Construction of a floating photothermal-assisted photocatalytic system with a three-dimensional hollow porous network structure.

Solar energy is the inevitable choice to achieve the low-carbon, green, and circular development of society, and photocatalysis technology is one of the shining pearls. To make full use of the solar spectrum and solve the shortcomings of the recovery difficulty of powdery materials and the loss of activity due to the influence of the external environment, it is possible to construct floating materials using melamine sponges to recover photocatalytic materials quickly. At the same time, floating materials can absorb oxygen in the air for the generation of active groups, effectively solving the problem of less O2 in the water. The carbon-based materials have excellent light absorption properties, high thermal conductivity, and excellent photothermal conversion efficiency and are ideal for constructing floating photothermal photocatalytic systems. As an example, we combined a cheap melamine sponge with urea, prepared a hollow porous network structure g-C3N4 (HPNCN) with a high specific surface area by direct thermal shrinkage method, and then attached the CoO to its surface by hydrothermal method to form a heterojunction with a suitable band gap. Various characterization tests verified the photothermal-photocatalytic properties. Among them, 30% CoO/HPNCN has the best photocatalytic degradation effect on tetracycline (TC), and the removal rate is 88.1%. After five cycles, the removal rate is only 5% lower than the initial, indicating that it has good stability and recyclability. We conducted an active ingredient capture experiment, ESR, and LC-MS analysis to clarify the intermediates and reaction mechanism of TC photocatalytic degradation. On this basis, the ECOSAR program and QSAR method were used to analyze the environmental toxicity of TC and its intermediate products. These results provide a broad prospect for the potential application of the floating photothermal-photocatalysis system in antibiotic pollution control and its application in other fields.

Rational Design of Monolithic g-C3N4 with Floating Network Porous-like Sponge Monolithic Structure for Boosting Photocatalytic Degradation of Tetracycline under Simulated and Natural Sunlight Illumination.

In order to solve the problems of powder g-C3N4 catalysts being difficult to recycle and prone to secondary pollution, floating network porous-like sponge monolithic structure g-C3N4 (FSCN) was prepared with a one-step thermal condensation method using melamine sponge, urea, and melamine as raw materials. The phase composition, morphology, size, and chemical elements of the FSCN were studied using XRD, SEM, XPS, and UV-visible spectrophotometry. Under simulated sunlight, the removal rate for 40 mg·L-1 tetracycline (TC) by FSCN reached 76%, which was 1.2 times that of powder g-C3N4. Under natural sunlight illumination, the TC removal rate of FSCN was 70.4%, which was only 5.6% lower than that of a xenon lamp. In addition, after three repeated uses, the removal rates of the FSCN and powder g-C3N4 samples decreased by 1.7% and 2.9%, respectively, indicating that FSCN had better stability and reusability. The excellent photocatalytic activity of FSCN benefits from its three-dimensional-network sponge-like structure and outstanding light absorption properties. Finally, a possible degradation mechanism for the FSCN photocatalyst was proposed. This photocatalyst can be used as a floating catalyst for the treatment of antibiotics and other types of water pollution, providing ideas for the photocatalytic degradation of pollutants in practical applications.