Ag/ZnO-C nanocomposite-preparation and photocatalytic properties

In this present study, Ag-hybridized ZnO was prepared through a powder-sol method first, then Ag/ZnO-AC (activated carbon) composite was synthesized by a adsorption method using Ag/ZnO and AC as precursors. The structure and morphology of as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectrum (FT-IR), Raman spectra, and diffuse reflectance absorption spectra, respectively. The photocatalytic performances of the prepared catalysts were investigated by photocatalystic degradation of methyl orange. The influences of initial pH value, initial dye concentration and the calcination temperature on the photocatalytic activity of the catalysts were investigated and the results were discussed. Comparing with pure ZnO and ZnO-AC, Ag/ZnO-AC composite showed greatly enhanced photocatalytic activity. The results demonstrate that the hybridization of silver, activated carbon and ZnO can significantly improve the photocatalytic activity of ZnO. This work could provide new insights into the fabrication of noble metal/ZnO-carbon based composites and facilitate their application in environmental protection issues.     

Photocatalytic degradation of indigo carmine dye using TiO<Subscript>2</Subscript> impregnated activated carbon

The photocatalytic degradation of indigo carmine dye was studied using hydrothermally prepared TiO₂ impregnated activated carbon (TiO₂: AC). A comparison between the degradation of the indigo carmine dye using commercial TiO₂ and TiO₂: AC revealed the efficiency of the title compound. The degradation reaction was optimized with respect to the dye concentration and catalyst amount. The reduction in the chemical oxygen demand (COD) revealed the mineralization of dye along with colour removal. The active compound like TiO₂ was impregnated onto the activated carbon surface under mild hydrothermal conditions (<250°C, P ∼ 40 bars). The impregnated activated carbon samples were characterized using powder X-ray diffraction (XRD) and scanning electron microscope (SEM).     

Hydrothermal preparation of ZnO:CNT and TiO<Subscript>2</Subscript>:CNT composites and their photocatalytic applications

ZnO:CNT and TiO₂:CNT composites were fabricated under mild hydrothermal conditions (T = 150–240 °C) with an autogenous pressure. The as prepared composites were characterized using X-ray diffraction, Scanning electron microscopy and FTIR spectroscopy. Photocatalytic applications of the composites were investigated using indigo caramine dye. The effect of the catalyst content, pH of the medium, source and intensity of illumination on the photodegradation of the indigo caramine dye was studied and the efficiency of the composites were investigated based on different parameters like percent transmittance (%T), percent decomposition, and chemical oxygen demand of the dye solution to obtain optimum treatment conditions. The results obtained exhibit higher photocatalytic activity when compared to the reagent grade ZnO, TiO₂ and hydrothermally prepared ZnO:AC and TiO₂:AC composites.     

炭表面改性对负载型TiO_2/活性炭复合光催化剂性能的影响

采用HNO3、H2O2和O3对商品活性炭进行表面改性处理,考察了改性处理对活性炭表面基团、负载TiO2以及所形成的TiO2/活性炭复合光催化剂性能的影响。利用傅里叶红外光谱(IR)、X射线光电子能谱(XPS)、扫描电镜(SEM)及氮气吸附等手段对材料进行了表征。结果表明,3种改性方法均可有效提高活性炭载体表面的含氧官能团数量,但是对活性炭的比表面积和孔容影响不大;H2O2和O3对活性炭载体改性后可以提高对钛前驱体的吸附性能,HNO3改性有利于TiO2颗粒在活性炭表面的分散。使用改性后的活性炭作为载体制备的TiO2/活性炭光催化降解甲基橙的性能均高于未改性的TiO2/活性炭催化剂,其中以HNO3改性后的TiO2/活性炭活性最高。     

Photocatalytic degradation of Malachite Green dye by modified ZnO nanomaterial

In this article we report a chemical sol–gel approach to synthesize zinc oxide nanomaterials capped with ethylene diamine tetra acetic acid (EDTA), citric acid and oleic acid, and to study the effect of the surface modification on their photocatalytic activity and the kinetics for the degradation of Malachite Green (MG) dye. The structural, optical and chemical features were systematically characterized by X-ray powder diffraction, scanning electron microscopy, Fourier transform infrared and UV–vis absorption spectroscopy. The objective of using the capping agents was to confine the size and control the growth and morphology of the nanomaterial. The smallest crystallite size was recorded as 29 nm for EDTA-capped rod-shaped ZnO. A comparison study of the effect of the three different capping surfactants on ZnO nanomaterial for photocatalytic degradation of MG dye under solar light showed that EDTA with higher denticity coordinated efficiently with the surface of ZnO nanocrystalline catalysts and hence demonstrated better decolouration of the dye under solar light. The dye degradation followed the psuedo-first-order kinetics. EDTA proved to be the best capping agent among all the three for ZnO nanomaterial.     

Magnetically separable composite photocatalyst with enhanced photocatalytic activity

A novel magnetically separable composite photocatalyst, anatase titania-coated magnetic activated carbon (TMAC), was prepared in this article. In the synthesis, magnetic activated carbon (MAC) was firstly obtained by adsorbing magnetic Fe₃O₄ nanoparticles onto the activated carbon (AC), and then the obtained MAC was directly coated by anatase titania nanoparticles prepared at low temperature (i.e. 75 °C). The prepared samples were characterized by XRD, SEM and vibrating sample magnetometer (VSM). The composite photocatalyst can be easily separated from solution by a magnet, its photocatalytic activity in degradation of phenol in aqueous solution also has dramatic enhancement compared to that of the neat titania.     

电气石/ZnO复合材料光催化机制

采用一步水热法制备电气石/ZnO的复合材料。利用X射线衍射仪、扫描电子显微镜、X射线荧光光谱仪、UV-Vis DRS对样品的结构、形貌和光学性能进行表征。在可见光照射下,以酸性品红为降解物,研究电气石/ZnO复合材料的光催化性能,并通过动力学模型模拟酸性品红被降解的过程。结果表明:电气石加入并没有对ZnO的花瓣形貌产生影响,但对其光催化性能影响很大。随着电气石含量的增大,光催化性能先增长后降低。当电气石含量为5%(质量分数)时,光生电子-空穴复合概率降低,禁带宽度也下降,羟基自由基(·OH)的浓度增大,光催化效率达到最大96.62%,并且发现ZnO和电气石/ZnO复合材料的催化降解遵循一级动力学模型。     

Colloidal oxide nanoparticles for the photocatalytic degradation of organic dye

In this work, easily processable and highly crystalline ZnO and TiO₂ nanoparticles, with a narrow size distribution, obtained by using novel non-hydrolytic synthetic approaches were both tested for the photocatalyzed degradation of an organic dye, methyl red (2-(4-Dimethylamino-phenylazo)-benzoic acid)—C.I. 13020) and their behaviour comparatively examined with respect to TiO₂ and ZnO commercial powders. The experiments were carried out using semiconducting oxides under UV and visible light illumination. Preliminary studies on the influence of various experimental factors as pH and dye concentration were performed. The obtained results demonstrated a high photocatalytic efficiency of nanosized semiconducting particles.     

Preparation and photocatalytic activity of hollow ZnO and ZnO-CuO composite spheres

ZnO and ZnO-CuO composite hollow spheres were fabricated by using colloidal carbon spheres as templates. The morphology, structure and chemical composition of the as-prepared samples were investigated using field emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The photocatalytic activity of the hollow spherical products was evaluated by photocatalytic degradation of methylene blue (MB) aqueous solution at ambient temperature. The results indicated that the ZnO-CuO composite hollow spheres display higher photocatalytic efficiency than pure hollow ZnO products. The related photocatalytic mechanism was discussed based on the microstructure and properties of the ZnO and ZnO-CuO composite hollow spheres. The facile strategy for the preparation of ZnO-CuO hollow nanostructures can be applicable to the synthesis of other composite hollow spheres.     

Self-assembly of the Ag deposited ZnO/carbon nanospheres: A resourceful photocatalyst for efficient photocatalytic degradation of methylene blue dye in water

Carbon nanospheres (CNSs) are synthesized by pyrolysis of benzene at 1000?°C. Various UV-light photocatalysts of ZnO/CNSs and Ag-ZnO/CNSs (AZCN) composites are synthesized on the surface of CNSs using a facile chemical precipitation method. Morphological and optical properties of the as-synthesized photocatalysts are characterized by scanning electron microscopy, X-ray diffraction, energy dispersive spectroscopy, UV-Vis spectroscopy, photoluminescence and Raman spectroscopy. Photocatalytic degradation efficiency of methylene blue dye is investigated to examine the photocatalytic activity of synthesized photocatalysts. It is found that as-synthesized ZnO/CNSs composite can degrade higher methylene blue dye (～85.6%) after 25?min of UV irradiation in comparison with that of CNSs. A prominent improvement in the photodegradation is attained by depositing metal (Ag) particles on the surface of ZnO/CNSs composite. AZCN composite displays the enhanced photocatalytic degradation performance (～95% after 15?min of UV light) in high concentration of methylene blue dye. Furthermore, stability performance is studied by recycling the AZCN composite photocatalyst. It is found that the photocatalytic activity of AZCN composite is only slightly decreased even after five cycles. Present work demonstrates that AZCN composite show a great potential in the treatment of organic pollutants for wastewater treatment.     

Polymer-capped gold nanoparticles and ZnO nanorods form binary photocatalyst on cotton fabrics: Catalytic breakdown of dye

This work reports the immobilization of zinc oxide (ZnO) nanostructures and gold nanoparticles (AuNPs) on cotton fabrics (CFs). The ZnO and AuNPs containing CF composite materials demonstrated excellent photocatalytic activity towards degradation of the model organic dye molecule. A two-step method was used to first create zinc oxide nanorods (ZnONRs) on the CF fibers. Subsequently, these ZnONRs were decorated with cationic polymer-capped AuNPs to yield the composite materials. A one-pot synthetic route was developed to synthesize polymer-capped AuNPs. The water-soluble cationic polymers used here are polyguanidino oxanorbornenes (PGONs) at 20 kDa and polyamino oxanorbornenes (PAONs) at 20 kDa. UV–vis was utilized to monitor the composite materials’ photocatalytic activity in degrading model organic dye molecules. All the materials were characterized by FTIR, UV–visible DRS, SEM, EDX, and XRD. The composite materials exhibited excellent photocatalytic activity and recyclability in the presence of UV light.     

Simple fabrication of carbon/TiO2 composite nanotubes showing dual functions with adsorption and photocatalytic decomposition of Rhodamine B

Carbon/TiO2 composite nanotubes were fabricated via a very simple electrospinning process and their dual functionalities of adsorptivity and photocatalytic activity were evaluated using Rhodamine B (RhB) as a model organic pollutant. A poly(vinyl alcohol) (PVA) aqueous solution was directly electrospun into a coagulation bath containing titanium (IV) tetraisopropoxide (TTIP) solution so that PVA-core/TiO2-shell composite nanofibers were formed through the in situ sol-gel reaction of TTIP. The carbon/TiO2 composite nanotubes were then fabricated by heat treatment of composite nanofibers under nitrogen atmosphere. By using several characterization methods, we confirmed that the resultant nanotubes consisted of anatase TiO2 nanocrystallites embedded in a carbonaceous matrix. The prepared nanotubes exhibited fast adsorption of RhB with high capacity compared with a commercial porous carbon, and they also showed the photocatalytic decomposition activity for the dye molecules under UV irradiation comparable to the degradation by P-25 and ST-01 (commercial TiO2). Finally, the carbon/TiO2 composite nanotubes exhibited several cycle performances of adsorption-photodegradation for RhB. This indicates that the composite nanotubes can adsorb and photodecompose organic pollutants repeatedly without additional activating processes.     

Photocatalytic degradation of rhodamine B dye using hydrothermally synthesized ZnO

The sunlight mediated photocatalytic degradation of rhodamine B (RB) dye was studied using hydrothermally prepared ZnO (T = 150°C andP ∼ 20–30 bars). Zinc chloride was used as the starting material along with sodium hydroxide as a solvent in the hydrothermal synthesis of ZnO. Different durations were tried to obtain pure ZnO phase, which was later confirmed through powder X-ray diffraction. The photocatalytic behaviour of the prepared ZnO was tested through the degradation of RB. The disappearance of organic molecules follows first-order kinetics. The effect of various parameters such as initial dye concentration, catalyst loading, pH of the medium, temperature of the dye solution, on the photo degradation of RB were investigated. The thermodynamic parameters of the photodegradation of RB, like energy of activation, enthalpy of activation, entropy of activation and free energy of activation revealed the efficiency of the process. An actual textile effluent containing RB as a major constituent along with other dyes and dyeing auxiliaries was treated using hydrothermally synthesized ZnO and the reduction in the chemical oxygen demand (COD) of the treated effluent revealed a complete destruction of the organic molecules along with colour removal.     

含共轭结构的ZnO/聚乙烯醇复合光催化材料的制备与性能

以ZnO和NaOH为原料,采用低温水热法合成纳米ZnO 半导体材料,并与聚乙烯醇（PVA）水溶液在超声作用下混合,通过直接煅烧制备出PVA中含共轭双键碳链结构（C）的ZnO/PVA_C复合光催化材料。采用 SEM、XRD、FTIR、Raman和UV-Vis DRS对样品进行表征。结果表明:ZnO/PVA_C复合光催化材料由结晶性能良好的纳米ZnO和具有共轭结构的聚合物组成,且界面间通过化学键Zn-O-C相连接;在模拟太阳光照射下,ZnO/PVA_C复合光催化材料对光的吸收响应可扩展到整个可见光区,并产生较高光电流。光催化性能测试结果表明,ZnO/PVA_C复合光催化材料对罗丹明B的降解催化性能（30 min降解率接近于100%）明显高于纯纳米ZnO。      

Preparation and characterization of ZnO-graphene composite photocatalyst

ZnO is one of potential semiconductor materials in photocatalytic field, and appears to be a suitable alternative to TiO2, due to its photochemical properties and photodegradation mechanism similar to TiO2. Graphene is a single 2D carbon sheet with large specific surface and excellent electric conductivity. The combination of ZnO and graphene could extremely improve the photocatalytic activity of ZnO. Herein we prepared ZnO-graphene nanocomposite photocatalyst using graphite and ZnO by a facile one-step hydrothermal method. During the hydrothermal reactions, both of the reduction of graphene oxide and loading of ZnO were occurred simultaneously and the desired product was obtained. The as-prepared ZnO-graphene photocatalyst exhibited extraordinaire photocatalytic properties. Results of photocatalytic degradation of methyl orange show that the photocatalysis efficiency of the composite was significant enhanced, compared to pure ZnO. This work could provide new avenue for the fabrication of ZnO-carbon based composites, facilitating their application in pollutions degradation issues.     

Electrochemical-assisted photodegradation of mixed dye and textile effluents using TiO2 thin films

Mixed dye consists of six commercial dyes and textile effluents from cotton dyeing process were treated by electrochemical-assisted photodegradation under halogen lamp illumination. Two types of effluents were collected which are samples before and after undergone pre-treatment at the factory wastewater treatment plant. The photodegradation process was studied by evaluating the changes in concentration employing UV-vis spectrophotometer (UV-vis) and total organic carbon (TOC) analysis. The photoelectrochemical degradation of mixed dye was found to follow the Langmuir Hinshelwood pseudo-first order kinetic while pseudo-second order kinetic model for effluents by using TOC analyses. The chemical oxygen demand (COD) and biochemical oxygen demand (BOD) values of mixed dye and raw effluents were reported. Photoelectrochemical characteristic of pollutants was studied using the cyclic voltammetry technique. Raw effluent was found to exhibit stronger reduction behaviour at cathodic bias potential but slightly less photoresponse at anodic bias than mixed dye.     

Self-assembled 3D ACF–rGO–TiO2 composite as efficient and recyclable spongy adsorbent for organic dye removal

Reduced graphene oxide (rGO) nanosheets (NSs) decorated with TiO₂ nanoparticles (NPs) were bound to activated carbon fibers (ACF) forming three-dimensional (3D) macroscopic composites with nanoscale building blocks by a one-pot hydrothermal self-assembly method. The integration of adsorption capacity enhanced by rGO NSs and photocatalytic activity introduced by TiO₂ NPs in the resultant ACF–rGO–TiO₂ composite was demonstrated via the proof-of-concept application of disposing organic dyes, i.e. Rhodamine B (RhB). Moreover, the photocatalytic degradation of laden RhB dye can effectively make ACF–rGO–TiO₂ composites regenerate the adsorption capacity, promoting two practical values: (1) eliminating rather than removing dye pollutants and (2) recycling rather than consuming adsorbents. The synergistic functionalization highlights the potential of 3D ACF–rGO–TiO₂ composite as a promising massive adsorbent with photocatalytic activities for environment purifications.     

ZnO复合石墨相氮化碳纳米片的制备及其光催化性能研究

为了提高石墨相氮化碳光催化性能,本文以尿素、硫脲、醋酸锌为前驱体,通过氧化热剥离与共混煅烧法分别制备g-C₃N₄纳米片和ZnO/g-C₃N₄异质结复合材料,并采用TEM、FTIR、XRD、UV-Vis DRS、BET等表征手段对制备的催化剂进行结构表征。以罗丹明、大肠杆菌为探针,考察了催化剂的光催化降解性能和抑菌活性。结果表明：以尿素和硫脲为前驱体,经过氧化热剥离处理后能得到的g-C₃N₄ 2D纳米片,其比表面积更大、光催化性能更加优异,且其对罗丹明的降解率较未剥离的g-C₃N₄提高了21.2%。在40 min氙灯照射下,纯g-C₃N₄并未表现出良好的抑菌性能,而通过ZnO复合制备的ZnO/g-C₃N₄异质结复合材料,在光催化降解率和抑菌活性方面均有很大提高,其中复合20%ZnO制得的ZnO异质结复合材料表现出最佳的光催化性能...     

Effects of carbon content on the photocatalytic activity of C/BiVO4 composites under visible light irradiation

Carbon-loaded BiVO₄ composite photocatalysts were prepared using an impregnation method, and their ability to photocatalytically degrade Rhodamine B dye solution under visible light irradiation was investigated. The prepared composite photocatalysts were characterized by X-ray diffraction (XRD), field-emission electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller (BET) surface area measurements, and UV–vis diffuse reflectance spectra. We found that the carbon was well-dispersed on the surface of BiVO₄. The photocatalytic activity of the composite photocatalysts for the degradation of Rhodamine B (RhB) in aqueous solution under visible light irradiation (>420 nm) was higher than that of pure BiVO₄. Moreover, the degradation efficiency increased as the carbon content increased up to 3 wt%. The mechanism of enhanced photocatalytic activity is discussed with reference to surface area, optical absorption properties, and charge separation.     

Low-temperature preparation and microwave photocatalytic activity study of TiO2-mounted activated carbon

TiO2 thin films were deposited on granular activated carbon by a dip-coating method at low temperature (373 K), using microwave radiation to enhance the crystallization of titania nanoparticles. Uniform and continuous anatase titania films were deposited on the surface of activated carbon. BET surface area of TiO2-mounted activated carbon (TiO2/AC) decreased a little in comparison with activated carbon. TiO2/AC possessed strong optical absorption capacity with a band gap absorption edge around 360 nm. The photocatalytic activity did not increase when the as-synthesized TiO2/AC was thermally treated, but was much higher than commercial P-25 in degradation of phenol by irradiation of electrodeless discharge lamps (EDLs).