共查询到20条相似文献，搜索用时 424 毫秒
1.
The influence of calcination temperature on TiO2 nanotubes' catalysis for TiO2/UV/O3 was investigated. TiO2 nanotubes (TNTs) were prepared via the sol-gel method and calcined at 300-700℃, which were labeled as TNTs-300, TNTs-400, TNTs-500, TNTs-600 and TNTs-700, respectively. TNTs were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). It is found that TNTs calcined at 400 ℃ showed the best thermal stability. When the calcination temperature increased from 400 ℃ to 700 ℃, the special structure of tubes was destroyed and gradually converted into nanorods and/or particles. The transformation from anatase to rutile occurred at 600 ℃, and the rutile phase was enhanced when the calcination temperature was increased to over 600 ℃. The calcina-tion temperature's influence on TNTs' adsorption activity for chemical oxygen demand (COD) and catalytic activity for TiO2/UV/O3 was investigated in landfill leachate solution. In landfill leachate solution, the adsorption activity of COD decreased in the reduced order of TNTs-300, TNTs-400, TNTs-500, TNTs-600 and TNTs-700. In photocatalytic ozonation, TNTs-400 showed the best catalytic activity while TNTs-700 exhibited the worst. In other three processes, the COD removal of TNTs-300/UV/O3 was higher than those of TNTs-500/UV/O3 and TNTs-600/UV/O3 in the first 20 min, and then became close to those of the latter two in the following 40 min. Compared with TNTs-300 and TNTs-400, TNTs-600 had the best anti-fouling activity, while TNTs-500 and TNTs-700 had lower anti-fouling activity than the former three. In photocatalytic ozonation, the calcination temperature of 400 ℃ was appropriate when TNTs were obtained at the synthesis temperature of 105 ℃. 相似文献
2.
The crystal form of TiO_2 is a crucial focus of research on the photocatalytic degradation of gaseous pollutants by TiO_2-based composite photocatalysts. To explore the synergistic effect of mixed crystalline TiO_2 on gaseous organic-pollutant photocatalytic degradation, we synthesized a series of TiO_2 nanoparticles with controllable phase ratios. We explored the role of the TiO_2 phase ratio on the photocatalytic activity and degradation pathway in the photodegradation of 2-propanol(IPA). We estimated the crystallite size and crystal proportions of anatase and rutile by X-ray diffraction. We used the Brunauer-Emmett-Teller method to calculate the specific surface area and Fourier transform infrared spectroscopy to characterize the surface chemistry of the samples. Our results show the photocatalytic activities of pure anatase and the sample with 8.6% rutile to be much better than those of the samples with a phase junction and pure rutile. As such, anatase is the better option for the study of photodegradation design and preparation of gas-phase organic pollutants. 相似文献
3.
The influence of calcination temperature on TiO2 nanotubes＇ catalysis for TiO2/UV/03 was investigated. TiO2 nanotubes （TNTs） were prepared via the sol-gel method and calcined at 300--700 ℃, which were labeled as TNTs-300, TNTs-400, TNTs-500, TNTs-600 and TNTs-700, respectively. TNTs were characterized by transmission electron microscopy （TEM） and X-ray diffraction （XRD）. It is found that TNTs calcined at 400 ℃ showed the best thermal stability. When the calcination temperature increased from 400 ℃ to 700 ℃, the special structure of tubes was destroyed and gradually converted into nanorods and/or particles. The transformation from anatase to rutile occurred at 600 ℃, and the rutile phase was enhanced when the calcination temperature was increased to over 600 ℃. The calcina- tion temperature＇s influence on TNTs＇ adsorption activity for for TiO2/UV/O3 was investigated in landfill leachate solution chemical oxygen demand （COD） and catalytic activity In landfill leachate solution, the adsorption activity of COD decreased in the reduced order of TNTs-300, TNTs-400, TNTs-500, TNTs-600 and TNTs-700. In photocatalytic ozonation, TNTs-400 showed the best catalytic activity while TNTs-700 exhibited the worst. In other three processes, the COD removal of TNTs-300/UV/O3 was higher than those of TNTs-500/UV/O3 and TNTs-600/UV/O3 in the first 20 rain, and then became close to those of the latter two in the following 40 rain. Compared with TNTs-300 and TNTs- 400, TNTs-600 had the best anti-fouling activity, while TNTs-500 and TNTs-700 had lower anti-fouling activity than the former three. In photocatalytic ozonation, the calcination temperature of 400 ℃ was appropriate when TNTs were obtained at the synthesis temperature of 105 ℃. 相似文献
4.
《天津大学学报(英文版)》2016,(5)
TiO_2 nanoparticles(NPs)were prepared via the hydrothermal route of TiO_2 xerogel in nitric acid, hydrochloric acid and acetic acid. The physico-chemical properties of the powders were characterized by X-ray diffraction(XRD)and N_2 adsorption desorption techniques. The effects of the different acids on the structure(crystal phase)and texture(primary particle size and porosity)of the TiO_2 powders were explored. Results indicated that acetic acid facilitated the formation and stability of pure anatase phase. On the other hand, nitric acid and hydrochloric acid led to the transformation from anatase to rutile. The catalyst synthesized via the hydrothermal route of TiO_2 xerogel in the low concentration hydrochloric acid solution(Ti-HCl-0.15)had the highest photocatalytic activity than the catalysts obtained in the other two acid solutions. The effects of the different acids were discussed in terms of acid strength, chelating effect and the thermal stability of the adsorbed acidic anions. 相似文献
5.
用XRD,XPS,CO-TPD,NH3-TPD,SO2-TPD和IR等方法表征了SnO2-TiO2固溶体催化剂的物理化学性质,不同配比的SnO2和TiO2均可形成均一的具有金红石结构的连续固溶体,TiO2表面没有酸性,SnO2和SnO2-TiO2呈微弱酸性,经CO还原的SnO2-TiO2上存在大量的强碱中心,说明SnO2和TiO2之间发生了协同作用.SnO2-TiO2固溶体的这些物化性质均十分有利于SO2+NO+CO的氧化还原反应. 相似文献
6.
研究不同氮源、盐度、温度、光照、pH值条件下一株沼泽红假单胞菌的生长情况。结果表明,①作为培养基氮源,氯化铵要比硫酸铵更适宜该菌生长;②在8‰～32‰盐度范围内,该光合细菌生长最适的盐度为8‰,8～16‰是该光合细菌生长较为适合的盐度;③在22～34℃温度范围,最适的温度是31℃;④该光合细菌在室外日光下（60 000lx,26～38℃）下生长稍快于室内阴凉处,但变化并不是很大;⑤在pH 4.5,5,5.5和6的酸碱范围内,pH 6最适宜该光合细菌生长。环境条件对该光合细菌的生长有重要影响。 相似文献
7.
《天津大学学报(英文版)》2016,(3)
An efficient visible-light-responsive BiOBr/TiO_2 heterojunction nanocomposite was fabricated successfully using in-situ depositing technique at room temperature by introducing Bi OBr onto the surface of TiO_2 nanobelts pre-prepared by hydrothermal reaction and etched with H_2SO_4. The obtained particles were characterized by XRD, SEM, TEM, XPS, UV-Vis DRS and PL techniques. BiOBr/TiO_2 heterojunction nanocomposites with different mass ratios of m(Bi OBr)/m(TiO_2) were discussed in order to get the best photocatalytic activity, and BiOBr/TiO_2-1.0 was proved to be the optimal mass ratio. BiOBr/TiO_2-1.0 exhibited excellent photocatalytic activity in the degradation of Rh B compared with TiO_2 nanobelts, pure Bi OBr and the mechanical mixture of TiO_2 nanobelts and Bi OBr. At last, a possible mechanism of photocatalytic enhancement was proposed. 相似文献
8.
以钛酸丁酯为前躯体,采用溶胶-凝胶法制备TiO2粉体,并通过TEM和XRD分析方法对其结构性能进行表征.检测结果表明:TiO2粉体由5-10nm的球形颗粒组成,晶型为锐钛矿型.通过在不同光源下催化降解水杨酸溶液,对其光催化活性及影响因素进行了分析.实验结果表明:紫外光下此TiO2纳米粉体的光催化活性较高. 相似文献
9.
The crystal form of TiO2 is a crucial focus of research on the photocatalytic degradation of gaseous pollutants by TiO2-based composite photocatalysts. To explore the synergistic effect of mixed crystalline TiO2 on gaseous organic-pollutant photocatalytic degradation, we synthesized a series of TiO2 nanoparticles with controllable phase ratios. We explored the role of the TiO2 phase ratio on the photocatalytic activity and degradation pathway in the photodegradation of 2-propanol (IPA). We estimated the crystallite size and crystal proportions of anatase and rutile by X-ray diffraction. We used the Brunauer–Emmett–Teller method to calculate the specific surface area and Fourier transform infrared spectroscopy to characterize the surface chemistry of the samples. Our results show the photocatalytic activities of pure anatase and the sample with 8.6% rutile to be much better than those of the samples with a phase junction and pure rutile. As such, anatase is the better option for the study of photodegradation design and preparation of gas-phase organic pollutants. 相似文献
10.
PEG/(NH4)2SO4两水相萃取海带多糖的研究 总被引：1，自引：0，他引：1
以海带汁为原料,采用PEG/(NH4)2SO4两水相系统萃取海带汁中的多糖,通过正交实验,确定了多糖萃取的最佳操作条件:当PEG浓度为20%(、NH4)2SO4浓度为19%、pH为3.0、海带汁体积为0.6 mL时,其萃取率为77.8%,当pH为7.5、(NH4)2SO4浓度为1.5 mol/mL时,其反萃率为69.8%. 相似文献
11.
以自制的固体超强酸SO4^2-／TiO2-La^3 作催化剂，通过微波辐射加热合成了苯甲酸乙酯,结果表明，该方法比用硫酸催化法的酯化率高，酯产率达85％．反应条件：苯甲酸0．1mol，乙醇0．3mol，固体超强酸SO4^2-／TiO2-La^3 0．8g，微波辐射功率200W，间歇辐射时间8min。 相似文献
12.
TS-1/SiO_2 extrudate was post-treated with mixed solution of tetrapropyl ammonium hydroxide(TPAOH)and various ammonium salts solution(NH_4F,(NH_4)_3PO_4,(NH_4)_2CO_3,(NH_4)_2SO_4,NH_4CH_3CO_2,NH_4NO_3,NH_4Cl and(NH_4)_2TiF_6).The obtained hierarchical TS-1 catalysts were characterized by many techniques and tested for propylene epoxidation using hydrogen peroxide as an oxidant in a fixed-bed reactor.It was shown that the physicochemical and catalytic properties of the treated TS-1/SiO_2 extrudate depended on the types of ammonium salts added.Compared to the treatment with TPAOH alone,the treatment with a mixed solution of TPAOH and some ammonium salts can greatly improve the catalytic properties of the treated TS-1/SiO_2 extrudate.Some of these ammonium salts were favorable for the incorporation of titanium in the framework,and the beneficial effect depended on the types of ammonium salt.TS-1/SiO_2 extrudate treated with a mixed solution of TPAOH and(NH_4)_3PO_4 exhibited the highest catalyst stability in propylene epoxidation.Such catalytic property can be correlated to high crystallinity,more framework titanium,large specific surface area and large external surface area. 相似文献
13.
以硝酸锂和硝酸锰为原料,尿素为燃料,用液相燃烧合成方法制备尖晶石型LiMn2O4物质,考察了焙烧温度(300-800℃)和焙烧时间(0-48h)对产物的组成结构和晶粒大小的影响.实验结果表明,未焙烧产物中主晶相为LiMn2O4,但含有大量Mn2O3;在300-800℃焙烧时,温度越高,所得尖晶石型LiMn2O4的纯度越高、晶粒越大、晶粒发育越完整,焙烧温度≤600℃时焙烧时间对提高产物中LiMn2O4的纯度影响不大,产物颗粒为纳米级,但焙烧温度大于700℃时影响较大,产物颗粒增大,产物中Mn2O3的含量随焙烧时间增加减少的幅度较大,制备LiMn2O4燃烧产物的最佳焙烧温度为800℃,保温6h左右.但焙烧温度为800℃焙烧时间大于8h时,LiMn2O4会分解生成Mn3O4. 相似文献
14.
采用溶胶-凝胶法,以硝酸铜、二氯化锡和钛酸四丁酯为原料,加入十六烷基三甲基溴化铵(CTAB)作软模板,制备CuO/SnO2/TiO2纳米复合物。分别用SEM、XRD、IR、UV-vis等对产物进行表征分析,CuO/SnO2/TiO2晶粒由锐钛矿相的TiO2、金红石相的SnO2和单斜晶系的CuO组成。以甲基橙为模拟污染物,研究其催化活性,结果表明CuO/SnO2/TiO2纳米复合物具有较好的光催化活性。 相似文献
15.
光催化剂BiVO4的制备、表征及其光催化性能的研究 总被引：1，自引：0，他引：1
采用化学沉淀法制备光催化剂BiVO4,用紫外-可见光谱、X射线衍射对其进行表征。通过光催化还原铬离子和光催化氧化甲基橙的效率来评价该催化剂的活性。实验研究了不同的焙烧温度和不同的焙烧时间对光催化剂BiVO4催化活性的影响。结果表明,制备光催化剂BiVO4的最佳条件是在600度下恒温3h。光催化剂BiVO4在可见光和紫外光的照射下均有较好的光催化还原活性和光催化氧化活性。BiVO4从正方晶相向单斜晶相转化的最佳温度是600°C。焙烧过的BiVO4的紫外-可见吸收光谱较未焙烧的有较大程度的红移,提高了对光的利用率。实验同时还探讨了影响BiVO的光催化活性的机理。 相似文献
16.
采用溶胶-凝胶法制备了膨胀石墨负载TiO2和负载氮掺杂TiO2（N-TiO2）光催化剂,用XRD和SEM对样品进行表征,并以甲基橙溶液为目标降解物进行光催化性能的评价。结果表明：纳米TiO2可牢固地负载在膨胀石墨表面和层间,当达到吸附平衡后,煅烧温度为500℃条件下制备的膨胀石墨负载N-TiO2光催化剂在加入量为10 g/L、反应时间60 min的条件下,对初始浓度为15 mg/L的甲基橙溶液的降解率达到95.2%。 相似文献
17.
TiO2 nanoparticles(NPs)were prepared via the hydrothermal route of TiO2 xerogel in nitric acid, hydrochloric acid and acetic acid. The physico-chemical properties of the powders were characterized by X-ray diffraction(XRD)and N2 adsorption desorption techniques. The effects of the different acids on the structure(crystal phase)and texture(primary particle size and porosity)of the TiO2 powders were explored. Results indicated that acetic acid facilitated the formation and stability of pure anatase phase. On the other hand, nitric acid and hydrochloric acid led to the transformation from anatase to rutile. The catalyst synthesized via the hydrothermal route of TiO2 xerogel in the low concentration hydrochloric acid solution(Ti-HCl-0.15)had the highest photocatalytic activity than the catalysts obtained in the other two acid solutions. The effects of the different acids were discussed in terms of acid strength, chelating effect and the thermal stability of the adsorbed acidic anions. 相似文献
18.
纳米超强酸SO42-/TiO2催化合成苹果酯-A 总被引：6，自引：2，他引：6
以纳米超强酸SO42-/TiO2为催化剂,通过乙酰乙酸乙酯和乙二醇反应合成了苹果酯,研究了各有关因素对产品收率的影响.实验表明,纳米超强酸SO42-/TiO2是合成苹果酯的良好催化剂,在酯醇物质的量比为1∶2.0,催化剂用量为2.0 g,反应时间1.5 h的条件下,苹果酯的收率可达93.2%. 相似文献
19.
利用常压MOCVD法在Si及Al2O3衬底上制备了TiO2薄膜.研究了沉积温度和退火温度对TiO2薄膜结构和形貌的影响,以及TiO2薄膜的光学性质.研究发现,沉积温度为600℃时,制备的TiO2薄膜结构为锐钛矿相,薄膜质量较高.TiO2薄膜在1 090℃高温退火后,薄膜结构完全转变为金红相.TiO2薄膜在可见区域有着高达90%以上透射率,在紫外区域有着强烈的吸收. 相似文献
20.
通过砂培实验探讨了Ca(H2PO4)2、NH4HCO3、(NH2)2CO对氯磺隆降解的影响．实验中用直接气相色谱检测氯磺隆．结果表明：Ca(H2PO4)2的加入使砂样呈酸性，促进氯磺隆的降解，降解曲线遵从抛物线方程；而NH4HCO3的加入使砂样呈碱性，阻碍氯磺隆的降解，降解曲线同样遵从抛物线方程．砂样添加尿素后，氯磺隆高浓度组中氯磺隆的降解曲线遵从抛物线方程，半衰期为30．5天；氯磺隆低浓度组中氯磺隆降解曲线先迅速下降，然后上升，在20天左右出现一顶峰，最后缓慢下降．理论分析认为，这是因为氯磺隆与尿素先形成结合态形式，使可测定氯磺隆浓度迅速下降，然后在微生物等原因的作用下又逐渐破坏其结合，使氯磺隆又释放出来；高浓度组形成的结合态浓度相对较低，不足以显现下凹趋势，只表现出降解曲线平缓．尿素与氯磺隆形成结合态，可能对后茬作物造成危害，应引起高度重视． 相似文献