Polymer-supported titanium dioxide photocatalysts

Material Safety Data SheetTitanium DioxideSection 1: Chemical Product and Company IdentificationProduct Name: Titanium Dioxide CAS#: 13463-67-7TSCA: TSCA 8(b) inventory :Titanium DioxideCI#: Not available. Chemical Formula: TiO2Section 2: Composition and Information on IngredientsComposition:Name CAS # %by WeightTitanium Dioxide 13463-67-7100Toxicological Data on Ingredients: Titanium Dioxide LD50: Not available LC50 :Not availableSection 3: Hazards IdentificationPotential Acute Health Effects: Slightly hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation.Potential Chronic Health Effects:Slightly hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation. CARCINOGENIC EFFECTS:A4 (Not classifiable for human or animal) by ACGIH ,3 (Not classifiable for human) MUTAGENIC EFFECTS: Mutagenic for mammalian somatic cellSection 4: First Aid MeasuresEye Contact: Check for and remove any contact lensesSkin Contact: Wash with soap and water ,Cover the irritated skin with an emollientSerious Skin Contact: Not available.Inhalation: If inhaled , remove to fresh air .If not breathing, give artificial respiration.Serious Inhalation: Not available.Ingestion: Do not induce vomiting unless directed to do so by medical personnel.Serious Ingestion: Not available.Section 5: Fire and Explosion DataFlammability of the Product: Non–flammable.Auto-Ignition Temperature: Not applicableFlash Points: Not applicable.Flammable Limits: Not applicableProducts of Combustion: Not applicableExplosion Hazards in Presence of Various Substances : Risks of the product in presence of mechanical impact :Not available .Risk of the in presence of static discharge ;Not availableExplosion Hazards in Presence of Various Substances:Risks of explosion of the product in presence of mechanical impact: Not available.Risks of explosion of the product in presence of static discharge: Not available.Special Remarks on Fire Hazards: Not combustibleSpecial Remarks on Explosion Hazards: Not available.Section 6: Accidental Release MeasuresSmall Spill:Use appropriate tools to put the spilled solid in a convenient waste disposal container.Large Spill:Use a shovel to put the material into a convenient waste disposal container.Section 7: Handling and StoragePrecautions: Do not breathe dust. Wear suitable protective clothingStorage: Keep container tightly closed .Keep container in a cool ,well-ventilated areaSection 8: Exposure Controls/Personal ProtectionEngineering Controls: Use process enclosures ,local exhaust ventilationPersonal Protection: Safety glasses Lab coat. Dust respirator. Be sure to use an approved/certified respirator or equivalent.GPersonal Protection in Case of a Large Spill: Splash goggles. Full suit. Dust respirator. Boots. Gloves.Section 9: Physical and Chemical PropertiesPhysical state and appearance: Solid. Odor: Odorless.Taste: Tasteless. Molecular Weight: 79.9 g/moleColor: White. pH (1% soln/water): Not availableBoiling Point: 2750°C (4982°C ) Melting Point: 1855°C (3371°F)Critical Temperature: Not available. Specific Gravity: 4.26 (Water = 1)Vapor Pressure: Not applicable. Vapor Density: Not applicable.Volatility: Not available. Odor Threshold: Not available.Water/Oil Dist. Coeff .: Not available. Ionicity (in Water): Not available.Dispersion Properties: Not available.Solubility: Insoluble in cold water ,hydrochloric acid , nitric acid, dilute sulfuric acid ,organic solventsSection 10: Stability and Reactivity DataStability: The product is stable.Conditions of Instability: Not available.Incompatibility with various substances: Reactive with acids.Special Remarks on Reactivity: Reaction of titanium dioxide and lithium occurs around 200°C with a flash of lightSection 11: Toxicological InformationRoutes of Entry: Inhalation .IngestionChronic Effects on Humans: Carcinogenic effects :A4(Not classifiable for human or animal) by ACGIH ,3 (Not classifiable for human)Other Toxic Effects on Humans: Slightly hazardous in case of skin contact (irritant), of ingestion, of inhalation. Special Remarks on Toxicity to Animals: Not available.Special Remarks on Chronic Effects on Humans: Possible carcinogen ( tumorgen ) base on animal data Special Remarks on other Toxic Effects on Humans: Acute Potential Health Effects.Section 12: Ecological InformationProducts of Biodegradation: Possibly hazardous short term degradation products are not likely.Toxicity of the Products of Biodegradation: The products of degradation are more toxic.Section 13: Disposal ConsiderationsWaste Disposal: Waste must be disposed of in accordance with federal ,state and local environment control regulationsSection 14: Transport InformationDOT Classification: Not a DOT controlled material (United States).Identification: Not applicable.Section 15: Other Regulatory InformationAdjusted according with the national standard.Section 16: Other InformationReferences: Not available.。

二氧化钛金红石砂形式英文回答：Titanium dioxide, also known as TiO2, is a widely used compound in various industries. It exists in different forms, one of which is the rutile form, also known as red sand.Rutile is a mineral composed mainly of titanium dioxide and is characterized by its reddish-brown color. It is commonly found in beach sands and is often used as a pigment in paints, coatings, and plastics. The red color of rutile is due to the presence of impurities such as iron oxide.One of the main advantages of using rutile form of titanium dioxide is its high refractive index. This means that it has the ability to scatter and reflect light, making it an excellent choice for applications where high opacity and brightness are desired. For example, in thepaint industry, rutile titanium dioxide is used to provide vibrant and long-lasting colors.Another advantage of rutile titanium dioxide is its excellent UV resistance. It has the ability to absorb and reflect harmful UV rays, making it a popular choice for sunscreen products. The red sand form of titanium dioxide can be used in the production of sunscreens to provide protection against the sun's harmful rays.In addition to its optical properties, rutile titanium dioxide also exhibits good chemical stability and resistance to weathering. This makes it suitable for outdoor applications where durability is important. For example, it is commonly used in the automotive industry for coatings that protect the surface of cars from corrosion and fading due to exposure to sunlight.中文回答：二氧化钛，也被称为TiO2，是一种在各个行业广泛使用的化合物。

当代化工研究Modem Chemical Research35 2021・05基础研究氮掺杂花状黑色二氧化钛(TQ)的制备及光催化性能研究*秦莲郭紫露刘娜马海燕王强段志英(西北民族大学化工学院甘肃730000)摘耍：本论文以金属钛粉和尿素为原料，利用水热法制备出氮掺杂黑色二氧化钛(Ti()2)光催化剂，并对其光催化性能进行了红外光谱、紫外光谱和SEM等表征实验，探讨了氮掺杂花状黑色二氧化钛(Tit)2)光催化剂的光催化性能.将甲基橙溶液作为目标降解染料，在模拟太阳光条件下照射含有不同氮掺杂含量的光催化剂的甲基橙溶液，紫外一可见分光光度计测试不同光催化剂的光催化性能.通过对不同形貌，不同掺杂量的催化剂比较研究，探讨结构与光催化性能之间丝关系.实验结果表明：以尿素:黑色花状二氧化钛=2:1餉比例制备的氮掺杂花状黑色二氧化钛催化剂对甲基橙溶液的催化降解效果最好，提高了对染料的降解作用°关键词：水热法；氮掺杂；花状黑色二氧化钛；可见光催化中图55•类号：0文献标识码：AStudy on Preparation of Nitrogen Doped Flower Black Titanium Dioxide(TiO2)and ItsPhotocatalytic PerformanceQin Lian,Guo Zilu,Liu Na,Ma Haiyan,Wang Qiang,Duan Zhiying(School of Chemical Engineering,Northwest University for Nationalities,Gansu,730000) Abstract:In this paper,the nitrogen-doped black titanium dioxide(RO)photocatalyst was prepared by hydrothermal method using titanium powder and urea as raw materials.The photocatalytic performance of the nitrogen-doped f lower black titanium dioxide(TiO^photocatalyst was studied by infrared spectroscopy,ultraviolet spectroscopy and SEM.Methyl orange solution was used as the target dye for degradation.Methyl orange solution containing different nitrogen doping content was irradiated under simulated sunlight conditions.The photocatalytic performance of different p hotocatalysts was tested by UV-Vis spectrophotometer.The relationship between the structure and p hotocatalytic p erformance was studied by comparing the catalysts with different morphologies and doping amounts.The experimental results showed that the nitrogen-doped f lowery black titanium dioxide catalyst prepared yvith the ratio of u rea to black f lowery titanium dioxide=2:l had the best catalytic degradation effect on methyl orange solution,which improved the degradation effect of d ye.Key words：hydrothermal method^N-doped\floral black titanium dioxide^visible light catalysis随着人类生活方式的改变和工业化的持续发展，如危险响口甸。

Journal of Environmental Scienc es20(2008)1527–1533Inactivated properties of activated carbon-supported TiO2nanoparticles forbacter ia and kinetic studyLI Youji,MA Mingyuan,WANG Xiaohu,WANG XiaohuaCollege of Chemistry and Chem ical Engineering,Jishou University,Hunan416000,China.E-mail:bccly j@Received10December2007;revised16January2008;accepted19February2008Abstr a ctThe activated carbon-supported TiO2nanoparticles(TiO2/AC)were prepared by a properly controlled sol-gel method.The e ects of activated carbons(AC)support on inac tivated properties of TiO2nanoparticles were e valuated by photocatalytic inactivation experiments of Escher ichia coli.The key factors a ec ting the inactivation e ciency were investigated,including electric power of lamp, temperature,and pH values.The results show that the TiO2/AC composite s have high inactivation properties of E.coli in comparison with pure TiO2powder.The kinetics of photocata lytic inactivation of E.coli was found to follow a pseudo-rst order rate law for TiO2/AC composites,and kinetic behavior could be describe d in terms of a modi ed Langmuir-Hinshelwood model.The values of the adsorption equilibrium constants for the bacteria,K c,and for the rate constants,k r,were ce rtainly depended on TiO2content.At47 wt.%TiO2coatings with the highest rate constant,the K c and k r were1.17×108L/cfu and1.43×106cfu/(L min),respectively.The variety of parameters shows signi cant e ects on inactiva tion rate.The outer layer of bacteria decomposed rst resulting in inactivation of cell,a nd with further illum ination,the cells nearly decompose d.Key wor ds:inactivation;activated carbon-supported TiO2;sol-gel method;bacteriaIntroductionDisinfection of water by chlorine or ozone has been carried out for about one hundred years.However,some chlorine residuals in water are toxic to many aquatic organisms,and some byproducts of chlorination in water such as trihalomethane may be carcinogenic.T o avoid adding chemicals to the drinking water,disinfection by photocatalysis with titanium dioxide(T iO2)is generating considerable interest in recent years(Li et al.,1996). There are many publications reporting the application of photocatalysis toward water remediation with recent review articles summarizing the photocatalytic removal of organic,inorganic,and microbial pollutants(Salinaro et al.,1999;Ollis et al.,1991;Heller,1995;Ho mann et al.,1995,Mills and Hunte,1997;Blake et a l.,1999; Fujishima et al.,2000).When TiO2powder is suspended in water and irradiated with near ultraviolet(UV)light belowλ<385nm,electron hole pairs are generated within the metal oxide semiconductor and then are separated between the conductance band and valence band.The valence band hole has a very positive reduction potential and is capable of oxidizing water,or hydroxide ions,to form hydroxyl radicals in water(Mills and Hunte,1997). Hydroxyl radicals are known to be powerful for both the oxidation of organic substances and the inactivation of *yj@63bacteria and virus(Rincon and Pulgarin,2004).Mecha-nisms for the bactericidal action of TiO2photocatalysis have been proposed by a number of authors(Matsunaga et al.,1985;Christensen et al.,2003;Maness et al.,1999; Zheng et al.,2000;Sunada et al.,1998).The results from the above studies suggest that the cell membrane is the primary site of reactive photogenerated oxygen species attack.Oxidative attack of the cell membrane leads to lipid peroxidation.The combination of cell membrane damage and further oxidative attack of internal cellular components ultimately results in cell death.TiO2powder is commonly used in the laboratory in the form of a suspension.This method yields a high catalyst surface area to volume ratio for pollutant hydroxyl radical interaction; however,the catalyst must be removed by a posttreat-ment separation stage,which may not be cost e ective on a large scale.There is an e ective way to remove the need for posttreatment separation that the TiO2is loaded on a high surface area support,such as activated carbon,exfoliated graphite,and optical bers(Hammer and Kvande,2007;Lu et al.,1999;Matsunaga and Okochi, 1995).Meanwhile,this method is not associated with a decrease in surface area to volume ratio and mass transfer resulting in a reduction in the pollutant degradation rate. Matos and coworkers prepared carbon-coated TiO2with high photocatalytic activity and repeated-use property andf()y f qCorresponding author.E-mai l:.investigated in uence o di erent activated carbons A C on the photocatal tic degradation o a ueous organic1528LI Y ouji et al.Vol.20pollutants(Matos et al.,1998,1999,2001).But the studies about bacteria inactivation by T iO2/AC composites and the e ects of AC supports on inactivated properties of composites have not been reported.The main purpose of this article was to evaluate and compare photocatalytic inactivation of T iO2/AC composites and TiO2powder. Meanwhile,W e investigatedthat the e ects of A C supports on inactivated properties of composites from photocatalyt-ic kinetics.Finally,the inactivated mechanism of bacteria was explained in photocatalytic course in term of photo-catalytic characteristics.1Experimental1.1P reparat ion of TiO2/A C compositesCommercially available activated carbon grains from Tianjing,China,which were produced by the vapor ac-tivation of coconut shell,were serially treated and then used.Precursor solutions for TiO2/AC were prepared by the following method.T etrabutylorthotitanate and di-ethanoiamine were dissolved in ethanol.The solution was stirred vigorously for2h at20°C,followed by addition of a mixture of distilled water and ethanol.The resulted alkoxide solution was left at20°C for hydrolysis reaction to produce T iO2sol.Then,a desired amount of activated carbon grains was used as the substrates and was added into T iO2sol with a certain degree.After this,sol changes to gel;TiO2gel coated activated carbon was heat treated at250°C for2h in air and then heating temperature was increased gradually to the end temperature from300to 700°C for2h in a ow of high purity nitrogen using an electric oven.The amount of coated T iO2was adjusted by repeating the cycle from dipping to heat treatment.1.2C ulture of bacter ia and growth mediaEscherichia coli(E.coli,NCIMB8277)was grown under aerobic conditions at37°C overnight in50ml of Luria Bertani(LB)medium(pH7.0)containing tryptone 1%,yeast extract0.5%,and sodium chloride1%.Shaking was done to obtain the necessary oxygen transfer into the medium.The cells were centrifuged at8,000r/min for10 min,washed three times in sterilized Milli-Q water,and resuspended in sterilized water.1.3P hotocatalyt ic reactor operat ionSemiconductor composites or powder was suspended in sterilized water by sonication for5min.As shown in Fig.1,inactivated experiments were carried out in a cylindrical pyrex glass vessel on which there was a black light uorescent lamp to provide the irradiance source. Appropriate dilutions of E.coli suspensions were prepared in photocatalytic systems by E.coli being inoculated in sterilized water.A bacterial suspension without catalysts was irradiated as a control,and a dark reaction was also carried out.Circulation of reactant was provided with a magnetic stirrer.Samples were withdrawn at regularxT j6,,Fig.1Experimental apparatus for photocatalytic reaction.bu er(KH2PO4/NaOH).The resulting phosphate bu er solutions were maintained at approximately20mmol/L. Inactivation temperature was maintained at25,37,and 45°C by a temperature controller.1.4Det er minat ion of viable ba cteriaThe number of viable cells in the solution was deter-mined by plating samples after suitable dilutions on LB medium supplemented with20g/L agar and counting the colonies which appeared after24h of incubation at37°C. Many replicate plates were used and all experiments were repeated more than ve times to obtain a mean value applied in kinetics in terms of statistic principle.All the materials were autoclaved for30min to ensure sterility. 1.5Scanning electron m icroscopyBacteria were deposited on TiO2/AC composites or TiO2powder.The samples were subjected to the stan-dard procedure for sample preparation:after being xed with glutaraldehyde and osmium tetroxide,the samples were drained with ethanol/water in increasing concentra-tions of ethanol.The absolute ethanol was replaced by dimethoxymethane,and the samples underwent critical point drying with CO2.The photocatalysts were glued onto stages and metallized with gold.The samples were microscoped and photographed with a scanning electron microscope(JSM-5600LV,JEOL,Japan).2Results and discussion2.1Cha ract er ization of TiO2/ACThe content of TiO2in composite samples per doped cycle,BET surface area,and total pore volume,including the original A C,are summarized in Table1,together with heat-treatment temperature(HTT)and doped cycle times. Nano-TiO2particles have high surface area to increase surface area of hybridization catalyst by doped surface of AC and at the same time,to decrease surface area by blocking the pore entrances on the surface of AC substrate.For1-doped cycle TiO2/AC,because the former e ect on surface area is stronger than the latter e ect,its surface area is larger than the original AC and increased with increasing heat-treatment temperature.However,for T O y y3y,f yintervals and each e periment was repeated at least twice. he pH was ad usted to7or8using a phosphatei2/AC catal st with2-doped c cles or-doped c cles its sur ace area was decreased markedl and was increasedNo.12Inacti vated properties of activated carbon-supported TiO 2nanoparticles for bacteria and kinetic study1529Table 1Characteristic of TiO 2/AC co mposites and original activated carbon (AC)supportsSample HTT (°C)TiO 2content Doped cycle Surface area T otal poreCrystallite Escherichia coli surviv al (wt.%)(times)(m 2/g)volumn (cm 3/g)phase rate after 100min (%)AC–0–4350.08768Amorphou 92TA1-300300314400.08547Anatase 60TA1-400400414480.08469Anatase 57TA1-500500514560.08231A+R 45TA1-600600914620.08075Ru tile 38TA1-7007001014780.07968Ru tile 32TA2-5005001823730.074874A+R 27TA3-5005004732790.06458A+R 23TA4-5005006342710.05364A+R30HTT:heat-treatment temperature;A+R:anatase and rutile.gradually with increasing heat-treatment temperature,but complete recovery of surface area was not attained.The decrease of surface area is reasonably supposed to be the fact that the e ect of nanometer TiO 2particles on enhancingsurface area were fewer than that of its blocking.The total pore volume of original AC is 0.08768cm 3/g.The total pore volume of TiO 2/AC is smaller than that of original AC and decreases with increasing TiO 2content,which could indicate that T iO 2particles had performance of blocking the pore entrances.Therefore,the change tendency of surface area is the same as that of total pore volume with increasing doped cycle times for catalysts at heat-treatment of 500°C as shown in T able 1.Meanwhile,the ratio of anatase to rutile and TiO 2crystallite phase on TiO 2/AC samples at heat-treatment temperature of 500°C were invariable with changes of T iO 2content.2.2P hotocatalyt ic inactivat ion of E.coliThe time course of viable E.coli cells when cell suspensions (107cfu/ml)were irradiated with powder or composites (2g/L)under lamp light after saturation of adsorption in dark was determined in Fig.2.By the control experiments,the percentage of viable cell counts was observed to be >95%in the absence of photocatalysts.In contrast,the number of viable cells decreased gradually for powder or composites in illumination.After 250min illumination,only 60%–70%of E.coli wereinactivatedF T f f y y L f T O y y ×f using T iO 2powder;however,99.99%of E.coli wereinactivated using TiO 2/AC composites.It is obviously found that the TiO 2/A C composites were more e ective for E.coli inactivation in comparison with powder.The AC e ect on inactivated enhancement as observed in photocatalytic course was mainly due to its high surface area,which shows great adsorbing energy to bacteria,as well as organic molecules more than TiO 2powder.In addition,it is experimentally shown that the carbon in active carbon reduces TiO 2to form more Ti 3+ions (Liu et al.,2003).By acting as active center,the T i 3+can trap photogenerated electrons in the conduction band and prevent the recombination of electron-hole pairs;hence,there are more photogenerated holes in composites.The hole in the valence band received an electron from CoA as the donor to form dimeric CoA.Dimerization of CoA inhibited the respiration and caused the death of the cells (Matsunaga et al.,1988).2CoA –SH +2h +vb →CoA –S –S –CoA +2H +(1)Meanwhile,it can be observed from Fig.2that T iO 2content a ects inactivated properties of composites.The relation between rate of E.coli inactivation and T iO 2content follows the sequence:47%>18%>63%>5%.The survival rate of the E.coli inactivated by the pure T iO 2was nearly 77%after 250min.However,the TiO 2/AC that contained 47%T iO 2has reached almost 100%of the removal of E.coli for 175min.2.3Phot ocat alytic inactivation kinet ics of E.coli byTiO 2/A C com posites The inactivated curves of E.coli by TiO 2/A C are well tted by a mono-exponential curve,suggesting that a pseudo-rst order homogeneous reaction model can be tak-en into consideration for describing the kinetic behavior.However,in photocatalytic inactivation reaction system,the reactant in solution absorbs light and then lowers its intensity,which results in the decrease of photocatalytic activity.So the initial concentration of E.coli has a funda-mental e ect on the degradation rate,i.e.,the kinetic rate constant decreases with the concentration (da Silva and Faria,2003).In other words,from a practical standpoint,at the same illumination time,the relative amount of E.f f T x y T O f f ig.2ime co urse o changes i n the surviv al rate o E.coli caused b photocat al sis wi th 2g/o i 2/AC catal st or without catal sts.E.coli content is 1107c u/ml.coli inactivated is less or the more high content o bacteria solutions.he inactivated e periments b i 2/AC o E.coli ollow the pseudo-rst order kinetics with respect to1530LI Y ouji et al.Vol.20 E.coli concentration(C)in the bulk solution:dCdt=k app C=r(2)Integration of that equation will lead to the expectedrelation:ln(C0C)=k app t(3)where,k app is the apparent pseudo-rst order rate constant and is a ected by E.coli concentration,C0is the initial concentration in the bulk solution after dark adsorption, and t is the reaction time,with the same restriction of C =C0at t=0.Generally,the photocatalytic degradation is assumed to occur on the basis of adsorption,so it can be speculated that the inactivation reaction between the surface-adsorbed substrates and the photogenerated oxidants is predominant, although other pathways may exist(Tunesi and Anderson, 1993).We reasonably postulate that photocatalytic inac-tivation of E.coli on the T iO2supported on porous AC follows a modi ed Langmuir-Hinshelwood model,where the oxidationof intermediates competes with that of E.coli intact cells.Then,the reaction rate can be written as:r=dCdt=k2θHO.θEC t(4)where,k2is a second-order surface rate constant,θHO is the fractional site coverage by HO radicals,andθE C is the fraction of sites covered by E.coli cell(EC)at any time t.Owing to the fact that water is the solvent(i.e.,H2O and OH are in large excess)and the oxygen partial pressure remains the same in a given experiment,the fractional site coverage by HO radicals is also constant,and Eq.(3)can be arranged as:r=dCdt=k rθEC t(5)where,k r is rate constant.k r=k2θHO.includes the second-order rate constant.On the other hand,the fractional site coverage by the E.coli cells is given byθEC=K C C1+K C C+PiK i[I i](6)where,K C and K i are adsorption equilibrium constants, and I refers to the various intermediate products of E. coli decomposition.If it is assumed that the adsorption coe cients for all intermediates present in the reacting mixture are e ectively equal,the following assumption can be made as:K C C+XiK i[I i]=K C C0(7)where,C0is the initial concentration of E.coli.Now, substitution of Eq.(6)into Eq.(5)results on the expression:=×K+K=()The relationship between k app and C0can be expressed asa linear equation:1k app=1k r K C+C0k r(9)The values of k app can be obtained directly from theregression analysis of the linear curve in Eq.(2)(a plot ofln(C0/C)versus t)for all the experiments with di erentinitial bulk concentrations of E.coli.In Fig.3,a plot of1/k app versus C0for di erent T iO2contents of TiO2/A C isshown.The values of K C and k r were obtained by linearregression of the points calculated by Eq.(8).Fig.4showsdependence of k r and K C determined in this way on theTiO2content of TiO2/A C.By comparing the dependenceof the k r on the T iO2content with that of K C given in Fig.4,rate constant rst increases with increasing content ofTiO2,but then decreases;however,absorption equilibriumconstant decrease with increasing content of TiO2.It can beobserved that the rate of E.coli inactivation for TiO2/ACcatalysts is mostly determined by TiO2particles.This maybe caused by the fact that E.coli cells have to be adsorbedinto A C layer and then migrated to the surface of T iO2par-Fig.3Relation between1/k app and C0.F R()fq(K)f f f T Oyr k r C C1C C0k app C8ig.4ate constant k r o E.coli inactivated reaction and theadsorption e uilib rium constant C o E.coli as a unction o the i2content in composite catal st.No.12Inacti vated properties of activated carbon-supported TiO 2nanoparticles for bacteria and kinetic study 1531ticles.The rate of T iO 2/AC catalysts inactivation depends on the content of TiO 2,k r being the lower with the smaller TiO 2content.But absorption strength of substrates is an important factor e ecting photoactivity of catalysts.V ery high adsorption equilibrium constant for 5%TiO 2content of catalyst showed a lowered degradation rate presumably due to low TiO 2content and retardation of easy di usion of the adsorbed E.coli by high absorption strength.The highest rate constant (1.43×106cfu/(L min))was ob-served for the sample,which contained 47%TiO 2with adsorption equilibrium constants of 1.17×108L/cfu.Rate constant appears to increase gradually at a region of TiO 2content below 47%,which is reasonably supposed to be due to increasedamount of T iO 2particles because of the occurrence of photocatalytic inactivation on TiO 2particles.After passing a maximum,rate constant decreases with increasing TiO 2content,which may be due to decreasing amount of adsorbed E.coli drastically decreased (low K C )by reduced surface area.It is obvious that a decrease of the amount of adsorbed substrate resulted in the decrease of the inactivation rate.The inactivation of E.coli through hybrid catalysis process by using TiO 2/AC catalysts is mainly determined by TiO 2particles,but adsorption of E.coli cells into AC layer appears to be also important.This may be due to the photon generated by excitation of TiO 2species can easily contact with E.coli and so the process of their recombination could be avoided,giving high yield of photocatalytic activity.In Fig.3,it can be observed that rate constant k app for 5%TiO 2catalysts with high surface area is higher than that for 63%TiO 2catalysts.However,rate constant k r shows inverse result for both.It can be explained by the fact that degradation of E.coli occurs on TiO 2particles.2.4E ects of electr ic power,temperat ur e,and pH on E.coli inactiva tion To investigate the relation between inactivation rate constant and these parameters including electric power and lamp,temperature,and pH values,a series of experiments was conducted using TiO 2/AC with 47%T iO 2as catalysts.Light intensity is a major factor in photocatalytic reactions because electron-hole pairs are produced by light energy (Ku and Jung,2001).The relation between electric power of the uorescent lamp and its light intensity ts direct ratio when the positions of uorescent lamp and reactor are invariable in Fig.1,so the electric power of the uorescent lamp also in uences photodegradation of bacteria during photocatalytic process.T able 2shows that the rate of inactivation increased with increasing electric power of the lamp.For example,the inactivation constant at 400W was faster than that at 300and 200W.This was because higher electric power provides higher ow of photons,which isavailable not only to directly attack bacteria but also to induce generation of oxidative species on the T iO 2surface that subsequently attack bacteria,increasing considerably the bacterial inactivation rate.In addition,the selfdefense and autorepair mechanisms of bacteria are insu cient to protect cells at high electric power.From T able 2,it can be observed that although most of photoreactions are not sensitive to the small variation in the temperature and very few cases have shown an Arrhenius dependence (Herrman et al.,1993,Eqling and Lin,2001),the modi cations in the initial temperature in these ranges a ect the photocatalytic inactivation of E.coli to a signi cant extent.As the temperature was increased from 25to 45°C,the rate constant of E.coli inactivationwas 1.28×106and 1.63×106cfu/(L min),respectively.This implies that the e ect of temperature on E.coli inactivation in photocatalytic TiO 2disinfection is mainly owing to the change in microorganism susceptibility.The relation between temperature and bacteria inactivation is consistent with description by T ang et a l.(2004).The pH is an important factor in in uencing the pho-tocatalytic process.It was clearly observed that pH 7is an advantage for the photocatalytic inactivation of E.coli (Table 2).The weak acid or alkali is not available for E.coli inactivation,it is owing to the fact that the amount of hydroxy absorption and hydroxy produce on TiO 2is in uenced by pH in solution (Chen et al.,2001).So pH value a ects photocatalytic inactivation process of E.coli because high hydroxy content and plentiful E.coli cells that are absorbed on TiO 2/AC are available for the photocatalytic inactivation.2.5Inactivated m echanism of bacteriaT o elucidate the mechanism for photocatalytic inacti-vation of bacteria cells on T iO 2/AC,the morphology of bacteria cells on TiO 2/AC composites was characterized using SEM with di erent illumination times as indicated in Fig.5.Before illumination,the surfaces of the cells ap-peared grainy,smooth,furrowed,crumbled,or dilapidated (Fig.5a).Even after illumination for 1.0h,no obvious morphological changes were recognized,even though the cells had already lost their viability (Fig.5b).However,the outermost layer that was clearly observed in Fig.5a disappeared after 1.0h of illumination.In contrast,the outermost layer of the cells on TiO 2/AC before illumi-nation remained intact.Therefore,the disappearance of the outermost layer results from the composites photo-catalysis.Furthermore,the observation re ects the change in concentration of the cell wall components and also demonstrates that cells on illuminated T iO 2/AC are decom-posed from the outside of the cell.Along with illumination time,bacteria cells lose the smooth and tight surface.AsT able 2E ects of parameters change on reaction co ns tant k rKinetic constantElectric power of lamp a (W)Temperature b (°C)pH c 200300400253745678×6(f (L ))363636333°;W ;W 3°k r 10c u/min 1.4 1.11.871.281.4 1. 1.2 1.4 1.9aAt 7C and pH 7b at 200and pH 7cat 200and 7 C.1532LI Y ouji et al.Vol.20Fig.5SEM ph otographs of bacteria on TiO2/AC in course of ph otocatalytic inactivation before inactivation(a),inactivation for1.0h(b),and inactiv ation for2.0h(c).shown in Fig.5c,the outer layer of the spherical-shape cells disappeared completely and the inner membrane dissolved after2.0h of illumination,indicating the damage of bacteria cells and starting of decomposition of dead cells.3ConclusionsThe use of A C adsorbents as a support for TiO2is e ec-tive in getting high inactivated rates of bacteria in water phase.These merits are summarized as follows:(1)the adsorbent supports make a high concentration environment of bacteria around the loaded TiO2by adsorption,and then the rate of photocatalytic inactivation is improved;(2)the bacteria are inactivated on the photocatalyst surfaces and then further decomposed.High inactivation e ciency of composite is available to prevent the repair of cells.The amount of T iO2in catalysts may play a signi cant role on the photoe ciency of the hybrid catalysts.The E.coli inactivation process well ts a pseudo-rst order kinetic equation.The photocatalytic inactivation processes can be explained in terms of a modi ed Langmuir-Hinshelwood model for the surface reaction between the bacteria and the oxidizingagent.The values of K C and k r were certainly dependent on the TiO2coatings.At47wt.%T iO2coatings with the highest rate constant,K C and k r was 1.17×108L/cfu and1.43×106cfu/(L min),respectively.The electric power of lamp,pH values,and temperature show signi cant e ects on inactivation rate of E.coli.The scanning electron microscopy measurements of bacteria cells on illuminated T iO2/AC showed that the outer layer decomposed rst resulting in inactivation of cell,and with further illumination,the cells nearly decomposed.These results suggest that the inactivated reaction is initiated by a partial decomposition of the outer wall,followed by dissolving of inner member,and then it resulted in cell death.Acknowledgment sThis work was supported by the Educational and Tech-nological Department of Hunan Province(No.08B063), the Natural Science Foundationof Science and T echnology Department of Hunan Government(No.2007GK3060)D F f U y(N SDXKYZZ6)ReferencesBlake D M,Maness P C,Huang Z,Wolfrum E J,Huang J,Jacoby W A,1999.Application of the photocatalytic 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