RESUMO
BiVO4 has been widely used in the field of photocatalysis due to its nontoxic and moderate band gap. However, single BiVO4 has the disadvantages of a high recombination rate of photogenerated carriers and weak response to visible light, inhibiting its photocatalytic applications. To explore viable solutions, a hybrid material composed of lanthanum-doped bismuth vanadate (La-BiVO4) and oxygen-doped porous graphite carbon nitride (O-doped g-C3N4), i.e., La-BiVO4/O-doped g-C3N4 powder, was prepared by a facile hydrothermal reaction and low-temperature calcination. Then, the powder was loaded on polyacrylonitrile nanofibers (NFs) through the electrospinning fiber technique. Various surface science characterizations, including transmission electron microscopy and nitrogen absorption and desorption analysis, confirmed the successful synthesis of a mesoporous heterojunction material. The La3+-doping as well as the porous morphologies and larger specific surface area of the O-doped g-C3N4 ultimately improve the photocatalytic abilities via a proposed Z-scheme heterojunction mechanism. The roles of La3+-doping and morphology modification in promoting the separation of the photogenerated carriers and broadening the optical absorption range were experimentally discussed. The RhB degradation experiment indicated that the La-BiVO4/O-doped g-C3N4 powder has excellent photocatalytic activity, which is about 2.85 and 2 times higher than that of the pure BiVO4 and O-doped g-C3N4, respectively. Meanwhile, the La-BiVO4/O-doped g-C3N4 NF shows good stability and recoverability after a 10-cycle testing. Such a hybrid photocatalyst with a proposed Z-scheme heterojunction mechanism and good plasticity might pave a feasible way to fabricate a new library of photocatalysts.
RESUMO
Aflatoxin B1 (AFB1) is a highly toxic mycotoxin produced by aspergillus species under specific conditions as secondary metabolites. In this study, types of PCL (Polycaprolactone) membranes anchored (or not) to g-C3N4/CQDs composites were prepared using electrospinning technology with (or without) the following surface modification treatment to remove AFB1. These membranes and g-C3N4/CQDs composites were characterized by SEM, TEM, UV-vis, XRD, XPS and FTIR to analyze their physical and chemical properties. Among them, the modified PCL-g-C3N4/CQDs electrospun membranes exhibited an excellent ability to degrade AFB1 via synergistic effects of adsorption and photocatalysis, and the degradation rate of 0.5 µg/mL AFB1 solution was observed to be up to 96.88% in 30 min under visible light irradiation. Moreover, the modified PCL-g-C3N4/CQDs electrospun membranes could be removed directly after the reaction process without centrifugal or magnetic separation, and the regeneration was a green approach synchronized with the reaction under visible light avoiding physical or chemical treatment. The mechanism of adsorption by electrostatic attraction and hydrogen bonding interaction was revealed and the mechanism of photodegradation of AFB1 was also proposed based on active species trapping experiments. This study illuminated the highly synergic adsorption and photocatalytic AFB1 removal efficiency without side effects from the modified PCL-g-C3N4/CQDs electrospun membranes, thereby offering a continual and green solution to AFB1 removal in practical application.
Assuntos
Luz , Adsorção , Catálise , FotóliseRESUMO
The degradation of aflatoxin (AF) is a topic that always exists along with the food and feed industry. Photocatalytic degradation as an advanced oxidation technology has many benefits, including complete inorganic degradation, no secondary contamination, ease of activity under moderate conditions, and low cost compared with traditional physical, chemical, and biological strategies. However, photocatalysts are usually dispersed during photocatalytic reactions, resulting in energy and time consumption in the separation process. There is even a potential secondary pollution problem from the perspective of food safety. In this regard, three electrospun membranes anchored with g-C3N4/MoS2 composites were prepared for highly efficient photocatalytic degradation of aflatoxin B1 (AFB1) under visible light. These photocatalytic membranes were characterized by XRD, SEM, TEM, FTIR, and XPS. The factors influencing the degradation efficiency of AFB1, including pH values and initial concentrations, were also probed. The three kinds of photocatalytic membranes all exhibited excellent ability to degrade AFB1. Among them, the photocatalytic degradation efficiency of the photocatalytic membranes prepared by the coaxial methods reached 96.8%. The experiment is with an initial concentration of 0.5 µg/mL (500 PPb) after 60 min under visible light irradiation. The mechanism of degradation of AFB1 was also proposed based on active species trapping experiments. Moreover, the prepared photocatalytic membranes exhibited excellent photocatalytic activity even after five-fold use in the degradation of AFB1. These studies showed that electrospun membranes anchored with g-C3N4/MoS2 composites have a high photocatalytic ability which is easily removed from the reacted medium for reuse. Thereby, our study offers a highly effective, economical, and green solution for AFB1 degradation in the foodstuff for practical application.
