The Study Of Degradation Of Refractory Organic Wastewater By Catalytic Wet Air Oxidation Process-the Degradation Of Azo Dyes By AC-FeCl₃/O₂System

As the major source of the industrial wastewater, textile printing and dying industrialwastewater is about35%of the total industrial wastewater emission. Its specificcharacteristics should be higher concentration of organic pollutants, deep color, alkaline,frequent and variable water quality, toxicity and low bio-degradability. Azo dye is the largestpart of synthetic dyestuff, which is almost over70%of the total dyes. Catalytic wet airoxidation （CWAO） presents a very huge potential in dye wastewater treatment because of itshigh efficiency, broad application aspects, and less secondary pollution as a brand newadvanced technology.In this study, azo dyes Methyl Orange and Reactive Red2BF were degraded by aheterogeneous CWAO system consisted of Fe/AC and O2respectively. The study results wereas follows:The optimal reaction condition of application of AC–FeCl₃/O₂system for the treatmentof azo dye Methyl Orange was: Methyl Orange concentration200mg/L, reaction temperature150℃, oxygen partial pressure0.5MPa, pH3.0, catalyst dosage4g/L, and reaction time1h,the TOC and color removal rates were92.5%and95.4%respectively; The optimalpreparation condition under the optimal reaction condition was: impregnation time4h,impregnation method ordinary method, impregnation solution concentration0.5mol/L,calcination temperature300℃, calcination time3h, drying method drying at roomtemperature for24h.The optimal reaction condition of application of AC–FeCl₃/O₂system for the treatmentof azo dye Reactive Red2BF was: Reactive Red2BF concentration400mg/L, reactiontemperature150℃, oxygen partial pressure0.5MPa, pH3.0, catalyst dosage4g/L, andreaction time1h, the TOC and color removal rates were94.2%and94.4%respectively.The reaction mechanism with the Ultraviolet-visible absorption spectrum was studied.The two different azo dyes were both degraded to a large extent, but will need more time toget the azo dyes completely degraded to improve its biodegradability. The reaction kinetics of the system for the treatment of Methyl Orange was investigated.It indicates that Methyl Orange reaction was consistant with a pseudo-first order kineticmodel. Meanwhile, its rate equation of the reaction was got.In all, AC–FeCl₃/O₂system for the treatment of the two azo dyes was efficient, whichdeveloped a new way for dye degradation. In this system, inexpensive and easily availablecatalyst and oxidant, avoidance of any organic solvents, and industrialized reactor made theAC–FeCl₃/O₂system rather competitive and promising in the practical industrial activities inthe future.