The widespread use of tetracycline (TC), a common antibiotic, has unfortunately led to its accumulation in water systems, posing significant environmental and health concerns. Traditional water treatment methods often fall short in completely eliminating TC. However, advanced oxidation processes, particularly photocatalytic technologies, show great promise in addressing this issue by harnessing solar energy to degrade pollutants. In a recent study published in RSC Advances by Qi Wei, Baojun Yi, Zewen Hua, Zhengshuai Sun, and Feng Guo, researchers explored innovative photocatalyst combinations to enhance TC degradation in water.

The study focused on developing high-performance photocatalysts by synergistically integrating biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More (BC), carbon nitride (CN), and covalent organic frameworks (COF). Heterojunctions, which are interfaces between two different semiconductor materials, are crucial in photocatalysis because they improve the separation of light-generated electron-hole pairs, thereby boosting efficiency. This research delves into the creation of novel heterojunctions, with a particular emphasis on using cost-effective biochar as an electron mediator to overcome the limitations of traditional, more expensive mediators like heavy metals or carbon nanotubes.

The researchers synthesized various combinations of these materials and meticulously characterized their properties, including morphological, structural, and optical features. They found that the binary photocatalyst, demonstrated a significantly improved TC degradation efficiency, outperforming individual CN-10 and COF-2 by factors of 2.02 and 1.96, respectively, reaching a remarkable 99.79% degradation rate after 360 minutes of photoreaction. This enhanced performance is attributed to the effective π-electron delocalization facilitated by the 2D/2D heterojunction formed between the CN and COF layers, which improves Z-scheme charge transfer efficiency.

Building on this, the study further introduced biochar to create ternary photocatalysts. The all-solid-state Z-scheme heterojunction photocatalyst in which biochar acts as an electron mediator, achieved a substantial 3.13-fold increase in TC degradation. This impressive enhancement resulted in a TC degradation rate of 99.65 %. This highlights the specific pathway through which these novel photocatalysts operate. The research also revealed that the sequence of chemical compounding steps during synthesis significantly influences photocatalytic performance, with chemical compounding at the final stage notably enhancing overall performance.

This study successfully demonstrates a novel and effective approach for the photocatalytic degradation of tetracycline. By combining the unique properties of carbon nitride and covalent organic frameworks with the cost-effectiveness and electron-mediating capabilities of biochar, the developed all-solid-state Z-scheme heterojunction photocatalyst offers a promising solution for environmental remediation efforts, particularly in addressing antibiotic contamination in water.

Source: Wei, Q., Yi, B., Hua, Z., Sun, Z., & Guo, F. (2025). Biochar-mediated carbon nitride and covalent organic framework photocatalyst for enhanced tetracycline degradation. RSC Advances, 15(17491), 17491–17502.