光触媒技术的发展与应用

光触媒(photocatalyst)在光的照射下具有净化、除臭、杀菌、防污的优良性能,得到了人们越来越多的重视。本文介绍了光触媒技术的反应机理,二氧化钛光触媒的特性及在各个领域的应用。     

Facile synthesis of ZnS/WO3 coupled photocatalyst and its application on sulfamethoxazole degradation

In this study, the coupled photocatalysts ZnS/WO₃ were synthesized by a simple co-precipitation method, varying the content of ZnS (1, 5, and 10 wt%). The obtained materials were characterized by X-ray diffraction (XRD), scanning electron microscopy coupled to energy dispersive spectroscopy (SEM-EDS), N₂ physisorption, UV–Vis with diffuse reflectance spectroscopy (DRS), atomic absorption (AAS), infrared (IR), and photoluminescence (PL) spectroscopies. Furthermore, the synthesized photocatalysts were evaluated on the photocatalytic degradation of sulfamethoxazole (SMX) under simulated sunlight. The activity of the different coupled photocatalysts ZnS/WO₃ was significantly improved compared to the individual semiconductors (ZnS and WO₃). This enhancement was attributed to the reduced recombination rate determined through PL analysis. The ZnS_5%/WO₃ photocatalyst exhibited the highest performance in comparison with the other coupled materials, achieving complete SMX degradation in 60 min. In combination, the enhanced specific surface area, high particle dispersion, and reduced recombination rate define the ZnS_5%/WO₃ photocatalyst as a suitable candidate for photocatalytic environmental applications.     

光催化剂改性及固定化技术的研究进展

提高光催化剂的光催化活性，以及将光催化剂固定于合适的载体表面，这是多相光催化技术工业处理应用中的关键。单一半导体光催化剂的光催化活性普遍不高，通过改性可以提高光催化活性，甚至在提高活性的同时扩展光谱响应范围，提高光的利用率。而将光催化剂固定在合适的载体表面，可免去光催化剂的分离回收工序，以及消除粉末悬浮体系中存在的易聚集、流失等缺点。     

Degradation of organic pollutants in water by photochemical reactors

The degradation of glycolic acid in aqueous media was performed by homogeneous photochemical and heterogeneous photocatalytic processes using different kinds of chemical reactors. The efficiency of the degradation processes was evaluated by measuring both the reactant conversion and the decrease of the total organic carbon (TOC) of the solution. The best results were obtained by using a continuous reactor with a fixed supported photocatalyst.     

纳米纤维膜在空气净化中的应用研究进展

面向空气净化的应用需要,开发高效净化材料已成为研究热点之一,其中具有相互连贯孔结构的纳米纤维膜在高效空气净化领域展示出巨大的应用前景。对于纳米纤维膜对空气净化效果的评估指标通常包括过滤效率和过滤阻力。本文介绍了串珠、蛛网和复合等结构纳米纤维膜的研究进展,分析了驻极式纳米纤维膜在高效除尘方面的应用现状,探讨了银纳米颗粒和半导体金属氧化物改性纳米纤维膜在抗菌和除有机易挥发性气体等多功能性空气净化中的应用可行性,指出了高效低阻、功能化是纳米纤维膜用于空气净化领域的研究重点。并提出今后应高度关注多污染物对纳米纤维空气净化膜性能的影响,深入研究具有多功能协同作用的纳米纤维空气净化膜,以期获得更广泛的应用。     

Indoor air purification by photocatalyst TiO2 immobilized on an activated carbon filter installed in an air cleaner

The enhancement effect of using TiO₂ immobilized on activated carbon (TiO₂/AC) filter for removing indoor air pollutant at parts-per-billion (ppb) levels has been previously reported. To further evaluate the TiO₂/AC filter for practical application, it was installed in an air cleaner available in the commercial market and tested inside an environmental chamber. Nitrogen oxide (NO) and toluene were selected as target pollutant. Results showed that a higher removal efficiency of NO was achieved using shorter wavelength ultraviolet lamp than longer wavelength ultraviolet lamp. A higher NO removal was achieved using TiO₂/AC filter compared to TiO₂ filter only. The intermediate, NO₂, generated from the photodegradation of NO was also successfully suppressed from exiting the system using TiO₂/AC filter. A 25% higher of nitrogen oxides (NO_x) was achieved using TiO₂/AC filter compared to the TiO₂/AC only. The higher removal efficiency of using TiO₂/AC is owing to the large adsorption capacity provided by the activated carbon. The adsorbed NO is then transferred to the TiO₂ for photodegradation. The difference in toluene removal efficiency using TiO₂/AC filter compared to the TiO₂ filter is even more significant.     

First-principles modeling, scaling laws and design of structured photocatalytic oxidation reactors for air purification

First-principles, predictive engineering models provide a sound theoretical basis for quantifying the inherent light energy utilization capabilities and performance limitations of candidate commercial photocatalytic oxidation reactor configurations. In particular, these models provide insight into the similarities and differences between photoreactors based on structured honeycombed monoliths, and those based on reticulated foams or other random catalyst supports.

For honeycombed monoliths, a deterministic first-principles radiation field model provides the channel wall light intensity profile down the length of a single channel in the monolith. A three-dimensional developing flow convection–diffusion reaction model employing this radiation field submodel predicts the velocity and concentration fields. The model shows that light intensity gradients in a monolith of typical dimensions are severe, that only a fraction of the monolith can be effectively photo-activated, and as a consequence process performance is largely controlled by light distribution. For a given light source and photocatalyst combination, reactor performance scales according to the aspect ratio of the channeled monolith, the Reynolds number, and the Dahmköhler number.

For randomly structured monoliths, the radiation field must be determined by probablistic methods. Monte Carlo simulations show that the radiation field in such random porous structure scales according to the pore size distribution and the void fraction, and the photocatalyst film thickness. Reactor performance scales by the radiation field, the Peclet number, the Stanton number, and the Dahmköhler number. The complex interrelationship between the random structure of the monolith and the resulting radiation field and mass transfer behavior makes scaling of these reactor types particularly difficult.     

Enhanced air filtration performance under high-humidity condition through electrospun membranes with optimized structure

The separation stability under high-humidity is significant in practical applications for air filters. Herein, hydrophobic polyvinyl chloride(PVC) nanofiber filters with bead-on-string structure are designed to steadily remove particle matter under high relative humidity of 90%–95%. The developed hydrophobic filters possess comparable separation performance with the hydrophilic one, but greatly enhanced stability. After the introduction of beadon-string structure, the filtration performance can be furtherly improved due to the formed large cavities and hydrophobicity. Such hydrophobic PVC filters can be promising candidates for air purification in practical applications especially in wet seasons.     

二氧化钛光触媒在金属镀膜与金属防护技术中的应用第四部分——光触媒的性能评价标准与高性能化

随着二氧化钛光触媒从研究领域走向实用,光触媒材料的评价标准问题逐渐受到重视。介绍了日本制定光触媒标准的现状以及实现光触媒的高性能化方法。以含或不含光触媒的乙醛试样在紫外光的照射下的分解速度对比试验说明了光触媒的空气净化性能的评价方法。     

室内观叶植物净化空气的研究进展

探讨了室内空气污染的分类和室内观赏植物净化各种室内空气污染的主要机理。分析近年来有关室内植物净化空气的研究与利用现状,提出了室内植物净化空气研究存在的问题与前景。     

Separation performance of thin-film composite nanofiltration membrane through interfacial polymerization using different amine monomers

Four kinds of thin-film composite (TFC) membranes were prepared via interfacial polymerization using diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA) and piperazidine (PIP) as water-soluble monomer, and trimesoyl chloride (TMC) as organic-soluble monomer. The surface chemical features of the resultant membranes were confirmed by contact angle measurement and Fourier transform infrared spectroscopy (FTIR). The membrane morphology and surface charges were investigated through Scanning electronic microscopy (SEM) and Zeta potential, respectively. Salt rejection was used to evaluate the separation performance of the four kinds of TFC membranes. The results showed that all the four kinds of TFC membranes exhibited typical negatively charged nanofiltration membrane characteristics. The salt rejections followed the sequence: Na₂SO₄ > MgSO₄ > MgCl₂ and the rejection of Na₂SO₄ was all over 80%. It was also found that the solubility of water-soluble monomer in organic solvent played an important role in manipulating the membrane structure, charge properties and thus the separation performance.     

载重斜交轮胎喷气牵引帘布筒成型机的研制

介绍了载重斜交轮胎喷气牵引帘布筒成型机的结构、性能及其主要特点。机由主机、尾架、扩布器、帘布筒上牵引装置、正反包装置、后压辊、底部压辊、胎面供料装置、气动系统、控制系统等部分组成,其喷气牵引帘布筒、胶囊内压控制及尾架平移技术系国内首次使用。该机不仅可提高载重斜交轮胎的成型特刊质量,而且单工操作强度适中,成型每条轮胎所需时间约５．５ｍｉｎ,班产可超过６５条。     

二氧化钛光触媒在金属镀膜与金属防护技术中的应用第一部分光触媒分散技术

介绍了二氧化钛的晶体类型和基本性质、典型的锐钛型二氧化钛的XRD图谱。对纳米粒子的团聚现象进行了解释。对纳米粒子的分散原理——高分子分散剂／界面活性剂分散和电解质分散进行了说明。分别介绍了水溶液中二氧化钛以及改性后的锐钛型纳米二氧化钛的Zeta电位与pH的关系。研究了锐钛型纳米二氧化钛在聚丙烯酸盐分散介质中的粒径分布。结果表明,在此分散介质中,纳米颗粒的分布比较集中,粒径小于50．7 nm的粒子占60％,其平均粒径远低于传统的涂料级和颜料级分散的粒子;该溶液呈现明显的丁达尔现象,光触媒活性高,在实验室存放24个月后质量稳定;将此溶胶涂至玻璃表面,所得涂膜透明度高。     

Hybrid photocatalysts for the degradation of trichloroethylene in air

Hybrid photocatalysts based on an adsorbent SiMgOx and a photocatalyst TiO₂ were developed in a plate shape. The ceramic surface was coated with TiO₂ by the slip-casting technique. The effect of the support in the photocatalytic degradation of trichloroethylene (TCE) was analyzed by modifying TiO₂ loading and the layer thickness. Photocatalysts were characterised by N₂ adsorption–desorption, mercury intrusion porosimetry, SEM, UV–vis spectroscopy and XRD. A direct relationship between the TiO₂ content and the photocatalytic activity was observed up to three layers of TiO₂ (0.66 wt.%). Our results indicate that intermediate species generated on the TiO₂ layer can migrate through relatively long distances to react with the OH⁻ surface groups of the support. By increasing the TiO₂ loading of the photocatalyst two effects were observed: trichloroethylene conversion is enhanced, while the efficiency of the oxidation process is decreased at expenses of increasing the selectivity to COCl₂ and dichloroacetylchloride (DCAC). The results are discussed in terms of the layer thickness, TiO₂ amount, TCE conversion and CO₂, and COCl₂ selectivity.     

Microfabrication, characterization and analytical application of a new thin-film silver microsensor

The present research demonstrates the microfabrication of a novel thin-film silver microelectrode based on an ion-selective PVC organic membrane. First, the gold substrate thin-film surface is treated by depositing a thin-layer of Ag electrochemically. This pretreatment step is followed by applying the organic-membrane-sensitive layer using a new nebulization technique, which gives a high stability to the organic-membrane-sensitive layer. The performance of the resulting thin-film silver microelectrode is investigated by potentiometric measurements. The microelectrode provides a linear Nernstian response of high sensitivity (58 ± 0.5 mV/decade) covering the range of 1 × 10⁻⁶-1 × 10⁻¹ mol L⁻¹ of Ag⁺ ions with a fast response time (<20 s) and a relatively long life span (>3 months). The suggested microelectrode is successfully used in the analytical evaluation of Cl⁻ ions in some real environmental samples as well as in the simultaneous determination of halides using potentiometric titration. The results obtained are compared with those obtained by the commercial silver billet electrode and the conventional bulk ion-selective electrode based on the same ionophore.     

Recent development and application of thin-film thermoelectric cooler

Recently, the performance and fabrication of thin-film thermoelectric materials have been largely enhanced. Based on this enhancement, the thin-film thermoelectric cooler (TEC) is becoming a research hot topic, due to its high cooling flux and microchip level size. To fulfill a thin-film TEC, interfacial problems are unavoidable, as they may largely reduce the properties of a thin-film TEC. Moreover, the architecture of a thin-film TEC should also be properly designed. In this review, we introduced the enhancement of thermoelectric properties of (Bi,Sb)₂(Te,Se)₃ solid solution materials by chemical vapor deposition, physical vapor deposition and electrodeposition. Then, the interfacial problems, including contact resistance, interfacial diffusion and thermal contact resistance, were discussed. Furthermore, the design, fabrication, as well as the performance of thin-film TECs were summarized.     

Water purification and toxicity control of chlorophenols by 3D nanofiber membranes decorated with photocatalytic titania nanoparticles

Highly photocatalytic water purification three-dimensional nanofiber membranes were fabricated. We identified the optimal fabrication process of nylon-6 nanofiber membranes suspending titania nanoparticles for potential water purifications and toxicity control of chlorophenols. Nanofibers and nanoparticles were deposited on a soda lime glass substrate by electrospinning and electrospraying, respectively. Titania nanoparticles were used to induce the UV light driven photocatalytic effect and nanofibers were used to tightly suspend the nanoparticles in air. Both batch and continuous deposition processes were introduced in the membrane fabrication process and their water purification performances were compared and quantified using a methylene blue solution, which is often used as a model pollutant. Surface morphologies and characteristics of the membranes fabricated at various process conditions were also provided. The membrane fabricated by the continuous means yielded 100% degradation of the methylene blue solution within 90 min under a relatively weak UV irradiation (0.6 mW/cm²), which promises its potential indoor application. The nano-textured membranes developed in this work was also applied to the real pollutants, such as chlorophenols, and showed a promising performance in their toxicity control.     

Construction of ternary Ag@ZnO/TiO2 fibrous membranes with hierarchical nanostructures and mechanical flexibility for water purification

Rational design of semiconductor membrane photocatalyst with good mechanical flexibility and excellent photocatalytic activity is of significance for environmental remediation. Herein, flexible Ag@ZnO/TiO₂ fibrous membranes with hierarchical nanostructures were fabricated through combining a simple electrospinning method and subsequent hydrothermal reaction and photodeposition process. In the ternary nanocomposite, ZnO nanorods were firmly anchored onto TiO₂ nanofibers, while Ag nanoparticles were evenly decorated on the surface of both ZnO and TiO₂. Benefiting from the improved light absorption, large surface area, and effective charge separation, the resultant Ag@ZnO/TiO₂ membranes displayed superior photocatalytic degradation efficiency of 91.6% toward tetracycline hydrochloride within 1 h, and also exhibited prominent antibacterial activity with a 6.5 log inactivation of E. coli after 1 h simulated solar light exposure. Significantly, the membrane photocatalyst still preserved structural integrity and mechanical flexibility after utilization. This study provides an alternative approach for designing and synthesizing flexible TiO₂-based membrane photocatalysts toward high-efficiency water purification.     

Strontium doping effects on the characteristics of solution-processed aluminum oxide dielectric layer and its application to low-voltage-operated indium-gallium-zinc-oxide thin-film transistors

In this paper, we investigated the strontium doping effects on the electrical and physical characteristics of solution-processed aluminum oxide dielectric layer and its application to low-voltage-operated indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs). With an optimized doping concentration of strontium (5 at%) in aluminum oxide (Al₂O₃), an oxide gate dielectric layer having a dielectric constant of ~7 and low leakage current characteristics (~4 × 10⁻⁷ A/cm² at 3 MV/cm) could be achieved by a solution process, which are comparably better than those of pristine Al₂O₃ film. The enhanced dielectric properties from strontium doping can be attributed to the change in the physical properties of Al₂O₃ film incorporated with strontium, providing charge relaxation of defect states in Al₂O₃ film. Also, since the strontium is highly reactive with oxygen, the strontium substitution through a doping leads to more strongly bound structure in an Al₂O₃ film without considerable lattice distortion. Using the strontium-doped aluminum oxide film as a gate dielectric layer, having a thickness less than 10 nm, solution-processed IGZO TFTs operating at ≤ 1 V were demonstrated showing a field-effect mobility of 1.74 ± 1.10 cm²/V s and an on-current level of ~10⁻⁵ A.     

气流负压新型剥丝装置的设计

针对现有化纤剥丝机存在的问题 ,应用引射原理 ,在保持控制线路基本不变的前提下 ,增加 1个二位三通电磁阀控制气源 ,设计了一套新型的气流负压剥丝装置。