Z-scheme photo-Fenton catalysts of n-n g-C3N4/FeMnO3/EP for enhanced tetracycline degradation in pharmaceutical wastewater

Abstract

Tetracycline (TC) is an environmental threat due to its widespread use in the pharmaceutical industry. An n-n g-C₃N₄/FeMnO₃/EP Z-scheme autotrophic photofenton material was synthesized and subjected to TC degradation experiments. The homogeneous heterojunction modification was carried out for the carbon nitride precursor using direct heat shrinkage to effectively separate the electron-hole pairs, which was compounded with FeMnO₃ under ultrasound. The introduction of Fe/Mn bi-ionic synergistic system promotes the cyclic conversion of Fe(II)/Fe(III), which reduces the formation of iron sludge during the degradation process. The material was combined with expanded perlite for the purpose of overcoming the loss of solar energy due to water absorption and reflection in the photofenton system. The photo-Fenton performance was characterized by the combination of Potassium peroxymonosulfate (PMS) and the degradation rate was as high as 0.02741 min⁻¹. Using free radical scavenging experiments, EPR determined that SO₄^·-,·OH, ¹O₂, and ·O₂⁻ is the main active substance in the photofenton process. UV, XPS and LC-MS were used to trace the mechanism of photo-Fenton degradation of TC and possible pathways that may occur in the resulting process. The present study proposes novel theoretical concepts pertaining to the purification of TC in water and the generation of low-iron sludge in the photofenton process.