The Experiment Study On Treatment Of Organic Pollutants In Polluted Groundwater By Catalytic Ozonation

In the course of industrialization and city plan, some accident, witting or unmeant organic pollute result in ground water suffer from organic pollute. Organic pollutants make a bad effect to human health, especially the refractory organics with high stability. Accordingly, it is urgently needed to develop new advanced water treatment technology that is applicable in large-scale water treatment to remove refractory organics in water effectively. Owing to the great difficulty, high cost and long periods of the treatment of polluted groundwater under ground, we always pump the polluted groundwater, and then breathe it into ground after overground treatment, Remedy the environment of ground water by air sparging-soil vapor extraction at the same time.In the various of water treatment craft, advanced oxidation technology take increasing attention for it's high removing effect. But, there has some disadvantage about this technology, such as high cost of UV light, the residue of H2O2 in water and the hard reclaim of metal in homogeneous catalytic oxidation, all of these restrict the sweeping use of catalytic ozonation. Heterogeneous catalytic oxidation dose not have the aforementioned obsession, its catalyst easy detach from water, catalytic activity mainly incarnate in accelerate the decompose of ozone and the produce of·OH. Heterogeneous catalytic oxidation has a good application prospect, and it became the hot subject. Al₂O₃ with porous gross structure have the characteristic of large specific surface area, high intensity, high abrasive resistance, not easy shed when accrete with active thing. Based on above concern, a new type of Al₂O₃ catalyst loaded with Mn-Fe has been prepared to catalyze the ozonation process in water treatment. Ozone/Mn-Fe loaded Al₂O₃ system is thus developed for removing the refractory organics with high stability in water. At the same time the new catalytic ozonation technology is a high efficiency, less cost Heterogeneous catalytic oxidation.New catalysts prepared by loading transitional metal oxide onγ-Al₂O₃ are screened, evaluated and characterized. The activity of catalysts loaded with mono-component metal oxide follows the order of Mn>Fe>Cu>Ni>Ce>Co, the catalysts loading with Mn, Fe and Cu has higher activity. The quantity of metal loaded in catalysts follows the order of Ce>Cu>Mn>Co>Ni>Fe, it's obviously that the activity of catalysts and the quantity of metal loaded in catalysts are not show direct ratio. Comparing with theγ-Al₂O₃ carrier's SEM figure, we will found that there has more crystalloid on the surface of catalysts which loading with Cu and Fe, and there has sinter of the surface of catalysts which loading with Ni, Ce, Co and Mn.The activity of catalysts loaded with bi-component metal oxide follows the order of Mn-Fe>Mn-Cu>Cu-Fe>Mn-Ni >Mn-Co>Mn-Ce. The catalysts loaded with bi-component metal oxide with manganese composition have higher activity than mono-component metal oxide. Catalysts prepared by cuprum and iron compound with manganese have higher activity than other catalysts loaded with bi-component metal oxide.γ-Al₂O₃ loaded with Mn-Fe are found to be the effective catalyst by screening and evaluating process. The proper catalyst preparing condition is also found:γ-Al₂O₃ carrier loaded with Mn-Fe metal oxide by impregnation method,γ-Al₂O₃ be impregnated into nitrate liquor of manganese and iron (metal element account for about 10%), the concentration of Mn:Fe is 2:1, calcinations temperature is 500℃and calcinations time is 6 hour. SEM-EDS characterize suggest that there is obvious interaction during loading with manganese and iron. When Mn:Fe is 2:1 in impregnation liquor ,the respectively loading quantity of Mn and Fe are 6.25% and 9.42%, higher than both mono-component and other inverse proportion. Catalyst loading with Mn and Fe(Mn:Fe=2:1) has a higher activity, the removal efficiency of nitrobenzene is 62.56%, increased by 37% compared withγ-Al₂O₃ catalyzed ozonation.Semi-continuous flow process is adopted in the experiments to study the effectiveness and mechanism of ozone/γ-Al₂O₃ loaded with Mn and Fe toward nitrobenzene and aniline removing in water. The conclusion as follows:Ozone/γ-Al₂O₃ loaded with Mn and Fe has a higher catalyze activity in degradating nitrobenzene and aniline, in ozone system the removal ratio of nitrobenzene and aniline is 86.4% and 25.56%, but the removal ratio of nitrobenzene and aniline increased by 7.5% and 37.5% at the presence of ceramic honeycombs compared with the system of ozone alone, and the removal ratio following catalyst dosage. It is found that catalyst have quite low absorbability toward nitrobenzene and aniline, and there has desorption. It was found that in heterogeneous catalytic ozonation process, the catalytic ozonation effectiveness of organic pollutants is not simple overlapping, the organic pollutants were further decomposed by catalytic oxidation after adsorbed on the catalyst. ozone dosage, initial concentration, temperature in the reaction system, solution pH has affect to oxidation system.New crystal texture formed onγ-Al₂O₃ surface after loaded with metal oxide on it. Metal oxide highly diffused to the framework ofγ-Al₂O₃, there are plenty of surface hydroxyl on the surface of catalyst, the degradation of nitrobenzene and aniline by Mn-Fe loadedγ-Al₂O₃ catalyzed ozonation process may follow hydroxyl radical mechanism.Stimulant aniline waste water,nitrobenzene waste water and BTEX waste water were confected to treated by Mn-Fe/γ-Al₂O₃ catalytic ozonation technology. It is found that uninterrupted catalytic ozonation has a good effect on treating aniline waste water, nitrobenzene waste water and BTEX waste water. The activity of catalyst is jarless , less losing under hydraulic impact, and have a good intensity.It is difficult to drastically removal the TOC and COD in water by heterogeneous catalytic oxidation, can not reach the aim of drastically removal pollutants. The mid- production made during catalytic ozonation process can stop the farther oxidation. We can make the ozone equipment removable, and catalytic oxidation can removal organic compound in short time, so many times catalytic oxidation be used as lash-up equipment or pretreatment in treatment process.