First synergistic application of photocatalysis by novel graphitic carbon nitride nanomaterial and low-temperature plasma technology for highly efficient removal of pharmaceuticals from real wastewater

This study investigates, for the first time, the combined application of visible-light photocatalysis using a novel graphitic carbon nitride (gCN) nanomaterial and low-temperature plasma generated in air by a multi-hollow surface dielectric barrier discharge (MSDBD) for the treatment of real wastewater effluent. The combined photocatalysis+plasma process exhibited high performance for a broad range of pharmaceutical compounds, with efficiencies that nearly achieved or exceeded the 80% removal threshold defined by the new EU Urban Wastewater Treatment Directive 2024/3019 (EU UWWTD 2024/3019). Analysis of reactive oxygen species (ROS) demonstrated that the pollutant degradation in the combined photocatalysis+plasma system was primarily driven by plasma-generated species, such as ozone (O 3 ), nitrates (NO 3 − ), and nitrites (NO 2 − ), whereas the contributions of superoxide anion radical (O 2 -· ) and singlet oxygen ( 1 O 2 ) generated by plasma and photocatalysis individually were minor. Fixation of ammonia in wastewater treated by MSDBD was not detected. The presence of gCN mitigated plasma-induced acidification, maintaining the wastewater pH near neutral. Investigation of the sulfamethoxazole (SMX) degradation pathway revealed an approximately 50% reduction in N4-acetyl-sulfamethoxazole, indicating partial mitigation of this persistent transformation product of environmental concern and underscoring the advantages of the combined plasma+photocatalytic process.