【正文】 y Semiconductors，Elect rochemical Acta，1993，38 (1)：5660[47] Matthews R，Hydroxylation Reaction Induced by Nearultraviolet Photalysis of Aoueous Titanium Dioxide Suspensions，J Chem Soc Faraday Trans，1998，80：457471[48] Matthews R. Kinetics of Photocatalytic Oxidation of Organic Solutes Over Titanium Dioxide J of Catalysis,1998 (3)：264272外文資料Photosynthesis and Characterization of Pt,Fe and Ag Modified TiO2,2, *1Department of Atomic Science,NationalT sing Hua University,Hsinchu 300,Taiwan,2Chemical Analysis Division,Institute of Nuclear Energy Research, 319,Longtan 325,Taiwan,China.*Email ctyuAbstract: Metal ions modified TiO2 posites were prepared by first embedding nanosized TiO2 particles on the surface of porous ceramic powders,then photocatalytically reducing Fe+,Ag+ and Pt4+ on TiO2 respectively under UV reduced metals were then treated by calcinations at 450℃.The BrunauerEmmettTeller(BET), Scanning Electron Microscopy(SEM),Transmission Electron Microscopy(TEM),Xray diffraction(XRD),and Inductively Coupled PlasmaAtomicEmission Spectrometry(ICPAES) were used to characterize the posites’structure photocatalytic activity under UV irradiation was evaluated by the deposition ofmethylene blue(MB)aqueous solution.Keywords: TiO2,modified,photocatalyst,methylene blue1. IntroductionApplication of heterogeneous photocatalytic reactions with TiO2 for environmental cleanup hasn been widely reported and has bee promising[13] because of its various merits,low cost,chemical stability and ,the drawbacks for TiO2 photocatalysis in wastewater treatment include the difficulty in removing nanosized catalyst from the treated water and the rapid electronhole pair rebination in TiO2 resulting in low quantum yield. Because of the very small particle size requirement for TiO2 catalysts,the use and recollection of it in environmental applications may cause serious ,immobilizing nanosize TiO2 particles on a porous substrate material,such as silica or ceramic powders is of great interest[4，5].To improve the low quantum yields of photocatalytic processes,attempts have been made to deposit transition or noble metals such as Pd,Pt,Rh,Au,and Ag onto the TiO2 surface to increase the charge separation efficiency and inhibit electron and hole rebination induced by photons[68].In this study,the photosynthesis of Fe,Ag and Pt on TiO2/ceramic posite materials using a photocatalytic reduction method is metal modified TiO2 posites were prepared by first embedding nanosized TiO2 particles onto the surface of porous ceramic powders using the hydrolysis Fe3+,Ag+and Pt4+ on the TiO2 surface were photocatalytically reduced under UV reduced metals were then treated by calcination at 450℃.The BET,SEM,TEM,XRD,and ICPAES were used to characterize the posite structure and photocatalytic activity under UV irradiation was evaluated using MB solution deposition.2. ExperimentalTo pare the photocatalytic properties of these posites,4 samples were prepared on ceramic substrates:(A)TiO2ceramic,(B)FeTiO2ceramic, (C)Ag TiO2ceramic,and(D)Pt TiO2ceramic. Sample preparation and characterizationTiCl4,citric acid,HCl,ceramic,and MB reagent grade chemicals were purchased from Merck was slowly dropped into a citric acid/1 M HCl solution in an ice powder was then added into the solution and stirred for 2 solution was dried,and the residue calcined at 450℃to obtain the TiO2/ceramic posite sample.Three grams of H2PtCl6他們的愛(ài)是我前進(jìn)的強(qiáng)大動(dòng)力。感謝我的室友張二剛、郝東偉、尹衛(wèi)國(guó)、霍達(dá)和邊文清對(duì)我生活和學(xué)習(xí)上的關(guān)心和幫助，我會(huì)永遠(yuǎn)懷念和他們一起度過(guò)的這快樂(lè)的四年時(shí)光。在我即將走向工作崗位的時(shí)候，我要感謝呂老師對(duì)我的培養(yǎng)教育，在此表示最誠(chéng)摯的敬意。首先，我要感謝我的指導(dǎo)老師呂燕老師，從論文選題、實(shí)驗(yàn)方案設(shè)計(jì)、數(shù)據(jù)分析到論文撰寫(xiě)及修改老師都給予了全面、細(xì)致的指導(dǎo)。（3）所制得的AgTiO2光催化活性明顯高于未負(fù)載銀的TiO2。得到以下結(jié)論：（1）通過(guò)光催化還原法可以制得具有較高活性的、負(fù)載有貴金屬銀的光催化劑AgTiO2。通過(guò)恒溫鼓風(fēng)干燥的方法制備了TiO2干凝膠，然后通過(guò)熱處理制備了TiO2粉體。 圖34 AgTiO2與TiO2光催化活性比較 從圖34中可以看出，AgTiO2的光催化活性明顯高于TiO2。有關(guān)方面的問(wèn)題還有待進(jìn)一步的研究。 圖33 反應(yīng)次數(shù)對(duì)AgTiO2催化活性的影響 從圖中可以看出,第二次吸光度明顯高于第1次吸光度,而第第4次吸光度較第2次的雖仍有所增加,但變化量非常小,基本上趨于一定值。 反應(yīng)次數(shù)對(duì)AgTiO2光催化活性的影響 該部分實(shí)驗(yàn)所采用的AgTiO2是AgNO3溶液與Na2CO3溶液按2:1的體積比,AgNO3溶液用量為7mL制得的。圖32 Na2CO3與AgNO3溶液體積比對(duì)AgTiO2催化活性的影響 從圖中可以看出,當(dāng)AgNO3溶液溶液與Na2CO3溶液的比例為2∶1時(shí),所制得的AgTiO2光催化活性最高,隨著二者比例的增大, AgTiO2光催化活性逐漸降低。即當(dāng)硝酸銀溶液用量大于7mL后,隨硝酸銀溶液用量的增加,AgNO3溶液的催化活性有比較顯著的下降。 當(dāng)硝酸銀用量由3mL逐漸增加到7mL時(shí),銀的負(fù)載量逐漸增加,金屬銀捕獲電子的作用逐漸增強(qiáng),因而光催化活性逐漸增強(qiáng)；但是,金屬粒子的負(fù)載量也存在一個(gè)最佳值,當(dāng)超過(guò)這個(gè)最佳值,擔(dān)載的金屬量過(guò)大時(shí),金屬上富集的電子過(guò)多,使光誘導(dǎo)產(chǎn)生的空穴與反應(yīng)物的作用處于金屬微粒上的電子與空穴的再?gòu)?fù)合的競(jìng)爭(zhēng)之中。如果能夠減少無(wú)效的電子與空穴的復(fù)合,增大有效光生電子和空穴的數(shù)目,將有利于光催化氧化反應(yīng)的進(jìn)行[45]。,當(dāng)硝酸銀溶液用量小于7mL時(shí), AgTiO2的光催化活性隨AgNO3溶液用量的增加而增強(qiáng)；當(dāng)硝酸銀溶液用量大于7mL時(shí), AgTiO2的光催化活性隨硝酸銀用量的增加而減弱；硝酸銀用量為7mL時(shí)光催化劑的催化活性最高。所制得的各種AgTiO2降解亞甲基藍(lán)溶液的吸光度隨AgNO3溶液用量的變化曲線如圖31所示。（5）取樣結(jié)束后，樣品經(jīng)30min離心分離（轉(zhuǎn)速為3000r/min），取上層清液于664nm下測(cè)定其吸光度值。 （3）混合均勻后，開(kāi)始以2只10W紫外燈為光源進(jìn)行輻照，光源位于溶液正上方17cm處。 AgTiO2光催化活性測(cè)定（1）用量筒量取含量為6mg/L的亞甲基藍(lán)反應(yīng)液500ml于1000ml燒杯中。本研究選用亞甲基藍(lán)為模型化合物,其主要原因是:(1)其分子結(jié)構(gòu)中含有苯環(huán),還含有N、S 雜原子,分子結(jié)構(gòu)具有一定的代表性；(2)工業(yè)上用其與氯化鋅的復(fù)鹽染棉、麻、紙張、皮革,并用于制色淀和墨水等,是一種應(yīng)用廣泛的染料,染料廢水的顏色和毒性對(duì)環(huán)境危害嚴(yán)重,它們的處理是一個(gè)受到廣泛關(guān)注的問(wèn)題；(3)亞甲基藍(lán)對(duì)可見(jiàn)光有明顯的吸收,其吸光度與含量在一定范圍內(nèi)成線性關(guān)系,符合朗伯—比耳定律,含量易于測(cè)定。（3）反應(yīng)一段時(shí)間后加入Na2CO3溶液，所得到的混合液置于2只10W紫外燈下，溶液液面距光源17cm，照射1h，照射同時(shí)用磁力攪拌器攪拌。首先將半導(dǎo)體催化劑浸漬在AgNO3溶液中使部分或全部Ag+吸附在催化劑上，再加入Na2CO3溶液，它與Ag+反應(yīng)生成碳酸銀沉淀，然后用紫外光進(jìn)行輻照，銀被還原并沉積在半導(dǎo)體催化劑表面，所涉及到反應(yīng)的反應(yīng)方程式為：（1）配制AgNO3溶液和Na2CO3溶液,。這是目前制備負(fù)載銀TiO2光催化劑一種比較好的方法[30]。本實(shí)驗(yàn)所用培燒溫度為450℃[43]。隨著溫度的升高，TiO2的晶型由非晶型向銳鈦礦型轉(zhuǎn)變，接著向金紅石型過(guò)度。（7）將凝膠置于恒溫鼓風(fēng)干燥箱中在100℃恒溫下使其干燥，通過(guò)加熱去除凝膠中的水分、有機(jī)基團(tuán)和有機(jī)溶劑，得到黃色晶體。但是強(qiáng)有力的攪拌會(huì)破壞形成凝膠過(guò)程中的網(wǎng)絡(luò)結(jié)構(gòu),延遲凝膠的形成。攪拌速度越快,凝膠時(shí)間越短。試驗(yàn)表明，攪拌對(duì)溶膠凝膠有影響。 （5）測(cè)溶膠pH值，滴加鹽酸，使溶膠體系pH=4。通過(guò)試驗(yàn)發(fā)現(xiàn),向前驅(qū)物的乙醇溶液中加水太快或一次性加入,則鈦酸丁酯的水解速度過(guò)快,水解生成的聚合物來(lái)不及溶于乙醇而直接發(fā)生快速縮聚反應(yīng),試驗(yàn)過(guò)程中會(huì)有大量的塊狀絮凝物生成,得不到穩(wěn)定的透明溶膠。 （4）將滴液漏斗接于四口燒瓶上，將A液倒于滴液漏斗中，控制滴液速度，在強(qiáng)力攪拌的同時(shí)使A液以1滴/秒的速度滴入B液中。 （2）配制B液：分別量取35ml鈦酸丁酯、70ml無(wú)水乙醇、23ml冰乙酸，混合于四口燒瓶中。合成工藝：V鈦酸鹽=35ml，V水=，V總乙醇=105ml（VA乙醇=35ml，VB乙醇=70ml），V冰乙酸=23ml，溶膠體系pH=4,水解溫度26℃[41]?？刂谱茻郎囟?，就可得到不同晶型的TiO2。多鈦酸進(jìn)一步聚合形成膠態(tài)下TiO2，這就是通常所說(shuō)的TiO2溶膠的膠凝過(guò)程。 縮聚反應(yīng)：在溶液內(nèi)，原鈦酸和負(fù)一價(jià)的原鈦酸離子反應(yīng)，生成鈦酸二聚體，此二聚體進(jìn)一步作用生成三聚體、