Treatment Of Simulated Developing Wastewater By Wet Air Oxidation

Photosensitive wastewater contains many undegradable and bio-toxic substances,such as HW16, which is included in National Hazardous Waste List. The present workfocused on the application of Wet Air Oxidation in the treatment of simulated developingwastewater prepared with metol. Additionally, the influence factors and mechanism ofdegradation were investigated. This work would provide new ideas for the practicalapplication of Wet Air Oxidation in the treatment of the actual developing wastewater.In order to determine the optimum degradation conditions, the COD removalefficiency was set as the technical indicators, and the impact of several parameters on thedegradation of metol, such as the reaction temperature, the oxygen partial pressure ofreaction, the initial pH, stirring rate, and initial concentration of metol, were investigated,respectively. The results show that the wet air oxidation treatment indicated significanteffect for the removal of metol. Under the optimal reaction conditions, while running for60min, the COD removal efficiency reached85.1%. Whilst, results show that temperatureis the main inpact factor on the removal efficiency of metol by the wet air oxidation,namely, the effect of wet air oxidation treatment was improved significant as theincreasing of temperature. And result also shows that the oxidative degradation of metol isin favor of the acidic conditions. However, the oxygen partial pressure and stirring rateexhibited less influence on the degradation of metol, but they can effectively improve thereaction rate during the initial stage. When the concentration of metol is6.00g/L, theoptimal reaction conditions are as follows: reaction temperature is180℃, the oxygenpartial pressure is1.6MPa, the initial pH value is3.91(ie6.00g/L metol solution originalpH), stirring rate is300r/min.In order to explore the mechanism of the degradation of metol, the samples wereanalysed by LC-MS. And the results indicated that in the WAO system, metol hasundergone polymerization, dehydration, and hydrogenation consecutively, and eventually,metol was degraded into the polymer, quinines, phenols and some kinds of carboxylicacids and other substances.