The Degradation Of Ciprofloxacin By The Advanced Photochemical Processes Using Microwave Discharge Electrodeless Lamp

The study was based on a novel UV light source-microwave electrodeless lamp (MWEDL) which can emit vacuum ultraviolet light185nm and193nm and high strength UVC254nm light, and developed a series of photochemical advanced oxidation processes:MWEDL photolysis (MW/UV), MWEDL/hydrogen peroxide (MW/UV/H2O2), MWEDL/hydrogen peroxide/Fe2+(MW/UV/H2O2/Fe2+) and MWEDL/TiO2(MW/UV/TiO2). These four systems used for the completely degradation of an antibiotic ciprofloxacin substances in water, which can provide new alternatives for the treatment of organic pollutants in water. This thesis has studied the dynamics characteristics of CIP degradation, the degradation kinetics in different gas condition, and the effect of the initial CIP concentration, the initial pH, aeration rate, H2O2dosage, Fe2+dosage, TiO2dosage on CIP degradation in different processes were discussed, the CIP degradation processes and reaction mechanisms were also investigated. The results show that:1) In the absence of additional oxidant, MW/UV system can degrade CIP rapidly in water. The degradation has been significantly influence on by the bubbled gases, such as when the250mL100mg/L CIP were degraded by the MW/UV process, the degradation rate of CIP was46.4%,89.3%and98.4%for the N2, Air, O2, respectively. CIP degradation under different conditions followed with pseudo first order reaction kinetics, and the rate constants were0.0052min-1(N2),0.0170min-1(Air) and0.0233min-1(O2), respectively; the MW/UV system also can realize the mineralization of CIP, in N2, Air, O2conditions the TOC removal were21.1%,54.1%and64%, respectively. Acidic conditions were more conducive to CIP mineralization, the higher initial concentration and less gas bubbled flow rate, the lower was the degradation rate. At last we obtained the optimum parameters: pH=3.0, aeration rate of0.6L/min, reaction time120min. About the reaction mechanism, the high concentrations of hydroxyl radical and H2O2generated were detected in the MW/UV system, which indicates the vacuum ultraviolet from MWEDL can react water molecules to produce high activity·OH, which can realize the efficient degradation of organic compounds in the water. 2) Based on the above MW/UV process, H2O2was added to the system and forming a MW/UV/H2O2process, which can greatly increase the degradation rate of CIP, when the reaction condition is pH=3.0, aeration rate was0.6L/min and the dosage of H2O2is5.28mM, the degradation rate in the N2, Air, O2bubbling condition, the CIP degradation rate can reached98.6%,98.7%and99.2%respectively; the degradation the processes also followed the pseudo first order reaction kinetics, the reaction rate constant were:0.0751min-1(N2),0.1088min-1(Air) and0.1475min-1(O2); In this process, the TOC removal rate of were43.2%,62.9%and78.7%, respectively.3) The ferrous ion was Introduced into the above MW/UV/H2O2system forming Mw/UV/H2O2/Fe2+system, in this process, the CIP degradation by the synergistic photo-Fenton and VUV process was more completely. In the initial100mg/L CIP, pH=3.0, aeration rate was0.6L/min, H2O2dosage2.64mM, Fe2+was0.1mM, reaction time120min, TOC removal rate reached62.4%,82.4%and84.1%, respectively, for in N2, Air, O2gas bubbling conditions, the mineralization is affected by the initial concentration of CIP, initial pH, H2O2dosage, Fe2+dosage.4) The TiO2introduced in MW/UV system forming MW/UV/TiO2process, which is also can degrade CIP efficiently, in100mg/L CIP, pH=3, aeration rate0.6L/min, the TiO2dosage2g/L, reaction time120min, the degradation rate in N2, Air, O2were21.4%,99.3%and99.5%, respectively; the degradation followed the pseudo first order reaction kinetics, the rate constants were0.0032min-1(N2),0.0780min-1(Air),0.0976min-1(O2), respectively; the TOC removal were13.2%,62.4%, and82.7%, respectively; the effect of initial solution concentration, initial pH of solution, amount of aeration, the dosage of TiO2on the degradation of CIP were studied.5) The oxidation ability of the above four systems was compared, from low to high order:MW/UV<MW/UV/H2O2=MW/UV/TiO2<MW/UV/H2O2/Fe2+, the different mechanisms were discussed in this study.