Menglei Chang

A new insight into PAM/graphene-based adsorption of water-soluble aromatic pollutants

Graphene materials have been extensively verified as a good adsorbent for tackling wastewater containing various aromatic pollutants; however, little attention has been paid to understanding the graphene-based adsorption mechanism. Here, a systematic work is performed to prepare a series of graphene oxide (GO)-incorporated polyacrylamide hydrogels, with a three-dimensional (3D) monolithic structure, followed by in situ conversion of GO to reduced graphene oxide. Such a method not only enables the prevention of irreversible aggregation of graphene sheets during the in situ reduction, but also facilitates the clarification of the relationship between the structure and adsorption properties of the graphene materials. This work presents two kinds of graphene-based 3D monolithic adsorbents for either selective separation of the cationic aromatic pollutant from anionic one or uptake both of them for the total purification purpose. More importantly, we effectively unravel that the sp2-conjugated carbon network of the graphene materials plays a pivotal role in purifying the aromatic organic pollutants through π–π stacking interactions that outstrip electrostatic attraction interactions. Therefore, the present work is expected to provide an impetus toward exploration of high-performance graphene-based materials for various applications, especially environmental remediation, on the basis of effectively impeding self-aggregation of graphene sheets and judiciously modulating their intrinsic structure.

Cotton fabric-based facile solar photocatalytic purification of simulated real dye wastes

For the first time, this study presents solar photocatalytic processing of the real dye wastes remaining after finishing polyester/cotton (P/C) blends, rather than a pure organic dye solution as widely reported. A commonly used microencapsulation-based one-bath dyeing is investigated systematically, in order to simulate the real dyeing environment and to generate real dye wastes. The generated dye wastes are subsequently tackled by facile cotton fabric-based photocatalytic degradation involving a visible light-active TiO2 photocatalyst under solar light. Importantly, such a TiO2 photocatalyst is prepared without any calcination, doping, or coupling with plasmonic metal nanoparticles or narrow-band-gap semiconductors. As a result, the present visible light-responsive cotton fabric-based photocatalytic degradation of the simulated real dye wastes is expected to stimulate various industries for achieving simultaneous effective dyeing and processing of the dye wastes remained. This study also contributes to energy saving and environmental protection.

Improving Visible Light-Absorptivity and Photoelectric Conversion Efficiency of a TiO2 Nanotube Anode Film by Sensitization with Bi2O3 Nanoparticles

This study presents a novel visible light-active TiO2 nanotube anode film by sensitization with Bi2O3 nanoparticles. The uniform incorporation of Bi2O3 contributes to largely enhancing the solar light absorption and photoelectric conversion efficiency of TiO2 nanotubes. Due to the energy level difference between Bi2O3 and TiO2, the built-in electric field is suggested to be formed in the Bi2O3 sensitized TiO2 hybrid, which effectively separates the photo-generated electron-hole pairs and hence improves the photocatalytic activity. It is also found that the photoelectric conversion efficiency of Bi2O3 sensitized TiO2 nanotubes is not in direct proportion with the content of the sensitizer, Bi2O3, which should be carefully controlled to realize excellent photoelectrical properties. With a narrower energy band gap relative to TiO2, the sensitizer Bi2O3 can efficiently harvest the solar energy to generate electrons and holes, while TiO2 collects and transports the charge carriers. The new-type visible light-sensitive photocatalyst presented in this paper will shed light on sensitizing many other wide-band-gap semiconductors for improving solar photocatalysis, and on understanding the visible light-driven photocatalysis through narrow-band-gap semiconductor coupling.

Sealing Holes of an Anodic Aluminum Oxide Alloy by Nanotitania for Enhanced Corrosion Resistance

This study aims to explore an effective, novel, and environmentally friendly method that overcomes the limitations and shortcomings existing in the traditional approaches for sealing holes on aluminum alloy. Herein, the holesealing treatment of an Anodic Aluminum Oxide (AAO) alloy film using two types of titanium sources with a high stability in aqueous electrolytes, that is, ammonium fluorotitanate and titanium potassium oxalate, to electrically deposit nanotitania on the film surface was investigated. The nanotitania deposited electrochemically for hole sealing has the advantages of the high physiochemical stability, low cost, and non-toxicity, which can thus readily improve the corrosion resistance of the sealed AAO in an environmentally friendly manner. Such sealed AAO can also result in a UV-shielding performance due to the commonly-known UV absorption properties of nanotitania. The hole sealing effect is also compared between the two systems involving the two types of titanium sources at different concentrations, voltages and time. The optimization of the preparation conditions is achieved by means of weight loss measurements. Potentiodynamic scan and electrochemical impedance spectroscopy results reveal that the hole-sealed sample-based on ammonium fluorotitanate shows a higher corrosion resistance as compared to the one based on titanium potassium oxalate. Significantly, the optimal conditions for the hole sealing of the aluminum alloy are evidenced to be the concentration of ammonium fluorotitanate of 0.1 mol/L, AC voltage of 3 V, and time of 900 s.

Core-shell-core heterostructural engineering of Y 2 O 3 :Eu 3+ /MCM-41/YVO 4 :Eu 3+ for enhanced red emission and tunable, broadened-band response to excitation

For the first time, a hierarchical phosphor Y2O3:Eu3+/MCM-41/YVO4:Eu3+, with a core–shell-core heterostructure, is presented in this study. Synergistically bridging the phosphors Y2O3:Eu3+ (as an inner core) and YVO4:Eu3+ (as an outer core) by amorphous SiO2, i.e., MCM-41 (with ordered mesoporous channels) leads to the generation of the core–shell-core heterostructure with enhanced red emission and tunable, broadened-band response to excitation. The novel structure of the core–shell-core hierarchical material is clarified through various characterization methods including X-ray diffraction analysis, transmission electron microscopy, selected-area electron diffraction and N2 adsorption–desorption measurements. Significantly, through temperature-dependent fluorescence investigation, it is found that our core–shell phosphor (Y2O3:Eu3+/MCM-41) exhibits impressive fluorescence stability against temperature variation (27–227 °C) due to the protective effect resulting from MCM-41. By contrast, lowered stability can be noted for the core–shell-core phosphor (Y2O3:Eu3+/MCM-41/YVO4:Eu3+), especially when the temperature is higher than 100 °C, owing to the outer core (YVO4:Eu3+ nanoparticles) that is directly exposed to heat. Such a kind of luminescent materials holds substantial promise for labeling the organisms that are vulnerable to short-wavelength UV light irradiation. Additionally, potential intelligent systems can be expected to be designed on the basis of the fluorescence mutation as triggered by the temperature of 100 °C.

Design and Optimization of a New Composite Thermal Insulating Fluorocarbon Coating

Based on the mechanism of thermal insulation, a new composite fluorocarbon thermal insulation coating (FTIC) was prepared with three different fillers of closed pore perlite, hollow glass microsphere and nano-antimony tin oxide (ATO) powder, in order to get the best thermal insulation performance, the formula of the composite FTIC was optimized by varying three independent parameters (the content of closed pore perlite, hollow glass microsphere and nanoATO powder) and using a central composite design under response surface methodology. The test results show that, the temperature difference for the optimized FTIC system is 8.8°C, which is much the same to the value of 9.0°C predicated by response surface methodology model. Introduction Considering thermal insulation coating is one of the effective ways to improve building insulation properties and to reduce the energy consumption on air conditioning, we have done much in this area [1-7]; however, most researches focus on single or just two insulation mechanisms of thermal insulation combined together. In fact, the heat transfer of building is a result of combined action including obstruction, radiation and reflection. As a result, excellent thermal insulation coatings that can be used on building are still lacking in China. So, the multiple models and synergistic mechanism of thermal insulation coating system should be further studied in order to get excellent thermal insulation coatings. To meet the national needs for energy saving and emission reduction, this paper prepared a new fluorocarbon thermal insulation coating (FTIC) based on polyvinylidene fluoride emulsion. Using the principle of a central composite design under response surface methodology, this study has considered the content of three different functional fillers as the factors that could be related to thermal insulation performance of FTIC. Based on these, a new composite FTIC with multiple thermal insulation mechanism including obstruction, reflection and radiation was prepared. And the formulation of the composite FTIC was optimized by response surface methodology experiment. Experimental Methods Coating Preparation The composite fluorocarbon thermal insulation coating (FTIC) is prepared by mixing the polyvinylidene fluoride emulsion, thermal insulation functional fillers (as closed pore perlite for obstructive, hollow glass microsphere for reflective and nano-antimony tin oxide (ATO) powder for radiative coatings), solvents and additives according to a certain proportion seen in Table 1 according to our earlier work[8] and the preparation process is as shown in Fig.1. 3rd Annual International Conference on Advanced Material Engineering (AME 2017) Copyright