Study On Advanced Oxidation Process For Lab Effluents Treatment

Lab effluents have posed a great threat to the environment; however, so far there have been only few reports to study their treatment. The components of lab effluents are quite complicated and changeable, including plenty of poisonous and bio-recalcitrant pollutants. Advanced Oxidation Process is an effective, economical, safe and reliable technology for wastewater treatment. And many poisonous and bio-recalcitrant pollutants can be efficiently degraded and even total mineralized by advanced oxidation process. Therefore, advance oxidation process is a suitable technology for lab effluents treatment.In this thesis, ozone oxidation system and heterogeneous photocatalysis system were introduced for lab effluents treatment.Phenol was chosen as a model pollutant to determine the oxidation efficiency of ozone. The results showed that original pH of the wastewater had a great influence on both the efficiency of phenol removal and the efficiency of ozone consumption. The two efficiencies could be both ordered as pH = 10.3 > pH = 11.3> pH = 9.3> pH = 6.2 > pH = 3.2 (the initial concentration of phenol was 10 mg/L and the gas flux was 1.6 L/min). The gas flux could exert a complicated influence on the efficiency of phenol removal, and the final results indicated that the efficiency could be ordered as Q = 1.6 L/min > Q = 1.0 L/min> Q = 0.4 L/min ( Q denotes the gas flux), when the initial concentration of phenol was 10 mg/L and the initial pH value was 10.3.The gas flux also had a pronounced effect on the efficiency of ozone consumption, andthe general efficiency order was Q = 1.6 L/min> Q = 1.0 L/min > Q = 0.4 L/min, when the initial concentration of phenol was 10 mg/L and the initial pH value was 10.3.TiO2 has attracted increasing attention for its promising prospect in decomposition of various environmental pollutants in both gaseous and liquid phase. Development of TiO2 photocatalysts anchored on supporting materials with large surface areas, by which dilute polluted substances can be condensed, would be of great significance, not only to avoid the disadvantage of separation of fine TiO2 photocatalyst particles, but to lead to high photodecomposition efficiency.Activated Carbon Fibers (ACFs), a new formulation of activated carbon, are produced in the form of felt or cloth, which would be an advantage of separation. Additionally, ACFs have larger adsorption capacity and greater rates of adsorption and desorption process. Nevertheless, so far there have been only a few reports to study preparation methods and photodegradation behavior of loading TiO2 photocatalysts on ACFs. Reported methods of depositing TiO2 photocatalysts on ACFs include an ionized cluster beam, a sol-gel method and a pasting treatment. Inthis study, a new, simple and effective method ------ hydrolysis of titaniumtetrachloride (TiCI4) was found to prepare ACFs supported TiO2 photocatalysts. The morphology of TiO2 deposited on ACFs was observed by SEM. The results showed that TiO2 were fixed on the surface of ACFs in particles, and some of these particles aggregated into clusters .The size of the particles was under 100 um. Certain amount of carbon fibers'surface was still exposed in this photocatalyst. The heat treatment in N2 atmosphere successfully avoided damage caused by being calcined in oxygen atmosphere to the surface porous structure of ACFs.Rhodamine B was chosen as the model pollutant to determine the photocatalytic efficiency of the ACFs supported TiO2 photocatalysts. In order to demonstrate the greater oxidizing power of the photocatalytic system and to quantify the additional levels of degradation attained, experiments were performed on the oxidation of Rhodamine B by UV radiation alone and by the TiO₂/ACFs/UV radiation combination. A kinetic model was applied for the photo oxidation by UV radiationand by the TiCVACFs/UV system. Experimental results indicated that the kinetics for both oxidation processes could be fitted well by a pseudo-first-order kinetic model. A comparison between the kinetic rate constants for two oxidation systems revealed that the constants for the TiCVACFs/UV system were clearly greater than those obtained in the direct UV photo oxidation.In addition, comparison of three Rhodamine B removal processes, namely, photocatalytic decomposition by the TiCVACFs photocatalysts, photolysis and adsorption of unmodified ACFs, and photocatalytic decomposition with Nano-sized TiC>2 powder, was carried out. The results showed that the efficiency of photocatalytic degradation of Rhodamine B with the prepared photocatalysts was higher than that of the photolysis and adsorption of the unmodified ACFs, as well as that of Nano-sized TiC>2 powder. The photodecomposition efficiency of Rhodamine B with TiCVACFs photocatalysts remained almost the same with the coating time added. Moreover, cyclic usage is possible for the produced TiCVACFs photocatalysts, since the photocatalytic reactivity of the reused photocatalyst was just slightly reduced, compared with the fresh one. The photocatalytic efficiency improved as the added amount of TiCVACFs increased, and the maximum added amount in this study was 1.0487 g for 50 ml Rhodamine B with the initial concentration of 150 mg/L.Besides, it was found that the initial pH of the Rhodamine B aqueous solution also had a noticeable influence on the photodegradation efficiency of TiCVACFs photocatalysts. The photocatalytic efficiency shown in the results could be ordered as pH2.0 > pH5.1 > pH7.0 > pH12.5 >pH9.0. It was observed in this study that the photocatalytic reactivity of the TiCVACFs photocatalysts was enhanced with the UV light intensity increased. The calculated pseudo-first-order kinetic rate constants for the photocatalytic degradation of Rhodamine B were 0.0031 min"1 under the irradiation of 40 w UV lamp and 0.0057 min"1 under the irradiation of two 40 w UV lamps, respectively.In this thesis, a preliminary study on the ozone oxidation system and heterogeneous photocatalysis system for lab effluents treatment were finished. The preparation method of loading TiC>2 photocatalysts on ACFs was found, and thefundamental path for applying advanced oxidation process to treating lab effluentswas built.