【作者】 王玉萍；

【导师】 王连军；

【作者基本信息】 南京理工大学 ， 环境工程， 2008， 博士

【摘要】 萘系染料中间体产品包括萘胺类、萘酚类、萘磺酸类、羟基萘磺酸类等,其生产废水往往成分复杂、浓度高、毒性大、色泽深、难以生物降解,酸碱性强,是国内外环保界公认的治理难题。研究开发此类难降解有机污染物经济实用的处理技术对我国的萘系有机中间体生产有着重要的意义。近年来,利用纳米TiO₂半导体粉末作为光催化剂催化降解有机物的研究已成为热点。对TiO₂光催化剂的研究主要集中在两个方面,一是提高催化剂的催化活性尤其是提高催化剂在可见光下的光催化活性;另一方面是研究制备具有大比表面积的负载型光催化剂,解决实际操作过程中的分离和可能产生的二次污染问题。本文以1-萘酚-5-磺酸（又称L-酸）为目标物,利用溶胶-凝胶法制备了S掺杂和Mo掺杂的S/TiO₂、Mo/TiO₂催化剂,探讨了L-酸在紫外和可见光及S/TiO₂作用下的降解机理和降解历程:以粒状活性炭为载体,制备活性炭负载的TiO₂和Mo/TiO₂催化剂,研究了负载型催化剂对几种萘化合物的降解效果。主要的研究结果如下:（1）采用溶胶.凝胶法制备了Mo/TiO₂光催化剂。研究表明:焙烧温度和Mo的掺杂量影响催化剂的光吸收范围、强度以及催化剂中锐钛矿相的含量。实验结果得出:Mo⁶⁺掺杂量在4.5%时,焙烧温度为500℃,样品的吸收带边可达460nm,锐钛矿相的含量最高,催化剂的粒径为20nm左右。由于Mo⁶⁺与Ti⁴⁺的半径相近,Mo⁶⁺进入TiO₂晶格内部后替代Ti⁴⁺发生缺陷和电荷不平衡,产生杂质能级,使催化剂的能级变窄,同时避免了电子与空穴的快速复合,从而扩展了吸收光波长的范围,提高了其光催化活性。比较不同光源下Mo/TiO₂和纯TiO₂催化剂对10 mg·L^-1L-酸的去除率可知,Mo/TiO₂催化剂的紫外光活性和可见光活性均高于未掺杂的TiO₂。（2）采用溶胶.凝胶和浸渍法制备的Mo-TiO₂/AC负载催化剂。Mo掺杂量为4.5%的Mo-TiO₂/AC经过400℃焙烧,活性炭载体上的TiO₂为锐钛矿相,粒径约为17.8nm,TiO₂的负载量为11.69%,BET比表面积为862.7 m²·g^-1。在TiO₂和活性炭的协同作用下,负载催化剂对亚甲蓝的吸附量比载体和纯TiO₂分别增加了11.3%和39.0%。增加负载次数,可以提高活性炭上TiO₂的负载量,但同时使催化剂的比表面积下降,光催化活性下降。Mo-TiO₂/AC负载催化剂对L-酸有较好的可见光活性,在420nm可见光照射下,溶液总有机碳的去除率与有机物的去除率趋势相同。L-酸溶液在可见光下的光催化降解反应基本符合一级动力学规律,L酸的浓度在39.0-135.2mg·L^-1范围内,线性拟合的相关系数为0.9906～0.9969。催化剂反复使用4次,催化活性基本不变。（3）以钛酸丁酯为前驱体,硫脲为硫源,采用溶胶.凝胶法制备S/TiO₂催化剂,其最佳的制备条件为:硫的加入量为18%,催化剂的煅烧温度为500℃。所制备的S/TiO₂催化剂为锐钛矿型,其平均粒径为9.7nm,催化剂中S含量约为1.2%。在S/TiO₂催化剂的晶格内,S取代O,形成Ti-S键,而在催化剂的表面,S是S⁶⁺和S⁴⁺形式形成SO₄^2-和SO₃^2-基团螯合在TiO₂表面。且大部分硫在表层。S/TiO₂的等电点为4.75。由于S的掺入,S_3p态与TiO₂价带的交叉使价带宽度增加,S/TiO₂的带隙能降低到2.76eV,使S/TiO₂催化剂有较好的可见光活性。ESR测试发现S/TiO₂在可见光下主要产生·O₂^-和’OOH自由基,而紫外光下产生·OH、·O₂^-和’OOH的自由基。S/TiO₂催化剂既有较好的可见光催化活性,又保持较高的紫外光活性。在250W的紫外灯照射下,对20 mg·L^-1的L-酸溶液反应5h,S/TiO₂和纯TiO₂的去除率分别为92.6%和89.7%;同样的条件在18W的三基色荧光灯照射下反应5h,两催化剂的去除率分别为72.4%和17.8%;S/TiO₂催化剂在420nm以上可见区对L-酸的光催化活性大于Mo/TiO₂。（4）以钛酸丁酯为前驱体,以粒状活性炭为载体,采用溶胶.凝胶和浸渍烧结法负载型催化剂,加入1.0g聚乙二醇2000,且焙烧温度为450℃制备的TiO₂/AC光催化剂中TiO₂含量为13.99%,TiO₂粒子的平均粒径为12.9 nm,催化剂的BET面积为997.0 m²·g^-1。由于TiO₂和活性炭的协同作用,使负载型催化剂对有机物的吸附能力增强,进而增强了催化剂的光催化活性。实验结果表明:与载体活性炭相比,负载后的催化剂粒子对亚甲蓝的吸附值提高了22.5%。催化剂反复使用6次时,催化剂的活性变化不大。在紫外光下TiO₂/AC光催化剂对2-萘酚、1-萘胺和L-酸有较好的去除效果。溶液为中性时有利于2-萘酚和1-萘胺的降解,而溶液在酸性条件下有利于L-酸的降解。三种化合物的降解反应基本符合拟一级动力学规律,可用Langmuir-Hinshelwood（L-H）模型来描述它们在TiO₂/AC上的光降解过程。三种萘化合物在催化剂和紫外光作用下发生分解,被降解的有机物能够最终分解为CO₂等无机物。（5）利用UV-vis、HPLC、FTIR、HPLC/MS、MS、¹HNMR及SPME/GC/MS和溶液的TOC测定等方法,研究了L-酸在S/TiO₂催化剂和光作用下的降解过程和中间产物,实验结果表明:L-酸可以被逐步降解为无机小分子化合物。L-酸分子中最易被氧化的是C-S键,—SO₃H首先从萘环上断裂,形成硫酸根离子,L酸的萘环被打开,被逐步降解成饱和烷烃以及含碳氧双键,碳碳双键以及羟基等基团的化合物,光降解主要的中间产物是萘醌和羟基萘醌,它们也容易被光催化降解为无机小分子。更多还原

【Abstract】 The naphthalene series dye intermediate includes the naphthylamine,the naphthol,the naphthalenesulfonic acids,the hydroxyl-naphthalenesulfonic acids and so on.The wastewaters containing naphthalene dyestuffs and their intermediates are characterized with component complex,higher concentrations,toxicity,darker color, acidity or alkalinity and toxicity,and are difficult to be degraded under natural environment.Therefore it is very meaningfulness to study and look for the economical and practical technology that is used for processing wastewater of our country’s naphthalene series.The study of using the nano-TiO₂ semiconductor powder as the photocatalyst for degradation organic pollutions in the environment has become the focus.The study on TiO₂ photocatalyst mainly concentrates in two aspects;improvement the catalytic activity of catalyst especially under visible light, and preparation load photocatalyst with big specific surface area to solve separation of catalyst and probable secondary pollutant.Me-doped and S-doped TiO₂ nanoparticles were syntbesized by sol-gel method, the photocatalytic activity of catalysts was evaluated by photodegradation of 1-naphthol-5-sulfonic acid（L-acid）.The photodegradation mechanism and process of L-acid by S/TiO₂ catalyst on the different light sources were investigated.The photocatalyst of TiO₂ and Me⁺⁶ doped TiO₂ were prepared by a sol-gel method and immobilized to granular activated carbon,and,the degeneration of naphthalene compounds was studied by load catalysts.The primary study was listed as following: （1） The Me-doped TiO₂ catalysts were synthesized by sol-gel method.The results showed that the visible-light responding bound and photocatalytic activity of catalyst and anatase content in catalysts were affected by the doping amount and calcination temperature,when calcination temperature was 500℃and Me doping amount was 4.5%,the catalysts of UV-visible absorption band was about 460nm,the average particle diameter of resultant TiO₂ was about 20 nm and the anatase content is highest. The visible-light responding bound was extended and photocatalytic efficiency of catalysts was improved by crystal defect,unbalanced of electric charge and impurity energy level because radius of Mo⁶⁺ is close to it of Ti⁴⁺,and a few of Ti⁴⁺ was substituted after Mo⁶⁺ enters the TiO₂ crystal lattice,and heighten separation ratio of photo-generated electrons and holes.Compared with degradation efficiency of L-acid of 10 mg/L,it was known that the photocatalytic activity under UV light and visible light of Mo/TiO₂ catalyst are higher than that of pure TiO₂.（2） The photocatalyst of Mo⁺⁶ doped TiO₂ was prepared by a sol-gel method and immobilized to granular activated carbon by coating.When calcination temperature was 400℃and Mo doping amount was 4.5%the doped TiO₂ supported on activated carbon was of anatase with the average particle diameter 17.8nm,the TiO₂ capacity in catalysts was 11.69%,specific areas of catalysts was 862.7 m².g^-1.The adsorption valve of catalyst for methylene blue was respectively increased 11.3%and 39.0%than that of carrier and pure TiO₂ in coordination TiO₂ with activated carbon.The TiO₂ loading on activated carbon increased along with loading time,but,BET surface area of Mo-TiO₂/AC and photocatalytic activity of catalyst decreased along with loading time.The removal efficiency tendency of L-acid and TOC of solution were same under the above 420mm visible light illumination.The photocatalytic degradation reaction of L-acid in visible light was basically agreed with first-order reaction kinetics,and correlation coefficient of linear fitting was 0.9906～0.9969 when the concentration of L-acid was in 39.0～135.2mg.L^-1.The catalyst can be reused for 4 times to keep the degradation efficiency hardly changed.（3） S-doped TiO₂ nanoparticles were synthesized by sol-gel method with tetrabutyl titanate and thiourea as precursor.The best preparation condition was S adding 18% and calcinations temperature 500℃.The average particle size of the s/TiO₂ was about 9.7 nm and its crystal form was anatase and S content in the catalyst was about 1.2%.S substitutes for O to form the Ti-S bond in the S/TiO₂ catalyst crystal lattice while S exists as S⁴⁺ and S⁶⁺ to form SO₄^2-and SO₃^2- and chelate in TiO₂ surface on the surface of crystal lattice,and,the most of S was in surface.The isoelectric point of S/TiO₂ catalyst was 4.75.The s/TiO₂ catalyst have the good visible light activeness because overlap S_3p with the TiO₂ valence band made the valence band width to increase,and the S/TiO₂ band gap can reduce to 2.76eV.It was found by electron spin resonance spectrum test that S/TiO₂ system can produce·O₂^-and ’OOH radicals in visible light and·OH,·O₂^-and ’OOH radicals in UV light.The photocatalytic activity of S/TiO₂ catalyst for the photodegradation of L-acid in visible and UV light were better than that of pure TiO₂.The photodegradation efficiency of 20 mg.L^-1 L-acid for S/TiO₂ and TiO₂ catalysts and 250W high pressure mercury lamp irradiation 5h was respectively 92.6%and 89.7%.The photodegradation efficiency of 20mg/L L-acid for two catalysts and 20W fluorescent lamp irradiation 5h was respectively 72.4%and 17.8%.The experiment results showed that the photocatalytic activity for L-acid of S/TiO₂ catalyst under visible light above 420nm was greater than that of Mo/TiO₂.（4） TiO₂/AC catalyst was synthesized by sol-gel and soak and sintering method with tetrabutyl titanate and activated carbon as carder.The aggregation of nano-TiO₂ particles can be effectively suppressed by added Polyethylene glycol（PEG） as surface modifier.The results showed that 1.0g of PEG2000,being calcined at 450℃,the average particle diameter of resultant TiO₂ was about 12.9nm and TiO₂ loading was 13.99%and its crystal form was anatase,BET surface area was 997.0 m².g^-1.As a result of TiO₂ and the activated carbon synergism,adsorption valves of TiO₂/AC photocatalyst increased 22.5%as that of the active carbon for methylene blue.The catalyst can be reused for 4 times to keep the degradation efficiency hardly changed.2-naphthol,1-naphthylamine and L-acid can be degraded for inorganic compound with TiO₂/AC catalyst and UV light irradiation.The solution being neutrality was advantageous for degradation of 2-naphthol and 1-naphthylamine, while it was acidity for degradation of L-acid.The photocatalytic degradation reaction of three compounds in UV light and TiO₂/AC catalyst was basically agreed with first-order reaction kinetics,and followed basically Langmuir-Hinshelwood dynamic mechanism.（5） The degeneration process and the intermediary product of L-acid under the S/TiO₂ catalyst and the visible and UV light were studied by UV-vis,HPLC,FTIR, HPLC/MS,MS,¹HNMR,SPME/GC/MS and TOC techniques.The results showed that L-acid could be degraded gradually to inorganic small molecular compound. The C-S bound in L-acid was oxidized easily,-SO₃H group was first broken from the naphthalene ring and formed the sulfate,and the naphthalene ring was broken and was degraded gradually to saturated alkane and compounds which contained the carbon-oxygen double bond,carbon-carbon double bond and hydroxyl.The main intermediary product of photodegradation of L-acid was naphthaquinone and the 5-hydroxy naphthaquinone that were easily degraded for inorganic compounds by S/TiO₂ catalyst.更多还原