Research On The Treatment Of CEH Bleaching Effluent By Photocatalysis With TiO₂

Many Chinese paper and pulp industry are still using traditional CEH bleaching process, the wastewater which they discharge every year not only includes a large amount of COD and BOD, but also carcinogens materials, such as chlorophynols etc. Recently, the advanced oxygen process (AOPs), UV/TiO2, has become one of the most popular and welcome technologies in dealing with wastewater. UV/TiO2 can degrade most of the organic and inorganic materials in wastewater in a cheap and easy way, moreover it will degrade the pollutants into water, carbonate dioxide and related nonpoisonous organic. Because of its nonpoisonous and stable characteristics, TiO2 has become the most attractive mental oxide. This paper contains three main aspects. First, assure the optimum reaction parameters; second, study the change of chlorophenols in the CEH bleaching effluent during reaction; third, study on dynamics of 2, 4-dichlorophynol degradation.The conclusions:1. The optimum reaction parameters are: pH=12, TiO2 concentration 0.5g/L, reaction time 12h and aerating oxygen. Under the conditions, CODcr degradation ratio is 92% and decolorization ratio is 89.4%.2. Using UV-Vis spectrometry and GC-MS to analyze and compare the change of chlorophynols in the CEH bleaching effluent between the raw wastewater and the solution after reacting 12h. In the raw wastewater we find 2,4 — dichlorophynol, 2, 4, 6- trichlorophynol and pentachlorophenol, which take up 5.53%, 2. 90% and 14. 47% respectively, totally22.90%. In the same time, some other organics have been detected such as dibutyl phthalate et al. After photocatalytic degrading 12h, we could hardly find both chlorophynols and other organics.3. Study on the dynamics of 2,4-dichlorophynol degradation. The velocity equation follows zero order kinetics when the concentrations of 2,4-dichlorophynol ranges from 150mg/L to 50mg/L; and follow first dynamics when the concentrations of 2,4-dichlorophynol ranges from 25mg/L to 5mg/L. The velocity constants (kapp) of first order kinetics fall down with the concentrations of 2,4-dichlorophynol rising. In the same time, half lives (tO. 5) prolong. TiO2 concentration and pH value do dramatically effects to the degradation of 2,4-dichlorophynol. The optimum parameters are: pH is 11 and TiO2 concentration is 1g/L.