The Research On Degradation Of Nitrobenzene By Ozone/Si-FeOOH

The shortage of water resource is serious in China. As the process of accelerated modernization, water pollution has become increasingly severe. The organic pollution, especially the degradation of organic matter is difficult, has became urgent problems. Among various water treatment technologies, due to its high efficiency and effective, advanced oxidation process(AOP) has been ceceived more attention. Among them, the ozonation technology has broad application prospects. The principle of ozonation technology is that because of some factors' affection, the ozone generate free radicals (mainly hydroxyl radical HO·), and the HO·react with pollutants. Compared with ozone, the reaction rate of hydroxyl radical HO·with organic mater is greatly improved, the degradation of organic compounds could achieve satisfactory results. The tagat matter, nitrobenzene is a kind of refractory matter with high chemical stability, also a carcinogens, is hard to be degraded by ozone molecules, although the ozone is a kind of strong oxidant.This paper mainly made a research using Si-FeOOH as a catalyst, discussing the effect of ozone alone and ozone/Si-FeOOH during degradation nitrobenzene. The rate of reuse of catalyst Si-FeOOH and the reaction rate constant in ozone alone,ozone/catalyst system were analyzed too.The catalyst Si-FeOOH was prepared, and was used to instead of FeOOH, which is low mechanical strength, unstable in nature. The repeated use of Si-FeOOH and FeOOH were measured from three aspects: solution turbidity, iron dissolution and recovery rate of the catalyst. The results showed that the Si-FeOOH with Si/Fe molar ratio is 0.2 is most suitable for practical application.Influencing factors about degradation of nitrobenzene in system O3, O3/Si-FeOOH and O3/FeOOH were analyzed. The amount of catalyst, ozone dosage, catalyst with different Si/Fe molar ratio, solution initial pH, Tert-butyl alcohol(TBA), the hydroxyl radical inhibitor and the reuse of catalyst were studied. The results showed that the addition of catalyst improved the removal effect of nitrobenzene. The system of O3/FeOOH had the the best effect of nitrobenzene removal effect. The system of O3/Si-FeOOH had a poor removal effect about nitrobenzene. The system of ozone alone had a worst removal effect about nitrobenzene. As the catalyst dosage was 0.1g/L, the removal effect about nitrobenzene was the best. The Si-FeOOH with different Si/Fe molar ratio had a different removal effect of nitrobenzene. As the increasing of Si/Fe molar ratio, the removal efficiency decreased. The initial pH value of reaction solution had a great influence to the catalytic degradation of nitrobenzene. As the pH value increases, the nitrobenzene removal efficiency also increased, while the pH is 9 and pH value is 11, nitratebenzene removal effect was just the same. Tert-butyl alcohol decreased the removal effect of nitrobenzene, indicating that the catalytic reaction is mainly an indirect jprocess while hydroxyl radical is the oxidant. The reuse of Si-FeOOH had a little influence to the removal efficiency about nitrobenzene. So the Si-FeOOH can be repeated used in a reaearch. On the contrast, due to a small recovery rate of FeOOH, when the FeOOH was repeated used, the efficiency of nitrobenzene removal is very poor.The dynamic model of nitrobenzene oxidation in the system of ozone alone and ozone/catalyst was studied in this paper. The reaction rate constants of the two systems were compared, and the propotion of direct oxidation process and indirect oxidation process in its own system were also calculated. The results showed that in the system of O3 and O3/Si-FeOOH, the rate of oxidation of nitrobenzene in O3/Si-FeOOH system was significantly higher than the rate of oxidation of nitrobenzene in O3 system. While the tert-butyl alcohol was added, the two systems had a very close reaction rate constant, indicating the addition of tert-butyl alcohol effectively inhibited the indirect oxidation of hydroxyl radical HO-, and then ozone was the main oxidant in reaction process. In the system of O3,O3/Si-FeOOH, the propotion of indirect oxidation in the total reaction process was 41.7%,63.9% respectively, showing that indirect oxidation was the main degradation of nitrobenzene in the system of O3/Si-FeOOH.