradation effect of orange ? under the synergistic action of discharge plasma and Fenton effect.And the degradation effect under synergistic conditions and separated discharge conditions were comparatively investigated.In the case of a single discharge or synergistic effect with Fenton,the lower the PH,the higher the degradation rate.The proper additionof H2O2 and Fe2+ in the wastewater can promote the degradation of dye wastewater,but the excessive addition will inhibit degradation rate.(4)The vibrational spectra of MG and orange?were calculated by Gaussian09 software.The functional groups and vibration forms for the normal vibration with greater intensity were identified and compared with the experimental infrared spectra(KBr pellet)and Raman spectroscopy.The results show that the frequency values of theoretical calculations are in good agreement with the experimental measurements.(5)The natural bond orbital(NBO)analysis of MG and orange ? molecules was carried out by B3LYP/6-311(d,p)method using the keyword Bndidx,it is found that the weaker Wiberg bond orders are C=C and C-N for MG molecule,and C-S,C-O,S-O and C-N for orange ?.The weaker Wiberg chemistry bond is easily broken in degradation process,followed by the C-C bond of benzene and naphthalene ring is opened.