In this work, a CdS/BiVO
4
step-scheme (S-scheme) heterojunction with self-photothermally enhanced photocatalytic effect was synthesized and applied for efficient U(VI) photoextraction. ...Characterizations such as transient absorption spectroscopy and Tafel test together confirmed the formation of S-scheme heterojunctions, which allows CdS/BiVO
4
to avoid photocorrosion while retaining the strong reducing capacity of CdS and the oxidizing capacity of BiVO
4
. Experimental results such as radical quenching experiments and electron spin resonance show that U(VI) is rapidly oxidized by photoholes/
•
OH to insoluble UO
2
(OH)
2
after being reduced to U(IV) by photoelectrons/
•
O
2
-
, which precisely avoids the depletion of electron sacrificial agents. The rapid recombination of electron-hole pairs triggered by the S-scheme heterojunction is found to release large amounts of heat and accelerate the photocatalysis. This work offers a new enhanced strategy for photocatalytic uranium extraction and presents a direction for the design and development of new photocatalysts.
Supramacromolecular hydrogels (SMHGs) are attractive materials in various areas. Due to their excellent reversible photoisomerization ability, azobenzene derivatives have been widely applied to ...construct SMHGs. But the majority of these systems were realized only by transplanting azobenzene function groups into macromolecule chains, while low-molecular-weight (LMW) azobenzene derivatives are fairly rare. Therefore, it is highly desirable to develop facile and effective strategies for the construction of SMHG. Here, a new ABA-typed azobenzene derivative (AD) has been designed and synthesized, which can be applied as LMW crosslinkers to construct SMHGs through electrostatic interactions between AD and sodium alginate (SA). When AD is mixed with SA solution in acidic conditions, SMHGs can form at various concentrations of SA. In addition, the concentration of AD also has a large impact on the moduli values. Profiting from electrostatic interactions between AD and SA, as well as interchain hydrogen bonds of SA, SMHGs can experience sol-gel transitions under pH-, photo- or thermo-stimuli. This work contributes a simple but effective strategy for the construction of SMHGs using azobenzene derivatives as LMW crosslinkers.
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•Piezocatalysis extraction of U(VI) was first achieved using minerals.•The energy band cyclically matching is proved theoretically.•Charge transfer at the interface of ...Ca(Al2Si2O8)/Fe2O3 is enhanced.•Piezocatalysis efficiency achives 96%.•The heterojunction show great potential in U(VI) extraction from seawater.
Energy and environmental issues make the generation of H2O2 and the separation of U(VI) from water very important topics. In this work, we disclosed a low-cost, high-efficiency method for separating U(VI) from water based on the naturally formed catalyst (red volcanic stone powders, RVSP) of Ca(Al2Si2O8)/Fe2O3 heterojunction through a piezocatalytic pathway induced by ultrasonication. The charges were found to be elevatedly separated due to the formation of the heterojunction. It is found that under ultrasonication, charges were effectively separated and then reacted with water to form H2O2 with a high yield of 196.7 μmol·g−1 in 4 h, which further solidifies U(VI) to form a solid of UO2O2. The removal rate of U(VI) in water reached 96 % (50 ppm) within 150 min. Furthermore, the results calculated by VASP show that the cyclic variation of the conduction bands under a cyclic force field facilitates the charge separation, and thus may promote piezocatalysis. Most importantly, the application study in real seawater indicates that U(VI) piezocatalysis based on natural minerals has great potential. This work presents a comprehensive investigation of U(VI) piezocatalysis by Ca(Al2Si2O8)/Fe2O3 and provides a new idea for piezocatalytic extraction of uranium.
Energy and environmental issues make the generation of H
O
and the separation of U(VI) from water very important topics. In this work, we disclosed a low-cost, high-efficiency method for separating ...U(VI) from water based on the naturally formed catalyst (red volcanic stone powders, RVSP) of Ca(Al
Si
O
)/Fe
O
heterojunction through a piezocatalytic pathway induced by ultrasonication. The charges were found to be elevatedly separated due to the formation of the heterojunction. It is found that under ultrasonication, charges were effectively separated and then reacted with water to form H
O
with a high yield of 196.7 μmol·g
in 4 h, which further solidifies U(VI) to form a solid of UO
O
. The removal rate of U(VI) in water reached 96 % (50 ppm) within 150 min. Furthermore, the results calculated by VASP show that the cyclic variation of the conduction bands under a cyclic force field facilitates the charge separation, and thus may promote piezocatalysis. Most importantly, the application study in real seawater indicates that U(VI) piezocatalysis based on natural minerals has great potential. This work presents a comprehensive investigation of U(VI) piezocatalysis by Ca(Al
Si
O
)/Fe
O
and provides a new idea for piezocatalytic extraction of uranium.
•The synergetic enhancement of the piezo catalysis of K2Ti6O13/TiO2 nanocomposite.•The enhancement of the piezo catalysis is due to the band gap engineering.•The mechanism of the piezo catalysis is ...systematically investigated.
The K2Ti6O13/TiO2 heterojunction is constructed to improve the piezo catalytic performance of tetracycline. Display omitted
Piezo catalysis has recently been considered an important technology in environmental treatment. In this study, a type II heterojunction of K2Ti6O13/TiO2 composite is successfully prepared by a hydrothermal method for the highly efficient piezo catalytic degradation of tetracycline. The factors influencing the piezo catalysis of tetracycline are systematically studied and discussed, including pH value, competition of anions/cations, ultrasonic power, ultrasonic frequency, and temperature, etc. Free radical sacrificial agents (EDTA-2Na, DMSO, AgNO3, and P-BQ, etc.) are utilized to better understand the degradation mechanism by piezo catalysis, and holes are found to play a dominant role in the catalytic process, and ·O2- comes the second. The combination of K2Ti6O13 and TiO2 constructs a type II heterojunction of the highly efficient separation of piezo electrons and holes, thus systematically increasing the piezo catalytic performance. This work provides a new idea to degrade organic pollution through piezo catalysis and the potential application of piezo catalysis in environmental treatment.
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•CdTe nanoparticles were obtained by a hydrothermal method.•Cr(VI) is highly efficient photo reduced to Cr(III) under the visible and infrared irradiation.•e− and h+ and OH were ...involved in the photocatalytic reduction of Cr(VI).
The utilization of near-infrared (NIR) light may greatly enlarge the application range of irradiated light of a photocatalyst, which is still an issue needing to be solved. In this work, CdTe nanoparticles are firstly found to be endowed with the capacity to photo-reduce Cr(VI) to Cr(III) under infrared light irradiation. The CdTe nanoparticles are prepared under a facile hydrothermal condition, with diameters of approximately 22 nm, which shows high photo-reduced efficiencies to Cr(VI) of 82.44% at the irradiation of a Xe lamp (500 W, including the visible light and infrared light), and 25.54% under the irradiation of infrared light, respectively. The active species of e−, h+, and OH participate in the reduction of Cr(VI), and the photogenerated e− and OH both play a critical role in the infrared light region. This study proposes a new pathway for Cr(VI) photoreduction in wastewater under visible-NIR light irradiation which shows an application potential as a photocatalyst at the infrared light range and provides new insights for pollution reduction and environmental improvement.
The reversible photoisomerization of azobenzene (Azo) has been utilized to construct supramacromolecular hydrogels (SMHGs) in which the structure can be controlled by light. However, most of these ...examples have been realized only through grafting Azo functional group onto the macromolecular chains, and low-molecular-weight Azo derivatives are relatively scarce. Here, a novel amphiphilic azobenzene derivative (APA) has been designed and synthesized, which can be used as a low-molecular-weight crosslinker to construct SMHGs via host-guest interactions between Azo and β-cyclodextrin (β-CD). APA, with two hydrophobic ends and a hydrophilic segment, can self-assemble to spherical particles in the mixed solvent of THF and H2O, and disassemble upon UV light irradiation. When APA is mixed with the solution of hyaluronic acid modified by β-CD (HA-CD), hydrogels can form at different mass fractions of HA-CD. Moreover, when the molar ratio of APA and β-CD is 0.5, the resultant hydrogel has the highest G' value. Benefiting from the host-guest interactions between Azo and β-CD, as well as the intermolecular hydrogen bonds of hyaluronic acid, hydrogels undergo both photo- and thermo-responsive sol-gel transition. The release of Rhodamine B from the hydrogel, could be controlled by UV light irradiation or high temperature. The work presented here demonstrates a simple strategy to construct photo-responsive SMHGs by Azo-derived low-molecular-weight crosslinkers.
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•A novel amphiphilic azobenzene derivative (APA) has been designed and synthesized.•APA is composed of two hydrophobic ends and a hydrophilic segment.•APA can undergo photo-responsive self-assemble and disassemble behaviors.•APA can be used as ideal low-molecular-weight crosslinkers to construct smart SMHGs.
The self-heating effect has an important influence on the performance of a catalyst, but it is seldom investigated and reported. In this study, a self-heating heterojunction composed of Bi2WO6 and ...g-C3N4 was designed and constructed by a hydrothermal method, which greatly improved the photocatalytic performance of the material for tetracycline (TC). In addition to the heterojunction effect, the heating effect of Bi2WO6 on g-C3N4 also promoted the photocatalytic performance of the composite to TC. This phenomenon was confirmed by temperature-dependent electrochemical experiments, EIS and photocurrent curves. The heating effect of Bi2WO6 effectively accelerates the generation and separation of photoelectrons and photoholes in g-C3N4 and the composites. The concept of this study provides a new strategy for the design of efficient photocatalysts.
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•A self-heating photocatalyst is designed by combination of g-C3N4 and Bi2WO6.•The photocatalytic performance to tetracycline is greatly enhanced by the heating effect of Bi2WO6 to g-C3N4.•·O2- and H+ play the major roles in the photocatalytic degradation of tetracycline.
K7NiV13O38·16H2O was found to be an efficient homogeneous catalyst in a mixture solvent of CH3CN and acetic acid for the hydroxylation of aromatics with 30% aqueous H2O2. The new catalytic system ...showed an unprecedented catalytic activity and selectivity for the hydroxylation of aromatics bearing an electron-withdrawing group. In the case of methyl benzoate, the yield of hydroxylated products reached 73%.
