Straw-Derived Activated Carbon Decorated with Ag3PO4 for Organic Pollutant Removal by a Circular Degradation Mechanism: Adsorption and Photocatalysis

The escalating problem of water pollution has become an urgent concern, as it significantly undermines people's quality of life and overall public health. The increasing severity of water pollution represents a global challenge, with profound implications for human society. In this study, hydrothermal carbonization coupled with alkaline activation was utilized to repurpose barley straw into activated carbon (AC) as an absorbent. Silver phosphate (Ag3PO4) was synthesized as a potent photocatalyst. Subsequent ultrasound-assisted loading integrated the robust adsorptive capabilities of the AC with the advanced photocatalytic efficiency of silver phosphate, resulting in a superior composite material (AC/Ag3PO4) and implementing a novel "absorption-photocatalysis" active circular degradation strategy to remove hazardous organics in water. Comprehensive characterization assays confirmed the successful synthesis and incorporation of Ag3PO4 onto the AC scaffold. The composite with a Ag3PO4 concentration of 3 wt % exhibited a high methylene blue (MB) removal efficiency of 99.4% within 100 min. The reaction rate of this composite surpassed that of standalone AC by a factor of 2.89. Furthermore, cyclic regeneration studies via adsorption-desorption methodologies revealed the composite's resilience and sustained performance. The MB removal efficiency was maintained at 85.5% over five consecutive cycles, demonstrating the composite's remarkable stability. The integration of adsorptive and photocatalytic functionalities within a single system mitigates potential secondary pollution arising during the AC's desorption phase and enhances the organic contaminant removal efficiency. Moreover, the utilization of this integrated material reduces the quantity of chemicals and energy required for conventional adsorption water treatment techniques, as the material harnesses sunlight or alternative light sources to catalyze contaminant decomposition. This reduces the dependence on chemical treatment agents, contributing to resource conservation and alleviating environmental burdens. This pioneering approach offers a novel paradigm for addressing pollutant challenges in aqueous environments.

Photocatalytic Hydrogen and Oxygen Evolution Performed by a Long-Afterglow Material

A micron-sized long-afterglow material, Sr2MgSi2O7:Eu,Ce, was utilized to conduct the hydrogen evolution reaction and oxygen evolution reaction, two half-reactions of water splitting, in the presence of sacrificial agents under both light and dark conditions for the first time. The as-synthesized Sr2MgSi2O7:Eu,Ce exhibited higher photocatalytic activity compared to that of the referenced Sr2MgSi2O7:Eu and Sr2MgSi2O7:Ce samples. Herein, in addition to benefiting from the long photogenerated carrier lifetime of long-afterglow materials, the higher photocatalytic activity was attributed to the conjugated electronic structure between Eu and Ce ions. This structure facilitates charge and energy transfer between them, leading to an enhanced photocatalytic efficiency. This research provides a new strategy for designing efficient long-afterglow material photocatalysts through the construction of conjugated electronic structures.

Review on long afterglow nanophosphors, their mechanism and its application in round-the-clock working photocatalysis

Semiconductor assisted photocatalysis is one of the most efficient methods for the degradation of complex organic dyes. A major limiting factor of semiconductor assisted photocatalysis is the requirement of a continuous source of light to perform a redox reaction. One of the upcoming solutions is photon energy-storing long afterglow/persistent phosphors. They are an unusual kind of rechargeable, photon energy capturing/trapping phosphors that can trap charge carriers (electrons/holes) in their meta-stable energy levels, thereby resulting in persistent luminescence. Persistence luminescence from such materials can range from minutes to hours. The coupling of long afterglow phosphors (LAP) with the conventional semiconductor is a promising way to support the photocatalytic process even in dark. In addition, dissimilar band structures of LAPs and semiconductor results in formation of heterojunction which further suppresses the recombination of charge. Such an encouraging idea of LAP for round-the-clock working photocatalytic system is in its premature stage; which is required to be investigated fully. Thus, we present a state-of-art review on the potential materials for assisting round-the-clock photocatalysis, trapping-detrapping mechanism in LAP materials, fabrication strategies and their associated characterization tools. Review also covers LAP materials and their photocatalytic mechanism briefly.

Concerted catalytic and photocatalytic degradation of organic pollutants over CuS/g-C3N4 catalysts under light and dark conditions

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CuS/g-C₃N₄ composite catalysts were successfully fabricated.

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The optimal mass ratio of CuS in the composite was determined.

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Fenton-like catalytic and photocatalytic effects were combined for sewage purification.

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The continuous degradation of organic pollutants was achieved.

Organic pollutants in industrial and agricultural sewage are a serious threat to the environment and human health. Achieving continuous photocatalytic degradation of organic pollutants under light and dark conditions would have exciting implications for practical sewage treatment. In this paper, CuS/g-C₃N₄ composite catalysts with CuS nanoparticles anchored on g-C₃N₄ sheets were successfully fabricated via a simple solvothermal reaction. The morphology, structure, optical absorption characteristics, electron–hole recombination rate, and degradation performance of the as-prepared CuS/g-C₃N₄ catalysts were investigated in detail. The results confirmed that the as-fabricated CuS/g-C₃N₄ catalysts exhibited high Fenton-like catalytic degradation efficiencies in the dark, and rapid concerted Fenton-like catalytic, direct H₂O₂ photocatalytic and CuS/g-C₃N₄ photocatalytic degradation activities under visible light. Thus, the as-fabricated CuS/g-C₃N₄ catalysts can degrade organic pollutants continuously during both day and night. These degradation properties, along with the simple catalyst fabrication process, will facilitate the practical application of this system in the continuous removal of organic pollutants.