CuO/g-C3N4 Nanocomposites for Enhanced Glyphosate Degradation: The Vital Role of High-Valent Copper

Fenton-like reactions involving semiconductors and metal-based compounds have been widely reported for wastewater treatment. However, there are still some unknown areas that need to be explored, such as the degradation mechanism, the toxicity of the composite system, and active species. In this article, a series of CuO/g-C₃N₄ nanocomposites were synthesized via calcination of a mixture of cupric sulfate (CuSO₄·5H₂O) and melamine. The construction and morphology of CuO/g-C₃N₄ nanocomposites were characterized at length. In the presence of hydrogen peroxide (H₂O₂), the catalytic capability of CuO/g-C₃N₄ for glyphosate degradation was investigated. Our research showed that CuO/g-C₃N₄ nanocomposites exhibited excellent catalytic performance for the removal of glyphosate within a wide pH scope (3.48–9.69), a high mineralization rate (68.1%), and a superior degradation rate (99.3%). This work revealed that high-valent copper (Cu(III)), rather than the hydroxyl radical (^•OH), played a major role in glyphosate removal. In addition, seed germination experiments confirmed that the biotoxicity of glyphosate to wheat seeds was greatly reduced after degradation via the CuO/g-C₃N₄/H₂O₂ system. This study suggests that CuO/g-C₃N₄/H₂O₂ can be a promising candidate for efficiently removing glyphosate from wastewater.