Photocatalytic degradation of methylene blue by nanostructured Fe/FeS powder under visible light

The photocatalytic performance of mechano-thermally synthesized Fe/FeS nanostructures formed from micron-sized starting materials was compared with that of a thermally synthesized nanostructure with nano-sized precursors in this paper. The properties of as-synthesized materials were studied by X-ray diffraction（XRD）, transmission electron microscopy（TEM）, vibrating sample magnetometry（VSM）, diffuse reflectance spectroscopy（DRS）, and ultraviolet–visible（UV-Vis） spectroscopy. The effects of irradiation time, methylene blue（MB） concentration, catalyst dosage, and p H value upon the degradation of MB were studied. Magnetic properties of the samples showed that both as-synthesized Fe/FeS photocatalysts are magnetically recoverable, eliminating the need for conventional filtration steps. Degradation of 5 ppm of the MB solution by mechano-thermally synthesized Fe/FeS with a photocatalyst dosage of 1 kg/m^3 at pH 11 can reach 96% after 12 ks irradiation under visible light. The photocatalytic efficiency is higher in alkaline solution. The kinetics of photocatalytic degradation in both samples is controlled by a first-order reaction. However, the rate-constant value in the thermally synthesized Fe/FeS photocatalyst sample is only 1.5 times greater than that of the mechano-thermally synthesized one.

Formation of active radicals and mechanism of photocatalytic degradation of phenol process using eosin sensitized TiO_2 under visible light irradiation

The role of oxygen and the generation of active radicals in the photocatalitic degradation of phenol were investigated using the eosin sensitized TiO2 as photocatalyst under visible light irradiation. Diffuse reflectance spectra show that the absorbancy range of eosin/TiO2 is expanded from 378 nm (TiO2 ) to about 600 nm. The photocatalitic degradation of phenol is almost stopped when the eosin/TiO2 system is saturated with N2 , which indicates the significance of O2 . The addition of NaN 3 (a quencher of single oxygen) causes about a 62% decrease in the phenol degradation. The phenol degradation ratio is dropped from 92% to 75% when the isopropanol (a quencher of hydroxyl radical) is present in the system. The experimental results show that there are singlet oxygen and hydroxyl radical generated in the eosin/TiO2 system under visible light irradiation. The changes of absorbancy indicate that the hydrogen peroxide might be produced. Through the analysis and comparison, it is found that the singlet oxygen is the predominant active radical for the degradation of phenol.

Plasmonic Ag nanoparticles decorated g-C_(3)N_(4)for enhanced visible-light driven photocatalytic degradation and H_(2)production

The plasmonic Ag nanoparticles(NPs)loaded g-C_(3)N_(4)photocatalysts(Ag/C_(3)N_(4))were successfully prepared via a conventional procedure.The fully characterized Ag/C_(3)N_(4)photocatalysts exhibited excellent stability and greatly enhanced visible light-driven photocatalytic performance both in the degradation of methyl orange(MO)and H_(2)evolution from water splitting.The 1.0 wt%Ag/C_(3)N_(4)allowed the highest reaction rate of 0.0294 min^(−1)to be obtained in the MO degradation,which is about 2.3 times higher than the reaction rate of g-C_(3)N_(4)alone of 0.0129 min^(−1).Furthermore,the optimum H_(2)evolution and the k value attained 20μmol and 1.573 h^(−1),respectively,after 12 h of visible light irradiation.The surface plasmon resonance effect of Ag NPs and the charge transfer between the two components of the photocatalyst,strongly promote generation of photoinduced charge carriers while suppressing their recombination.These factors are held responsible for the enhanced visible light photocatalytic performance of Ag/C_(3)N_(4).Our methodology will provide guidance for the design and synthesis of plasmon-enhanced visible light photocatalysts derived from Ag NPs and g-C_(3)N_(4)and their applications in environmental remediation and green energy development.

Evaluation of Reaction Mechanism for Photocatalytic Degradation of Dye with Self-Sensitized TiO₂under Visible Light Irradiation

The dye-sensitized TiO2 method is one of the most promising methods for the visible-light-induced detoxification of pollutants. The reaction mechanism for photocatalytic degradation of orange II (OII) and rhodamine B (RhB) with self-sensitized TiO2 under visible light irradiation (λ > 400 nm) has been evaluated. Radical scavenger studies were carried out to investigate the active species involved in the photodegradation of 5 mg/L of initial concentration of OII and RhB at room temperature. The trapping effects of different scavengers results proved that the oxidation of OII and RhB mainly occurred by the direct oxidization of h+ and ·O2- radicals, while the ·OH radicals played only a relatively minor role in the direct oxidization process.

Strong visible absorption and excellent photocatalytic performance of brown TiO_2 nanoparticles synthesized using one-step low-temperature process

particle size （5.0 nm）, large specific surface area （213.45 m1 2/g）, and efficient response to broadband light over the entire ultraviolet-visible spectrum with a narrow band gap of 1.84 eV. In addition, TiO2 -180℃ exhibited the optimal reaction rate constant for the degradation of methylene blue （0.08287 mg/（Lmin））, which is six times higher than that of the mixed rutile/anatase phase TiO2 photocatalytic standard P25 （0.01342 mg/（L min））. Furthermore, cycling photodegradation ex-periments confirmed the stability and reusability of this catalyst. The unique physicochemical properties resulting from the low-temperature preparation of TiO2 -180℃, including its broadband visible absorption associated with a high concentration of oxygen vacancies, large surface area, and enriched surface -OH/H2O may be responsible for this excellent photocatalytic performance. The use of as-prepared TiO2 -180℃ for practical applications is expected after further optimization.

Novel visible-light-responding InVO_4-Cu_2O-TiO_2 ternary nanoheterostructure: Preparation and photocatalytic characteristics

A novel visible-light-responding InVO4-Cu2O-TiO2 ternary nanoheterostructure was designed on the basis of the strategy of energy gap engineering and prepared through ordinary wet chemistry methods. The as-prepared nanoheterostructure was characterized by X-ray powder diffraction（XRD）, transmission electron microscopy（TEM）, high-resolution transmission electron microscopy（HRTEM） and diffuse reflectance ultraviolet-visible spectroscopy（UV-vis/DRS）. The TEM and HRTEM images of 10%InVO4-40%Cu2O-50%TiO2 confirm the formation of nanoheterostructures resulting from contact of the nanosized TiO2, Cu2O and InVO4 in the size of 5–20 nm in diameter. The InVO4-Cu2O-TiO2 nanoheterostructure, when compared with TiO2, Cu2O, InVO4, InVO4-TiO2 and Cu2O-TiO2, shows significant enhancement in the photocatalytic performance for the degradation of methyl orange（MO） under visible-light irradiation. With a 9 W energy-saving fluorescent lamp as the visible-light source, the MO degradation rate of 10%InVO4-40%Cu2O-50%TiO2 reaches close to 90% during 5 h, and the photocatalytic efficiency is maintained at over 90% after six cycles. This may be mainly ascribed to the matched bandgap configurations of TiO2, Cu2O and InVO4, and the formations of two p-n junctions by the p-type semiconductor Cu2O with the n-type semiconductors TiO2 and InVO4, all of which favor spatial photogenerated charge carrier separation. The X-ray photoelectron spectroscopy（XPS） characterization for the used 10%InVO4-40%Cu2O-50%TiO2 reveals that only a small shakeup satellite peak appears for Cu（II） species, implying bearable photocorrosion of Cu2O. This work could provide new insight into the design and preparation of novel visible-light-responding semiconductor composites.

Degradation of dyestuff wastewater using visible light in the presence of a novel nano TiO_2 catalyst doped with upconversion luminescence agent

A new upconversion luminescence agent, 40CdF2·60BaF2·0.8ErO3, was synthesized and its fluorescent spectra were determined. This upconversion luminescence agent can emit five upconversion fluorescent peaks shown in the fluorescent spectra whose wavelengths are all below 387 nm under the excitation of 488 nm visible light. This upconversion luminescence agent was mixed into nano rutile TiO2 powder by ultrasonic and boiling dispersion and the novel doped nano TiO2 photocatalyst utilizing visible light was firstly prepared. The doped TiO2 powder was charactered by XRD and TEM and its photocatalytic activity was tested through the photocatalytic degradation of methyl orange as a model compound under the visible light irradiation emitted by six three basic color lamps. In order to compare the photocatalytic activities, the same experiment was carried out for undoped TiO2 powder. The degradation ratio of methyl orange in the presence of doped nano TiO2 powder reached 32.5% under visible light irradiation at 20 h which was obviously higher than the corresponding 1.64% in the presence of undoped nano TiO2 powder, which indicate the upconversion luminescence agent prepared as dopant can effectively turn visible lights to ultraviolet lights that are absorbed by nano TiO2 particles to produce the electron-cavity pairs. All the results show that the nano rutile TiO2 powder doped with upconversion luminescence agent is a promising photocatalyst using sunlight for treating the industry dye wastewater in great force.

Preparation and visible photocatalytic dye degradation of Mn-TiO2/sepiolite photocatalysts

The performance of Mn-TiO2/sepiolite photocatalysts prepared by the solgel method and calcinated at different temperatures was studied in the photocatalytic degradation of direct fast emerald green dye under visible light irradiation,and a series of analytical techniques such as XRD,SEM,FTIR,TG-DSC,XPS,UV-vis-DRS and Raman spectroscopy were used to characterize the morphology,structure and optical properties of the photocatalysts.It is found that the anatase TiO2 was formed in all photocatalysts.Mn4+might incorporate into the lattice structure of TiO2 and partially replace Ti4+,thus causing the defects in the crystal structure and the broadening of the spectral response range of TiO2.At the same time,TiO2 particles were dispersed on the surface of the sepiolite,which immobilized TiO2 particles with sepiolite via the bond of Ti-O-Si.Mn-TiO2/sepiolite calcined at 400°C exhibits the highest photocatalytic activity and the degradation rate of direct fast emerald green is up to 98.13%.Meanwhile,it also shows good stability and universality.

Large-Scale Synthesis of Porous Bi2O3 with Oxygen Vacancies for Efficient Photodegradation of Methylene Blue

Photocatalytic degradation of organic pollutants has become a hot research topic because of its low energy consumption and environmental-friendly characteristics.Bismuth oxide(Bi2O3)nanocrystals with a bandgap ranging from 2.0 eV to 2.8 eV have attracted increasing attention due to high activity of photodegradation of organic pollutants by utilizing visible light.Though several methods have been developed to prepare Bi2O3-based semiconductor materials over recent years,it is still difficult to prepare highly active Bi2O3 catalysts in large scale with a simple method.Therefore,developing simple and feasible methods for the preparation of Bi2O3 nanocrystals in large scale is important for the potential applications in industrial wastewater treatment.In this work,we successfully prepared porous Bi2O3 in large scale via etching commercial Bi Sn powders,followed by thermal treatment with air.The acquired porous Bi2O3 exhibited excellent activity and stability in photocatalytic degradation of methylene blue.Further investigation of the mechanism witnessed that the suitable band structure of porous Bi2O3 allowed the generation of reactive oxygen species,such as O2^-·and·OH,which effectively degraded MB.

A Highly Efficient and Stable Visible-Light Plasmonic Photocatalyst Ag-AgCl/CeO₂

Noble metal Ag nanoparticles with unique surface plasmon resonance property have attracted much attention recently in the field of photocatalysis. Based on the advantages of Ag nanoparticles and semiconductor CeO2, a novel plasmonic photocatalyst Ag-AgCl/CeO2 was prepared with a facile route. The as-prepared samples were characterized using scanning and transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis diffusion re?ection spectroscopy. This metal-semiconductor nanocomposite plasmonic photocatalyst exhibited a high visible-light photocatalytic activity and good stability for photocatalytic degradation of methyl orange in water. Ag-AgCl/CeO2 will be a potentially promising plasmonic photocatalysts for organic pollutant degradation and water purification.

Plasmonic Au nanoparticles supported on both sides of Ti02 hollow spheres for maximising photocatalytic activity under visible light

A strategy of intensifying the visible light harvesting ability of anatase Ti02 hollow spheres(HSs)was developed,in which both sides of Ti02 HSs were utilised for stabilising Au nanoparticles(NPs)through the sacrificial templating method and convex surface-induced confinement.The composite structure of single Au NP yolk-Ti02 shell-Au NPs,denoted as Au@Au(Ti02,was rendered and confirmed by the transmission electron microscopy analysis.Au@Au(Ti02 showed enhanced photocatalytic activity in the degradation of methylene blue and phenol in aqueous phase under visible light surpassing that of other reference materials such as Au(Ti02 by 77%and Au@P25 by 52%,respectively,in phenol degradation.

In situ preparation of g-C_(3)N_(4)/polyaniline hybrid composites with enhanced visible-light photocatalytic performance

The graphic carbon nitride/polyaniline(g-C_(3)N_(4)/PANI)hybrid composites were successfully synthesized by a facile in situ polymerization process under ice water bath.The photocatalytic activities of the g-C_(3)N_(4)/PANI composites were evaluated by using oxytetracycline(OTC)as model pollutants.The optimal g-C_(3)N_(4)/PANI composite(5%PANI:the g-C_(3)N_(4)/PANI hybrid with 5 wt.%of PANI)showed an enhancement degradation rate of 5-fold compared to that of conventional g-C_(3)N_(4)under simulated-sunlight irradiation.In addition,the 5%PANI demonstrate significantly photocatalytic evolution H_(2)rate(163.2μmol/(g·hr))under the visible light irradiation.Furthermore,based on the results of optical performance and electrochemical testing,a possible mechanism was proposed,indicating that the incorporation of PANI into the traditional g-C_(3)N_(4)can effectively tune the electronic structures,improve the photo-generated electrons-holes separation and enhance extensive absorption of visible light.Such a g-C_(3)N_(4)/PANI hybrid nanocomposites could be envisaged to possess great potentials in practical wastewater treatment and water splitting.

Synthesis of sponge-like TiO_(2) with surface-phase junctions for enhanced visible-light photocatalytic performance

Maximizing adsorption and catalytic active sites and promoting the photo-excited charge separation are two key factors to achieve excellent photocatalytic performance.In this study,we report a sol-gel synthesis approach to obtain non-metal doped TiO_(2)with sponge-like structure and surface-phase junctions all at once.While doping of carbon and nitrogen shifted the activation wavelength to the visible-light region,the innovative use of perchloric acid as a pore-making agent led to the formation of three-dimensional lamellar and porous structure with surface-phase junctions.High surface area with catalytic active sites rendered by the sponge-like structure and surface-phase junctions contributed to the much improved photocatalytic degradation efficiency toward rhodamine B,tetracycline and Disperse Red 60 with excellent reusability and stability.The improved gen eration and separati on efficie ncy of the photo-induced charge carriers of the as-prepared TiO_(2)were supported by electrochemical impedance measurements and transient photocurrent responses.This method could also be applied to other photocatalysts to achieve structural alteration and element doping simultaneously.

Facile low-temperature supercritical carbonization method to prepare high-loading nickel single atom catalysts for efficient photodegradation of tetracycline

Environmental photocatalysis is a promising technology for treating antibiotics in wastewater.In this study,a supercritical carbonization method was developed to synthesize a single-atom photocatalyst with a high loading of Ni(above 5 wt.%)anchored on a carbonnitrogen-silicate substrate for the efficient photodegradation of a ubiquitous environmental contaminant of tetracycline(TC).The photocatalyst was prepared from an easily obtained metal-biopolymer-inorganic supramolecular hydrogel,followed by supercritical drying and carbonization treatment.The low-temperature(300℃)supercritical ethanol treatment prevents the excessive structural degradation of hydrogel and greatly reduces the metal clustering and aggregation,which contributed to the high Ni loading.Atomic characterizations confirmed that Ni was present at isolated sites and stabilized by Ni-N and Ni-O bonds in a Ni-(N/O)_(6)-C/SiC configuration.A 5%Ni-C-Si catalyst,which performed the best among the studied catalysts,exhibited a wide visible light response with a narrow bandgap of 1.45 eV that could efficiently and repeatedly catalyze the oxidation of TC with a conversion rate of almost 100% within 40 min.The reactive species trapping experiments and electron spin resonance(ESR)tests demonstrated that the h+,and·O_(2)-were mainly responsible for TC degradation.The TC degradation mechanism and possible reaction pathways were provided also.Overall,this study proposed a novel strategy to synthesize a high metal loading singleatom photocatalyst that can efficiently remove TC with high concentrations,and this strategy might be extended for synthesis of other carbon-based single-atom catalysts with valuable properties.

多孔陶瓷负载Ce-TiO_(2)光催化降解印染废水研究

本文以建筑废弃物为主要原料,氧化铝为铝源,氟化铝为晶须催化剂,氧化硼、氧化铈、三氧化钼为烧结助剂,玉米淀粉为造孔剂,采用干压成型法制备了莫来石多孔陶瓷,研究了氧化铈和三氧化钼掺量对莫来石多孔陶瓷结构及理化性能的影响,并以性能最佳的陶瓷负载TiO_(2)/Ce-TiO_(2)进行光催化降解模拟印染废水研究。结果表明:以质量分数计,当氧化铈掺量为4%、三氧化钼掺量为1%时,多孔陶瓷的抗折强度为8.69 MPa,开口孔隙率为64.25%;负载0.05 g Ce-TiO_(2)催化剂,掺入1.2 mmol/L的PMS,在功率为18 W、波长为420~430 nm的LED可见光灯照射120 min后,其对亚甲基蓝溶液降解率达到96.62%。

三元复合物Ag/Cu_(2)O/g-C_(3)N_(4)的制备及其光催化降解和抗菌性能研究

以尿素、硫酸铜、乙酸银为原料,采用溶液法制备了三元复合物Ag/Cu_(2)O/g-C_(3)N_(4),通过XRD、XPS、SEM、TEM、UV-Vis等手段对三元复合物的结构进行了表征;以罗丹明B为模型研究了三元复合物的光催化降解性能,以大肠杆菌和金黄色葡萄球菌为模型研究了三元复合物的抗菌性能,并探究了三元复合物的光催化降解机理。结果表明,Ag和Cu_(2)O粒子沉积在g-C_(3)N_(4)片层结构上,Ag、Cu_(2)O和g-C_(3)N_(4)三者之间的协同作用使得三元复合物的光催化降解性能和抗菌性能大幅提高。为构建用于实际水体污染处理的g-C_(3)N_(4)基复合材料提供了新思路。

红磷光催化剂在废水处理领域的研究进展

目前半导体光催化处理废水已成为目前解决环境污染的有效途径之一。红磷作为一种非金属新型半导体光催化剂,具有价格低廉、低毒、易得、化学性质稳定、可见光响应范围广、带隙可调等优点。但存在光催化过程中稳定性较低,电子与空穴利用率不高等问题,因此,制备高效稳定的红磷基复合材料在实际应用中有着非常重要的意义。本文简述了红磷的结构,红磷基降解有机污染物的机理,详细总结了近几年红磷基在废水处理方面的研究现状,归纳了不同红磷基光催化效果,并通过从红磷结构、尺寸、异质结、协同作用对不同红磷基复合材料的光催化效率进行了分析。提出未来的研究方向应从改进红磷的制备方法,加强对晶型红磷以及红磷自身氧化机理等方面进行深入研究。

碳量子点修饰的BiOCl/MIL-101的光催化性能研究

采用常温水解法制备出碳量子点(CQDs)修饰的BiOCl/MIL-101(CBM)光催化剂,并探究其光催化降解抗生素性能。通过X射线衍射仪、扫描电子显微镜、氮气吸附-脱附仪和固体荧光仪等对所制备样品的结构、形貌、比表面积和电子-空穴分离情况等进行表征分析。结果表明:CQDs/BiOCl(CB)和MIL-101复合后制备的CBM光催化剂结晶性良好,形貌规整,大小均匀,具有较大的比表面积和较低的光生电子-空穴复合率,从而表现出更高的光催化性能。通过对盐酸环丙沙星的降解实验,发现其在可见光照射180 min后降解率提高了一倍。因此,铋基金属有机框架材料(Bi-MOF)在光催化领域有很大的应用空间。

Au改性纳米TiO_2材料对NPE-10光催化降解的活性

以钛酸四丁酯和氯金酸为原料,通过溶胶-凝胶法制备了Au掺杂的纳米TiO2光催化剂粉体,并用XRD、BET、XPS和固体紫外可见吸收光谱等技术对其晶相结构、比表面积、表面组成及紫外可见光响应范围进行了表征,对其光催化降解非离子表面活性剂壬基酚聚氧乙烯醚(NPE-10)的活性进行了考察.结果表明,掺杂的Au在纳米TiO2粉体材料中可能以两种形态存在,即以Au3+离子形式替代Ti4+进入TiO2晶格和以Au原子态形式暴露于粉体表面.前者使TiO2在480～650nm出现了更强的光吸收;后者中处于表面原子态的Au又会成为光生电子的受体,有效地避免了光生电子空穴对的复合.通过对掺杂量及处理温度的优化,在nAu3+/nTi4+=0.005,500℃煅烧的条件下可以制得具有较高的光催化活性的Au/TiO2粉体.对NPE-10的光催化氧化试验显示,日光照射4h后降解效率可以达到91.8%;而用未改性的纳米TiO2,在同样条件下,NPE-10的光催化降解效率仅能达到50.2%,商品DegussaP-25也只能达到66%.