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Research on the Performance of Iron Silicate in Catalytic Ozonation of Several Organic Pollutants in

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Tutor: ShenJiMin
School: Harbin Institute of Technology
Course: Municipal Engineering
Keywords: iron silicate,catalyzed ozonation,ozone mass transfer efficiency,atrazine,nitrob
CLC: TU991.2
Type: Master's thesis
Year:  2012
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Abstract:
A lot of artificial synthesis organic matter are produced due to the rapiddevelopment of industry.These organic matter mainly include Persistent OrganicPollutants(POPs), Endocrine Disrupting Chemicals(EDCs), Pharmaceutical andPersonal Care Products£¨PPCPs£©and so on. The routine water disposing technique isusually less effective on the removal of these organic matter. Therefore, in order toensure the health and safety of drinking water, researchers have developed a numberof enhanced treatment technologies.Heterogeneous catalytic ozonation technology, as a new form of advancedoxidation processes (AOPs), combine the strong oxidizing ability of ozone with theadsorption¡¢oxidation ability of catalyst, and as the advanced treatment technologyof drinking water, heterogeneous catalytic ozonation technology has a goodprocessing effect on the removal on synthetic organic compounds in drinking water.In this article, the iron silicate which combined FeOOH¡¯s good catalytic activity andsilica sol¡¯s good mechanical strength, high specific surface area was synthesized bysol-gel method.Synthetic iron silicate¡¯s physical and chemical characteristics of wereresearched, the results showed that the iron silicate material contained a number ofnanoscale oxide particles which dispersed evenly. The iron silicate material¡¯ssurface contained surface hydroxyl groups and adsorbed water, and its surface pointof zero charge was close to neutral. Iron silicate, which was mesoporous materialsand containded a lot of mesoporous, had a larger adsorption capacity of gas.Atrazine, nitrobenzene and norfloxacin were selected as target pollutants, thecatalytic activity of iron silicate/O3system on these three different targets wasinvestigated in static conditions(Deionized water)and continuous flowconditions(tap water)respectively. The results showed that iron silicate was able tosignificantly improve the ozone¡¯s decomposition rate, particularly in the neutralcondition; iron silicate had poor adsorption effect on atrazine and nitrobenzene, butit had good catalytic activity on these two target pollutants, compared with thesingle ozonation, the removal rate of atrazine and nitrobenzene increased by27%and35%respectively under static experiment£¬and the removal rate increased by30%and28%respectively in continuous flow experiment; the mineralization degree ofatrazine and nitrobenzene in both single ozonation and catalytic ozonation were lessthan10%owing to the generation of large amout of the refractory intermediates;iron silicate had a well adsorption effect on norfloxacin, and the removal rate couldreach more than99%under ozonation alone and catalytic ozonation respectively£» iron silicate can significantly improve the effect of degradation of organic matter,and the target mineralization rate could increase by about20%.The factors affecting the removal of the target compound by iron silicate/O3system were investigated, the results showed: the removal rate of target compound,to a certain extent, increased with the rise of ozone and catalyst dosage, anddecreased with rise of target compound¡¯s concentration, the catalyst showed highcatalytic activity under different water matrix. The catalytic ozonation process ofiron silicate followed the hydroxyl radical mechanism through the influence bybicarbonate and tert-butanolon the catalytic activity was investigated, the process ofcatalytic ozonation was possiblely that ozone firstly reacted with the surfacehydroxyl groups of catalyst, and then active species such as OH were produced,these OH reacted with the target compounds in the surface of catalyst and water,lastly, the target compounds were degradation. The concentration of leaching iron ofcatalytic ozonation process under static experiment and continuous flow experimentwas able to meet the demand of national drinking water standard, as well as underdifferent pH conditions.
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