The Treatment Study On Printing Wastewater By Potassium Ferrate

The printing and dyeing wastewater is difficult to treat, because of its characteristics, such as deep chromaticity, high concentration organic pollutant, complex ingredient, and high content of COD. In domestic and overseas areas at present, commonly used method cannot effectively deal with both hydrophobic and hydrophilic dye printing and dyeing wastewater. In order to effectively deal with both hydrophobic and hydrophilic dye printing and dyeing wastewater, potassium ferrate is used in this paper.In this paper, reactive dyes are selected as a class of hydrophilic, disperse dyes are selected as a class of hydrophobic, then the effects of potassium ferrate treating reactive dye wastewater,disperse dye wastewater and mixed dye wastewater are studied. The results of tins experiment showed that: the removel efficiency is accelerated with increasing ferrate potassium dosing quantity. Removal efficiency of chromaticity is good, reaching above 90%, while removal efficiency of COD is not ideal. Removal efficiency of reactive dyes wastewater COD is less than 50%; removal efficiency of disperse dyes wastewater COD is better than purely reactive dyes wastewater COD, reaching to 80%. Printing and dyeing wastewater treatment effect is best when the pH value is controlled between 7 and 8. Treatment effect of reactive dyes wastewater is optimal when pH value is controlled between 6 and 8; removal efficiency of disperse dyes wastewater is accelerated with increasing pH value, this experiment is processing under the pH value is greater than or equal to 6. The removal rate of chromaticity and COD would rise with the prolonging of reacting time. Because of the different reaction mechanism of ferrate potassium treating dyeing wastewater, the removal effect is different in every operation group. For reactive dyes, when the reaction time is 0-5min, wastewater chromaticity changes quickly and removal efficiency high, but COD changes slowly and removal efficiency low; when the reaction time is 5-10min, COD changes quickly and removal efficiency high, but wastewater chromaticity changes slowly and removal efficiency low; when the reaction time reaches to 20min, chromaticity and COD change are both stable. For disperse dyes, when the reaction time is 0-5min, the removal rate of chromaticity and COD are low; when the reaction time is 5-10min, the removal rate of chromaticity and COD rise quickly; when the reaction time reaches to 20min, chromaticity and COD change are both stable.At last, potassium ferrate preoxidation enhanced coagulation process is used to deeply treat mixed dye wastewater, then this method is used to the actual printing and dyeing wastewater for discussing treatment effect.The results of tins experiment showed that: the comparative study results of ferric chloride and ferrate potassium joined method with vitriolic and ferrate potassium joined method show that vitriolic and ferrate potassium joined method is better, the removal rate of chromaticity is 98.72%, the removal rate of COD is 89.26%. Treatment effect is best when aluminum sulfate dosage is 15 mg/L, pH is between 6 and 7 during coagulation, coagulation stirring speed is 60r/min, mixing time is 20min, sediment time is 40min.The removel efficiency of chromaticity and COD in actual wastwater is better by ferrate potassium and vitriolic joined, could be applied to production practice.Draw a conclusion: chromaticity of hydrophilic and hydrophobic dyes wastewater could be removed by ferrate potassium; COD could be efficiently removed by ferrate potassium and vitriolic joined.