Treatment Of Rhodamine B Printing And Dyeing Wastewater By O₃/UV Processes In A Rotating Packed Bed

As a pillar sector in China,the printing and dyeing industry produces large amounts of wastewater with complex constituents and high chromaticity,so it is difficult to degrade the wastewater effectively by traditional treatment methods.The advanced oxidation process(AOP)can generate highly oxidizing free radicals,which can degrade pollutants to inorganic matters efficiently.Therefore,AOP is suitable for wastewater treatment.In this thesis,the high-gravity technology and AOP was combined to study the degradation of the printing and dyeing wastewater of Rhodamine B by the UV,O3 and O3/UV processes.The effect of various operating conditions on decolorization and COD removal of the wastewater was investigated,and the effect of the three processes was compared to determine the most suitable process.The main research results are as follows:(1)The Rhodamine B wastewater was treated by the UV process using a stirred tank(STR)as the reactor.The effect of the initial pH of the wastewater,concentration of the catalyst P25 and reaction time on decolorization and COD removal of the wastewater was investigated.The results showed that the decolorization and COD removal percentages increased first and then decreased with the increase of initial pH,and gradually increased with the increase of catalyst P25 concentration and reaction time.(2)Rotating packed bed(RPB)was used as the reactor to treat Rhodamine B wastewater by the O3 process.The effect of RPB rotation speed,wastewater flow rate,ozone concentration,reaction temperature,and initial pH on decolorization and COD removal of the wastewater was investigated.The results showed that the decolorization and COD removal percentages of the wastewater increased first and then tended to be stable with the increase of RPB rotation speed and ozone concentration;the decolorization and COD removal percentages decreased with the increase of wastewater flow rate and initial pH.The effect of reaction temperature on decolorization and COD removal was insignificant.(3)Rhodamine B wastewater was treated by the O3/UV coupling process with RPB and STR as reactors in series.The effect of RPB rotation speed,ozone concentration,concentration of catalyst P25,liquid circulation flow rate,gas flow rate and initial pH on decolorization and COD removal of the wastewater was investigated.It was found that the decolorization and COD removal percentages increased with the increase of RPB rotation speed,ozone concentration,liquid circulation flow rate and concentration of catalyst P25,and the change of gas flow had no obvious effect on decolorization and COD removal.With the increase of initial pH,the COD removal percentage of the wastewater increased first and then decreased.(4)A comparison of the above processes indicated that the O3/UV coupling process had the best treatment effect on Rhodamine B wastewater,with the decolorization and COD removal percentages reaching 100%and 40%respectively.The results revealed that the coupling of O3 and UV is conducive to the generation of hydroxyl radicals,thereby improving decolorization and COD removal.