Degradation Of Dve Wastewater In An Plasma-solution System (Gliding Discharge)

Effluents from the textile industry present strong colouring, high chemical oxygen demand (COD) and severe biotoxicity, constituting a major threat to the surrounding ecosystem and human healthy. In this work a new type of giliding arc discharge device (GAD) was designed to treat dye, the objectives of the current research incolved as follows:A plasma-solution system was applied to the degradation of Acid Orange7(AO7). The effects of the initial concentration, the type of feed gases (air, oxygen, nitrogen or argon) and postdischarge phenomenon were studied. As the initial concentration increased from100mg/L to160mg/L, the degradation rate of AO7decreased from99.3%to95.9%, whereas the COD removal rate decreased from37.9%to22.6%. The degradation reaction was shown to follow pseudo-first-order kinetics. Air provided the best degradation and COD removal rates (99.3%and37.9%, respectively), followed by N2、O2and Ar. The treated AO7solution was kept for an incubation time (0,3and5day) out of discharge in the dark. A noticeable evolution of the solution COD value was seen. Since the lifetime of HO radicals is short, the increase in COD removal efficiency can be ascribed to dissolved hydrogen peroxide and to nitrites. The degradation products were analysed by a GC-MS, revealing that the degradation of the dye molecule was initiated through the cleavage of the-N=N-bond before finally being converted to organic acids.A plasma-solution system of gliding arc discharge (GAD) with zero-valent iron (ZVI) was proposed. Hydrogen peroxide generated in the solution during the discharge could combine with ZVI to induce the Fenton reaction. The optimum dosage of the ZVI was obtained with the initial Acid Orange7(AO7) concentration of200mg/L and the dosage of ZVI from0to13g. The result showed that10g ZVI results in the best degradation rate of97.8%. The degradation reaction of AO7was followed by pseudo-first-order kinetics. The rate constants for the process of GAD with ZVI was increase by12.9%,31.0%,39.4%,44.3%and47.8%with the initial centration of100,150,200,250and300mg/L respectively. The COD removal rate of A07also showed high referential value with the application of ZVI. The result of SEM and XPS analysis confirmed that the surface of ZVI was involved in Fenton reaction. A mixed solution (Acid green9:AO7:Alphazurine G=1:1:1) with initial concentration of600mg/L and initial COD value of577mg/L was decomposed by the combination plasma-solution system with ZVI treatment. The degradation rate reached82.2%,75.2%and88.6%for Acid green9, AO7and Alphazurine G, whereas the COD removal rate achieved60.1%.