Fazhou Wang

An in-situ synthesis of Ag/AgCl/TiO2/hierarchical porous magnesian material and its photocatalytic performance.

The absorption ability and photocatalytic activity of photocatalytic materials play important roles in improving the pollutants removal effects. Herein, we reported a new kind of photocatalytic material, which was synthesized by simultaneously designing hierarchical porous magnesian (PM) substrate and TiO2 catalyst modification. Particularly, PM substrate could be facilely prepared by controlling its crystal phase (Phase 5, Mg3Cl(OH)5·4H2O), while Ag/AgCl particles modification of TiO2 could be achieved by in situ ion exchange between Ag+ and above crystal Phase. Physiochemical analysis shows that Ag/AgCl/TiO2/PM material has higher visible and ultraviolet light absorption response, and excellent gas absorption performance compared to other controls. These suggested that Ag/AgCl/TiO2/PM material could produce more efficient photocatalytic effects. Its photocatalytic reaction rate was 5.21 and 30.57 times higher than that of TiO2/PM and TiO2/imporous magnesian substrate, respectively. Thus, this material and its intergration synthesis method could provide a novel strategy for high-efficiency application and modification of TiO2 photocatalyst in engineering filed.

Study on the Mechanism of Desorption Behavior of Saturated Sap in Concrete

The effect of several potential factors on the desorption behavior of saturated superabsorbent polymers (SAPs) in concrete was studied by simulating the internal saline concentration, alkalinity, and relative humidity. Results indicate that the desorption of SAP is mainly decided by osmotic pressure and humidity gradient. The desorption process of SAP is divided into three stages: the leading factor is the osmotic pressure during the first stage; humidity gradient during the third stage; and a relatively low-level combination of these two factors during the second stage. At the same time, the desorption is not decided by pH value, and the factor with the most effect is the osmotic pressure. The water release rate Rt of saturated SAP influenced by humidity shows the following trends: Rt indicates a clear linear trend as a function of time, and an approximate logarithm correlation exists between Rt and the relative humidity (Rt = A • ln(RH) + B).

Microstructure and Characteristic of BiVO4 Prepared under Different pH Values: Photocatalytic Efficiency and Antibacterial Activity

In the present study, BiVO4 sample was prepared under different pH 0.5–13 without capping agent. Different morphology characteristics were observed, such as sheet crystal structure, cross crystal structure and branching crystal structure. The mechanism of the formation of BiVO4 nanostructure was discussed. Under acid condition, sheet crystal structure was obtained. The phenomenon could be attributed to polymerization of vanadate in the presence of H+. In the weak alkaline solution, across structure and branching type morphology was obtained. The photocatalytic efficiency for the samples ranked as pH 5 > pH 3 > pH 7 > pH 9 > pH 1 > pH 11 > pH 13 > blank, which is in good agreement with X-ray diffraction (XRD) result. E. coli envelop was damaged in the presence of BiVO4 under visible light. The protrusion on envelop was diminished by BiVO4. Attenuated Total Reflection Fourier transformed Infrared Spectroscopy (ATR-FTIR) results suggested the intensity was weakened for the amide, phosphoric, –COO− group and C-H bond in lipopolysaccharides (LPS), peptidoglycan and periplasm molecules.

TiO 2 @Ag修饰的粉煤灰微集料增强水泥基材料光催化性能

Abstract A TiO 2 photocatalyst is coated on the surface of a zeolite fly ash bead (ZFAB) to improve its dispersability and exposure degree in a cement system. The application of Ag particles in TiO 2 /ZFAB modified cementitious materials is to further enhance the photocatalytic performance. Various Ag@TiO 2 /ZFAB modified cementitious specimens with different Ag dosages are prepared and the characteristics and photocatalytic performance of the prepared samples are investigated. It is observed that the multi-level pore structure of ZFAB can improve the exposure degree of TiO 2 in a cement system and is also useful to enhance the photocatalytic efficiency. With an increment of the amounts of Ag particles in the TiO 2 /ZFAB modified cementitious samples, the photocatalytic activities increased first and then decreased. The optimal Ag@TiO 2 /ZFAB modified cementitious sample reveals the maximum reaction rate constant for degrading benzene (9.91 × 10 −3 min −1 ), which is approximately 3 and 10 times higher than those of TiO 2 /ZFAB and TiO 2 modified samples, respectively. This suggests that suitable Ag particles coupled with a ZFAB carrier could effectively enhance the photocatalytic effects and use of TiO 2 in a cement system. Thus, ZFAB as a carrier could provide a potential method for a high efficiency engineering application of TiO 2 in the construction field.

Different Roles of Water in Photocatalytic DeNOx Mechanisms on TiO2: Basis for Engineering Nitrate Selectivity?

The nitrate selectivity of TiO2 has important consequences for its efficiency as a NOx depollution photocatalyst. Most emphasis is typically given to photocatalyst activity, a measure of the rate at which NOx concentrations are reduced, but a reduction in NOx concentration (mainly NO + NO2) is not necessarily a reduction in atmospheric NO2 concentration because the catalytic process itself generates NO2. With NO2 being considerably more toxic than NO, more emphasis on nitrate selectivity, a measure of the NOx conversion to nitrate, and how to maximize it, should be given in engineering photocatalytic systems for improved urban air quality. This study, on the importance of adsorbed water in the photocatalytic oxidation of NOx, has identified important correlations which differentiate the role that water plays in the oxidation of NO and NO2. This observation is significant and offers insights into controlling nitrate selectivity on TiO2 and the potential for increased effectiveness in environmental photocatalyst applications.

Degradation of formaldehyde and benzene by TiO2 photocatalytic cement based materials

A novel photocatalytic cement based material was prepared. The distribution of TiO2 on the surface of cement was characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD), which showed the relationship of photocatalysis and presence of TiO2. TiO2 also had an impact on cement hydration, which was studied by thermal analysis. With 300 W UV illuminations, formaldehyde and benzene were degraded efficiently by the prepared photocatalytic cement based materials. 15wt% TiO2/cement showed the highest degradation efficiency and capability. The results show that formaldehyde and benzene can be degraded within 4 and 9 hours, respectively. Besides, inorganic ions can induce TiO2 agglomeration. As a result, the presence of inorganic ions in cement is unfavorable for degradation. The photocatalytic cement based materials were fabricated and the degradation efficiency of formaldehyde was measured on building roof under sunlight illumination. Formaldehyde in glass chamber can be degraded thoroughly within 10 days.

The Effect of Interfacial Chemical Bonding in TiO2-SiO2 Composites on their Photocatalytic NOx Abatement Performance

The chemical bonding of particulate photocatalysts to supporting material surfaces is of great importance in engineering more efficient and practical photocatalytic structures. However, the influence of such chemical bonding on the optical and surface properties of the photocatalyst and thus its photocatalytic activity/reaction selectivity behavior has not been systematically studied. In this investigation, TiO2 has been supported on the surface of SiO2 by means of two different methods: (i) by the in situ formation of TiO2 in the presence of sand quartz via a sol-gel method employing tetrabutyl orthotitanium (TBOT); and (ii) by binding the commercial TiO2 powder to quartz on a surface silica gel layer formed from the reaction of quartz with tetraethylorthosilicate (TEOS). For comparison, TiO2 nanoparticles were also deposited on the surfaces of a more reactive SiO2 prepared by a hydrolysis-controlled sol-gel technique as well as through a sol-gel route from TiO2 and SiO2 precursors. The combination of TiO2 and SiO2, through interfacial Ti-O-Si bonds, was confirmed by FTIR spectroscopy and the photocatalytic activities of the obtained composites were tested for photocatalytic degradation of NO according to the ISO standard method (ISO 22197−1). The electron microscope images of the obtained materials showed that variable photocatalyst coverage of the support surface can successfully be achieved but the photocatalytic activity towards NO removal was found to be affected by the preparation method and the nitrate selectivity is adversely affected by Ti-O-Si bonding.

The Visible Light Photocatalytic Activity and Antibacterial Performance of Ag/AgBr/TiO2 Immobilized on Activated Carbon

Visible‐light‐driven Ag/AgBr/TiO2/activated carbon (AC) composite was prepared by solgel method coupled with photoreduction method. For comparison, TiO2, TiO2/AC, and Ag/AgBr/TiO2 were also synthesized. Their characteristics were analyzed by XRD, SEM‐EDS, TG‐DSC and UV–vis techniques. Photocatalytic activity and antibacterial performance under visible‐light irradiation were investigated by ICP‐AES, ATR‐FT‐IR and spectrophotometry methods using methylene blue and Escherichia coli as target systems, respectively. The results showed that Ag/AgBr was successfully deposited on anatase TiO2/AC surface, and exhibited a distinct light absorption in the visible region. Ag/AgBr/TiO2/AC displayed excellent antibacterial performance both in dark and under visible‐light illumination. The growth of E. coli cell was inhibited in the presence of Ag/AgBr/TiO2/AC in dark. Moreover, upon visible‐light illumination, a significant damage of cell membrane was noticed. Ag/AgBr/TiO2/AC was also shown higher photocatalytic efficiency for methylene blue degradation than those of TiO2, TiO2/AC, and Ag/AgBr/TiO2. This is attributed to the synergetic effect between AC and Ag/AgBr/TiO2, of which AC acts as the role of increasing reaction areas, continuous enriching, and transferring the adsorbed MB molecules to the surface of supported photocatalysts, and the Ag/AgBr/TiO2 acts as a highly active photocatalyst for degrading MB molecules under visible‐light irradiation.

Preparation and Design of Function Aggregate in Concrete

In order to essentially improve interfacial transition zone between cement paste and aggregate, the concept and ideal model of function aggregate are developed. Function aggregate is composed of a porous matrix with high strength and low water absorption, and a coating layer which can hydrate in cement paste. It can improve ITZ between aggregate and cement paste and control curing range of cement paste. Based on optimization of raw materials and processing techniques, high strength aggregate with low absorption and minor C2S and C4AF phase in coating layer is acquired. Results indicate that cordierite is formed in aggregate when MgO content reaches 2%, and it shows that the presence of cordierite minimizes the potential for micro-crack formation, thus decreases water absorption.

Improvement of the FRP sheet bonded to concrete substrate by silane coupling agent

We experimentally studied the fine lightweight aggregate with the particle size range of 3.15-4.75 mm used as functional bridge between FRP sheet and concrete substrate. However, problems would appear and how to deal with the interfacial transition zone (ITZ) and make it stronger is the key point for this concept. Considering that silane coupling agent (SCA) can provide a better bond on a silicon-containing material surface, it was introduced as a modifying material to further improve the bond quality of the ITZ between lightweight aggregate and cement paste. Results indicated that the water absorptivity of lightweight aggregate can be controlled by SCA solutions, and the pull-off bond strength, mechanical strength, and microhardness were increased, which was attributed to the optimized microstructure under the condition of an appropriate concentration of SCA.