Surfactant azo dyes photocatalytic oxidative degradation
|School||Tianjin Polytechnic University|
|Keywords||Azo dyes surfactant ferrioxalate degradation influence|
Treatment of dyeing water pollution is a major task of environmental protection. Among the treatment techniques,the method of H2O2/ferrioxalate photocatalytic oxidation system had drawn much attention.Three reactive dyes with azo structure including C.I.Reactive Red195,C.I. reactive blue 222 and C.I.reactive yellow 145,and three kinds of acid dyes with azo structure,including C.I.acid black 234,C.I.mordant black 9 and C.I.acid orange 156 were chosen as the model pollutants for simulative contamination in this experiment. Four kinds of surfacants namely sodium dodecylbnzene sulfonate（SDBS）,sodium lauryl sulfate（AS）,Polyoxyethylene nonyl phenyl ether（OP-10）and Tween-80 （TW-80）were also used for simulative contamination,Some factors effecting the decoloration of azo dyes such as the type and concentrations of surfactants,various light intension were examined with respect to decoloration percentage.In order to have a better insight into the degradation of azo dyes in the presence of surfactants, the method of UV-visible-spectrum was introduced to discuss the degradation of surfactant and the interaction between surfactants and azo dyes in aqueous.The results indicated that there is the significant interaction between nonioinc surfacant molecules（OP-10 and TW-80）and azo dyes,especially acid dyes.On the other hand,it is found that little interaction between anioinc surfacant molecules （SDBS and AS）and azo dyes.This is mainly becaues of the big difference in molecular structure of azo dyes.The decoloration could be limited（reduced,inhabited） in the presence of SDBS and in the concentration varying from 5-7.0mmol/L, meanwhile,the effect of limite increased with increasing the concentration of SDBS. The restraining for reactive dye 195 decoloration reached a peak when the concentration of OP-10 was 0.20mmol/L,over this concentration,the effect of restraining was reduced.The decoloration of black acid dye 234 was inhabited in the presence of OP-10 concentration under CMC,and accelerated over CMC.The degradation of azo dyes are determined by two factors,One was that the rate of H2O2 decomposing was reduced in the presence of surfactant;another was that there was competition between SAA and dyes for hydroxyl radicals.When the concentration of SAA was below CMC concentration,surfactant can be easily degradated and contested for hydroxyl radicals with dyes strongly.When the concentration of SAA was more than CMC,the degradation of surfactant was carried out with difficulty.After experiment,it could be seen that the strength of light irradiation as well as Na2SO4 couldn’t influence dyes degradation with SDBS and OP-10 respectively,but high light irradiation caused increased degradation of dyes.