Ag–AgBr/TiO2/RGO nanocomposite: Synthesis, characterization, photocatalytic activity and aggregation evaluation

Ag–AgBr/TiO_2 supported on reduced graphene oxide(Ag–AgBr/TiO_2/RGO) with different mass ratios of grapheme oxide(GO) to TiO_2 were synthesized via a facile solvothermal-photo reduction method. Compared to the single-, two-and three-component nanocomposites,the four-component nanocomposite, Ag–AgBr/TiO_2/RGO-1 with mass ratio of GO to TiO_2at 1%, exhibited a much higher photocatalytic activity for the degradation of penicillin G(PG)under white light-emitting diode(LED-W) irradiation. The PG degradation efficiency increased with the increase of mass ratio of GO to TiO_2 from 0.2% to 1%, then it decreased with the increase of mass ratio of GO to TiO_2 from 1% to 5%. The zeta potentials of RGO-nanocomposites became more negative with the presence of humic acid(HA) due to the negatively charged HA adsorption, resulting in the shift of points of zero charge to lower values of pH. The aggregations of nanocomposites were more significant due to the bridging effect of HA. Furthermore, the aggregated particle sizes were larger for RGO-nanocomposites compared to other nanoparticles, due to the bindings of the carboxylic and phenolic functional groups in HA with the oxygen-containing functional groups in the RGO-nanocomposites.The microfiltration(MF) membrane was effective for the nanocomposites separation. In the continuous flow through submerged membrane photoreactor(sMPR) system, backwashing operation could efficiently reduce membrane fouling and recover TiO_2, and thus indirectly facilitate the PG removal.     

钛基石墨烯复合材料的制备及其光催化还原Cr（VI）的研究

通过改进的Hummers法制备氧化石墨烯(GO),再将氧化石墨烯和钛酸四丁酯作为初始反应物,利用溶剂热法制备Ti O_2/RGO纳米复合材料.利用SEM、TEM、XPS、XRD等分析手段对Ti O_2/RGO纳米复合材料进行表征,考察其在可见光照射条件下光催化还原水中Cr(Ⅵ)的效能,并对光催化还原机制进行了初步探讨.结果表明,Ti O_2/RGO复合材料的光催化还原能力与单一Ti O_2(P25)相比有了显著提高;复合材料中RGO含量、溶液p H值、催化剂投加量、Cr(Ⅵ)初始浓度均对光催化还原过程有所影响,当复合材料中RGO含量比例为2%、溶液p H值为2,催化剂投加量为40 mg时,光催化还原Cr(Ⅵ)的效率可达98%.光催化还原Cr(Ⅵ)的过程是吸附过程和光催化还原过程的共同作用结果,RGO不但提高了复合材料的吸附能力,还作为复合材料的电子导体,抑制了光生电子-空穴对的复合,增强了复合材料的光催化性能.经过5次循环使用后,复合材料的光催化还原效率仍然保持在90%左右.     

Simulated-sunlight-activated photocatalysis of Methylene Blue using cerium-doped SiO2/TiO2 nanostructured fibers

Cerium-doped SiO₂/TiO₂ nanostructured fibers were fabricated by electrospinning technology. The prepared fibers were characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Using the fibers as catalysts, photocatalytic degradation of Methylene Blue (MB) aqueous solution was carried out under simulated sunlight. The 0.2% Ce doping proved to be the optimal concentration for the doping of TiO₂/SiO₂, compared to other Ce-doped molar concentrations. The 0.2% Ce-doped SiO₂/TiO₂ fibers exhibited higher photocatalytic activity than industrial Degussa P25 and the samples doped with only Ce or SiO₂. The reasons for improving the photocatalytic activity were also discussed. Several operational parameters were studied, which showed that the photocatalytic efficiency of MB was influenced by parameters such as the initial dye concentration, the initial pH, inorganic anions, and so on. In addition, the influences of an electron acceptor and a radical scavenger suggested that OH was the dominant photooxidant during the photocatalytic process. The reuse evaluation of the fibers indicated that their photocatalytic activity had good stability.     

Fe2O3/TiO2负载膨胀珍珠岩光催化降解罗丹明B

为获得高效催化活性的光催化材料,研究不同煅烧氛围对材料在可见光下催化性能的影响,以膨胀珍珠岩（EP）为载体,采用溶胶-凝胶法,在不同煅烧氛围（O₂和/或NH₃）下制备Fe₂O₃/TiO₂负载EP的光催化复合材料〔Fe₂O₃-TEP（O₂）、Fe₂O₃-TEP（NH₃）、Fe₂O₃-TEP（O₂,NH₃）、Fe₂O₃-TEP（NH₃,O₂）〕,采用EDS（X-射线色散能谱）、BET（比表面积及孔径分析）、XRD（X射线衍射）、SEM（扫描电子显微镜）、XPS（X射线光电子能谱）等对复合材料进行表征,并研究了其在可见光下对罗丹明B的光催化降解效果.结果表明:①复合材料成功负载了Ti、Fe元素,负载的TiO₂以锐钛矿型存在,Fe₂O₃的掺杂增强了TiO₂对可见光的响应能力;②不同的煅烧氛围明显影响复合材料的晶粒尺寸、比表面积和光催化性能,其中,Fe₂O₃-TEP（O₂,NH₃）的光催化性能最好,4 h后罗丹明B降解率达到87.59%,Fe₂O₃-TEP（NH₃,O₂）、Fe₂O₃-TEP（O₂）和Fe₂O₃-TEP（NH₃）4 h后对罗丹明B的降解率则分别为65.02%、62.48%和47.48%;③在试验条件下,复合材料的光催化反应符合一阶反应动力学方程,Fe₂O₃-TEP（O₂,NH₃）、Fe₂O₃-TEP（NH₃,O₂）、Fe₂O₃-TEP（O₂）和Fe₂O₃-TEP（NH₃）相应的降解速率常数分别为0.008 3、0.004 3、0.004 3和0.002 7 min-1.研究显示,通过溶胶-凝胶法所制备的复合材料（Fe₂O₃-TEP）经煅烧后所得矿相均一;Fe₂O₃掺杂TiO₂可形成Ti—O—Fe键,减小TiO₂固有的禁带宽度;复合材料光催化性能也受到煅烧氛围的影响,先O₂后NH₃煅烧条件下所得材料的光催化性能最佳.      

Synergistic effect of N- and F-codoping on the structure and photocatalytic performance of TiO2

Three types of TiO₂ nanostructures were synthesized via a facile hydrolysis method at 195 °C. Effects of the preparation method and doping with N and F on the crystal structure and photocatalytic performance of TiO₂ were investigated. The nanomaterials were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller porosimetry, ultraviolet–visible diffuse reflectance spectroscopy and fluorescent emission spectra. Their photo-catalytic activity was examined by the photodegradation of methylene blue in aqueous solution under both ultra-violet and visible light irradiation. The results show that nitrogen and fluorine co-doped anatase TiO₂ had the characteristics of a smaller crystalline size, broader light absorption spectrum and lower charge recombination than pure TiO₂. Most importantly, more efficient photocatalytic activity under both ultra-violet and visible light was observed. The obtained N–F-TiO₂ nanomaterial shows considerable potential for water treatment under sunlight irradiation.     

BiOCl/TiO2的氯化改性及其新式光生自由基催化反应

采用溶胶凝胶法制备了BiOCl/TiO₂复合催化剂,透射电镜（TEM）照片显示,两种半导体分布均匀、相互连接,形成的异质结可以为电子传导提供有效通道.经过氯化处理的复合材料具备更强的光催化能力,在紫外光条件下对苯的降解率达到90%,是原BiOCl/TiO₂的2倍、纯TiO₂的10倍.本文利用X射线光电子能谱、红外光谱和电子顺磁共振,对表面氯化的机理进行研究.结果表明,氯元素以Ti—Cl的方式吸附在催化剂表面,在光照条件下光生空穴夺取一个电子,使其生成氯自由基,进而配合超氧、羟基,构成一种新型的三自由基光催化体系,使催化降解能力大幅提升.最后,利用实验方法得到了光生氯自由基的直接证据,并构建了该体系的光催化反应机理.     

SiO2纳米颗粒内嵌强化介孔TiO2单晶光催化降解盐酸四环素

吸附性能和光生载流子的分离效率是决定光催化降解抗生素的主要因素.为提高介孔TiO_2单晶(MSCs)的吸附性能和光生载流子的分离效率,在MSCs内部构建SiO_2纳米颗粒吸附结构.同时,利用表面光电压谱、氮气等温吸附-脱附、X射线衍射等研究其结构特性.最后,以盐酸四环素为抗生素代表,通过控制SiO_2纳米颗粒比表面积,考察SiO_2对复合材料吸附及光催化性能的影响.结果表明,SiO_2纳米颗粒与TiO_2单晶复合显著提高了材料的吸附性能,表面保护蚀刻进一步提升了材料的比表面积.实验条件下,高比表面积SiO_2-TiO_2单晶复合材料(KSiO_2@TiO_2)对盐酸四环素的平衡吸附量、降解效率、降解速率常数和矿化率分别达到了0.96 mg·g-1、90.2%、0.0079 min-1、54.4%,分别是MSCs的4.4、1.5、2.6和3.1倍.副产物分析表明,SiO_2复合介孔单晶材料更易将盐酸四环素降解为小分子物质.     

UV/TiO2/H2O2体系对制药废水二级出水的处理特性研究

以某制药企业的二级出水为研究对象,对比了UV/TiO₂、UV/H₂O₂、UV/TiO₂/H₂O₂ 3种高级氧化工艺的处理效果,利用自主设计的一体化光催化装置进行了连续动态试验,并通过凝胶渗透色谱（GPC）、傅里叶变换红外光谱（FT-IR）、三维荧光光谱（EEM）、斑马鱼急性毒性试验等方法研究了处理前后有机物特性和生物毒性的变化.结果表明,与UV/TiO₂和UV/H₂O₂体系相比,UV/TiO₂/H₂O₂光芬顿体系对有机物的去除效果更好,当TiO₂投加量为1 g·L^-1,H₂O₂投加量为100 mg·L^-1时,处理效果达到最佳.一体化光催化装置能够利用UV/TiO₂/H₂O₂光芬顿技术快速高效地降解二级出水中的有机污染物,反应30 min时COD去除率达到50%以上.经UV/TiO₂/H₂O₂深度处理后,废水中的大分子有机物分解转换为小分子,有机物中的不饱和结构明显减少,腐殖质等溶解性有机物基本降解完全.毒性试验结果表明,该二级出水的生物毒性经深度处理后显著降低,对斑马鱼胚胎不存在致畸致死效应.     

Bi掺杂In2TiO5纳米带的制备及其光催化性能

以Bi(NO_3)_3、Ti(OC_4H_9)_4、In(NO_3)_3和聚乙烯吡咯烷酮(PVP-K30)为原料,采用静电纺丝法和沉淀法相结合,成功制备了Bi掺杂In_2TiO_5(Bi-In_2TiO_5)纳米带.利用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线能量色散谱(EDS)、紫外-可见漫反射光谱(UV-vis DRS)和氮气吸附-脱附等温线(BET)等技术对样品进行表征.结果表明,Bi的掺杂未引入新的杂相,样品均为正交晶系结构,掺杂前后样品的形貌未发生明显变化.适量的Bi掺杂,在In2Ti O5晶格中形成杂质能级,降低了In_2TiO_5的带隙能.当掺杂量为2%时,制备的Bi-In_2TiO_5纳米带的光催化活性最高.在氙灯(150 W)辐照下,150 min,对罗丹明B的降解率达95.8%,且该催化剂对氟喹诺酮类抗生素左氧氟沙星(LEV)也表现出优良的光催化降解性能.     

Tricrystalline TiO2 with enhanced photocatalytic activity and durability for removing volatile organic compounds from indoor air

It is important to develop efficient and economic techniques for removing volatile organic compounds(VOCs) in indoor air. Heterogeneous Ti O_2-based semiconductors are a promising technology for achieving this goal. Anatase/brookite/rutile tricrystalline Ti O_2 with mesoporous structure was synthesized by a low-temperature hydrothermal route in the presence of HNO_3.The obtained samples were characterized by X-ray diffraction and N_2 adsorption–desorption isotherm. The photocatalytic activity was evaluated by photocatalytic decomposition of toluene in air under UV light illumination. The results show that tricrystalline Ti O_2 exhibited higher photocatalytic activity and durability toward gaseous toluene than bicrystalline Ti O_2,due to the synergistic effects of high surface area, uniform mesoporous structure and junctions among mixed phases. The tricrystalline Ti O_2 prepared at R HNO_3= 0.8, containing80.7% anatase, 15.6% brookite and 3.7% rutile, exhibited the highest photocatalytic activity,about 3.85-fold higher than that of P25. The high activity did not significantly degrade even after five reuse cycles. In conclusion, it is expected that our study regarding gas-phase degradation of toluene over tricrystalline Ti O_2 will enrich the chemistry of the Ti O_2-based materials as photocatalysts for environmental remediation and stimulate further research interest on this intriguing topic.     

Rubber sheet strewn with TiO2 particles:Photocatalytic activity and recyclability

A new method for the preparation of rubber sheet strewn with titanium dioxide particles (TiO₂-strewn sheet) is presented. This simple and low cost method is based on the use of TiO₂ powder (Degussa P25) being strewn onto the sheet made from rubber latex (60% HA) through a steel sieve. The characteristic of the TiO₂-strewn sheet was studied by using scanning electron microscopy/energy dispersive X-ray spectrometer (SEM/EDS) and X-ray diffractometer (XRD) techniques. The photocatalytic activity of TiO₂-strewn rubber sheet was evaluated using Indigo Carmine (IC) dye as a model for organic dye pollutant in water. The results showed that the TiO₂-strewn sheet could degrade IC dye solution under UV light irradiation. The effects of pH, initial concentration, and the intensity of UV light on the photodegradation were also investigated. Kinetics of the photocatalytic degradation was of the first-order reaction. The used TiO₂-strewn sheet can be recovered and reused. The recycling uses did not require any cleaning between successive uses and no decline in the photodegradation efficiency was observed compared with freshly prepared TiO₂-strewn sheet.     

CuO-TiO2/导电聚合物纤维复合材料的制备及其光催化性能

利用高压静电纺丝技术,制得含羧基的导电聚合物纤维(聚偏氟乙烯/苯乙烯-马来酸酐共聚物/纳米石墨).水热条件下在纤维表面原位合成了纳米级的TiO2,再通过水热法在TiO2表面制备了微米级的球形CuO颗粒,得到CuO-TiO2/导电聚合物纤维复合材料.运用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、紫外-可见吸收光谱仪(UV-Vis)和热失重分析(TGA)对复合材料的结构与性能进行表征,并利用氙灯模拟太阳光进行光催化降解次甲基蓝实验.结果发现,CuO-TiO2/导电聚合物纤维复合材料的降解效率高于CuO-TiO2/非导电聚合物纤维、CuO-TiO2粉体和Degussa P25,光催化降解3.5h时,次甲基蓝的残留率为4.7％.     

In_2TiO_5纳米带的静电纺丝法制备及光催化性能

以酞酸丁酯(Ti(OC_4H_9)_4)、硝酸铟(In(NO3)3)和聚乙烯吡咯烷酮(PVP-K30)为原料,采用静电纺丝技术制备了In_2TiO_5纳米带.利用X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外-可见漫反射光谱(UV-vis DRS)和氮气吸附-脱附等温线(BET)等技术对样品进行了表征.考察了In_2TiO_5纳米带在光催化降解罗丹明B(RhB)、甲基橙(MO)、亚甲基蓝(MB)和左氧氟沙星(LEV)过程中的应用性能,研究了不同离子型物质、溶液的pH和MB起始浓度对In_2TiO_5纳米带光催化活性的影响.结果表明:In_2TiO_5纳米带具有正交晶系结构,禁带宽度为3.47 eV,比表面积为20.71 m~2·g~(-1),可应用于4种不同离子型物质的光催化降解,发现光催化效果与被降解物质的表面带电性质有关.在紫外光照射下,90 min,对MB的降解率达98.1%,其降解过程服从一级动力学模型.     

Tricrystalline TiO2 with enhanced photocatalytic activity and durability for removing volatile organic compounds from indoor air

It is important to develop efficient and economic techniques for removing volatile organic compounds (VOCs) in indoor air. Heterogeneous TiO₂-based semiconductors are a promising technology for achieving this goal. Anatase/brookite/rutile tricrystalline TiO₂ with mesoporous structure was synthesized by a low-temperature hydrothermal route in the presence of HNO₃. The obtained samples were characterized by X-ray diffraction and N₂ adsorption–desorption isotherm. The photocatalytic activity was evaluated by photocatalytic decomposition of toluene in air under UV light illumination. The results show that tricrystalline TiO₂ exhibited higher photocatalytic activity and durability toward gaseous toluene than bicrystalline TiO₂, due to the synergistic effects of high surface area, uniform mesoporous structure and junctions among mixed phases. The tricrystalline TiO₂ prepared at R_HNO3 = 0.8, containing 80.7% anatase, 15.6% brookite and 3.7% rutile, exhibited the highest photocatalytic activity, about 3.85-fold higher than that of P25. The high activity did not significantly degrade even after five reuse cycles. In conclusion, it is expected that our study regarding gas-phase degradation of toluene over tricrystalline TiO₂ will enrich the chemistry of the TiO₂-based materials as photocatalysts for environmental remediation and stimulate further research interest on this intriguing topic.     

Visible light responsive N-F-codoped TiO2 photocatalysts for the degradation of 4-chlorophenol

Visible light responsive N-F-codoped TiO₂ photocatalysts exhibit a higher catalytic activity than N-doped TiO₂ for the degradation of 4-chlorophenol due to the synergistic effect of nonmetal elements.     

WC/TiO2纳米复合界面光催化剂制备及其光催化降解酚类污染物研究

设计并制备了新型WC/TiO2纳米复合界面光催化剂应用于酚类污染物的光催化降解反应中.采用X射线衍射(XRD)和扫描电子显微镜(SEM)技术分析了WC/TiO2纳米复合界面光催化剂的晶型和表面形貌.结果显示锐钛矿型TiO2纳米颗粒均匀地分散在WC纳米球表面并很好地构筑了WC/TiO2界面.研究了不同WC负载比例的WC/TiO2光催化剂在模拟太阳光照射下降解苯酚的光催化性能.结果表明:WC/TiO2复合界面的形成可以有效地提高TiO2光催化降解性能;其中,3%WC/TiO2(质量分数)光催化降解苯酚的活性最高.利用紫外-可见光谱(UV-Vis)和高效液相色谱-质谱联用技术(HPLC-MS)分析了WC/TiO2纳米复合界面光催化剂降解苯酚的中间产物,提出了苯酚在WC/TiO2界面上可能的降解机理.     

FeTiO3/TiO2纳米异质结的制备和可见光催化性能

采用水热法和溶胶凝胶法制备了新型FeTiO3/TiO2纳米异质结复合材料,并明确了最优的掺杂比例(0.5%).随后利用X射线衍射能谱(XRD)、紫外-可见漫反射光谱(UV-Vis DRS)、扫描电镜(SEM)和透射电镜(TEM)等手段对该复合材料进行表征,证实了其结晶度、吸光度随掺杂量的规律性变化.电镜照片显示,该复合材料具有蓬松多孔的微观结构,且晶格条纹清晰、分散度高,有利于光电子的传导.对苯的降解实验表明,相比于纯TiO2,该催化剂的气相可见光催化能力大幅提高,降解率提升了3倍,达到40%,而CO2生成量提升了5倍,超过300 ppm.同时,电化学测试和电子顺磁共振谱(ESR)等均证实,FeTiO3的窄能带能够提高TiO2的光响应,实现可见光激发;而二者的能带相互匹配,有助于转移光生载流子,实现电子-空穴的高效分离,进而其光生电子和自由基生成能力大幅增强,因此,表现出了较强、较稳定的光催化活性.     

RGO/TiO2光催化降解2,4-二氯苯氧乙酸研究

通过Hummers法及紫外光/热还原工艺制得还原氧化石墨烯(RGO),采用溶胶-凝胶-煅烧法,以RGO和钛酸酊脂为前驱体制备出RGO/TiO2光催化复合材料,并利用XRD、FT-IR等对其进行了表征.对RGO/TiO2光催化降解性能的研究发现,复合光催化剂RGO/TiO2对2,4-二氯苯氧乙酸(2,4-D)的光催化降解活性显著优于纯TiO2,并且发现负载量和pH值对光催化降解性能有较大的影响:RGO/TiO2投加量为1.2g·L~(-1)、RGO负载量2%、pH为3、初始浓度为50 mg·L~(-1)反应12 h,2,4-D去除率达到98.75%;2,4-D降解率随着RGO/TiO2投加量的增大先增大后减小;RGO/TiO2对2,4-D的降解为脱氯还原和催化氧化过程,产生氯酚、苯酚等中间产物.     

Surface modification of polypropylene non-woven fibers with TiO2 nanoparticles via layer-by-layer self assembly method: Preparation and photocatalytic activity

Polypropylene (PP) meltblown fibers were coated with titanium dioxide (TiO₂) nanoparticles using layer-by-layer (LbL) deposition technique. The fibers were first modified with 3 layers of poly(4-styrenesulfonic acid) (PSS) and poly(diallyl-dimethylammonium chloride) (PDADMAC) to improve the anchoring of the TiO₂ nanoparticle clusters. PDADMAC, which is positively charged, was then used as counter polyelectrolyte in tandem with anionic TiO₂ nanoparticles to construct TiO₂/PDADMAC bilayer in the LbL fashion. The number of deposited TiO₂/PDADMAC layers was varied from 1 to 7 bilayer, and could be used to adjust TiO₂ loading. The LbL technique showed higher TiO₂ loading efficiency than the impregnation approach. The modified fibers were tested for their photocatalytic activity against a model dye, Methylene Blue (MB). Results showed that the TiO₂ modified fibers exhibited excellent photocatalytic activity efficiency similar to that of TiO₂ powder dispersed in solution. The deposition of TiO₂ 3 bilayer on the PP substrate was sufficient to produce nanocomposite fibers that could bleach the MB solution in less than 4 hr. TiO₂-LbL constructions also preserved TiO₂ adhesion on substrate surface after 1 cycle of photocatalytic test. Successive photocatalytic test showed decline in MB reduction rate with loss of TiO₂ particles from the substrate outer surface. However, even in the third cycle, the TiO₂ modified fibers are still moderately effective as it could remove more than 95% of MB after 8 hr of treatment.     

Fabrication of Bi2O3/TiO2 nanocomposites and their applications to the degradation of pollutants in air and water under visible-light

A nanoheterojunction composite photocatalyst Bi2O3/TiO2working under visible-light(λ 420 nm) was prepared by combining two semiconductors Bi2O3 and TiO2 varying the Bi2O3/TiO2molar ratio. Maleic acid was employed as an organic binder to unite Bi2O3 and TiO2 nanoparticles. The SEM, TEM, XRD and diffuse reflectance spectra were utilized to characterize the prepared Bi2O3/TiO2nanoheterojunction. The nanocomposite exhibited unusual high photocatalytic activity in decomposing 2-propanol in gas phase and phenol in aqueous phase and, evolution of CO2 under visible light irradiation while the end members exhibited low photocatalytic activity. The composite was optimized to 5 mol% Bi2O3/TiO2. The remarkable high photocatalytic efficiency originates from the unique relative energy band position of Bi2O3 and TiO2 as well as the absorption of visible light by Bi2O3.