Study On Mass Transfer Process Of Ozone Aeration Of PTFE Hollow Fiber Membrane

The main factor to achieve the efficient mass transfer of ozone in liquid phase is aeration.During the process of aeration,the gas-liquid mass transfer of ozone relay on bubble,that is to say,the closely relation exists between bubble size and mass transfer.In the investigation,the mass transfer process of ozone in water was described by bubble size distribution and mass transfer coefficient based on the ozone aeration generated by PTFE hollow fiber membrane with microporous structure,and then the introduction of ultrasonic into the above system was applied to research the enhancement of mass transfer.Besides,the enhancement mechanism of mass transfer and the treatment of wastewater were also covered in this study.The bubble size distribution induced by PTFE hollow fiber membrane was studied via image-based technique.The results were clearly demonstrated that the mean bubble diameter was varied from 36.4?m to 51.8?m at the gas flow of 100L/h-500L/h,and the bubble size increased with membrane diameter.The mean bubble size produced by hydrophilic membrane was less than that produced by hydrophobic membrane due to the difference of membrane wettability.Meanwhile,the bubble performance induced by membrane was better than that induced by microporous aerator.Furthermore,the reduction of surface tension and the increase of viscosity and salinity in liquid would cause the reduction of bubble size,it was mainly due to that the variations of liquid-phase property would affect the role of coalescence among bubbles.According to the research of ozone aeration based on PTFE hollow fiber membrane,the conclusions could be drew as following:the ozone concentration in liquid and the KLa value of 0.438min-1 both reached their own highest at the gas flow of 300L/h.The increase of temperature was adverse to the efficiency of ozone mass transfer,the KLa value at the warming temperature was half of that at ambient temperature.Both the ozone concentration in liquid phase and mass transfer coefficient were reduced with the increase of membrane pore size.Besides,the aeration performance generated by hydrophobic membrane was better than that generated by hydrophilic membrane.Moreover,the ozone mass transfer efficiency produced by PTFE hollow fiber aeration was obvious higher than that produced by microporous aeration,and KLa value of the former is almost 2.2 times of the latter.In the PTFE hollow fiber membrane operation system,the enhancement of gas-liquid mass transfer was due to the increase of pressure.Moreover,the ultrasonic worked as an enhanced method was added into the above-mentioned operation system,the conclusions have been made as following:after the introduction of ultrasonic,the ozone concentration in liquid and the KLa value were increased by 34.7%-54.4%and 38%,respectively.What's more,the increase of temperature was adverse to the efficiency of ozone mass transfer.Compared with the condition of ambient temperature,the ozone concentration and KLa could be slashed by up to 68%and 71%,respectively.When the ultrasonic power was 1000W,the ozone mass transfer efficiency reached the best,and the ozone concentration and KLa could be increased by 58.6%and 30.7%as compared to the alone ozone system.Based on the study results of simulated dyestuffs wastewater treatment,the conclusions could be drew as following:the decolorization rate of wastewater could quickly reach 100%during the coupling system,at the same time the dosage of ozone could save 50%.The decolorizing reaction rate constants k were 0.372min-1 and 0.253 min-1 for combined and single system,respectively.During the degradation process of wastewater,the introduction of ultrasonic could strengthen the oxidation ability of ozone and improve the degradation rate of wastewater.