Mesoporous tubular g-C3N4 as an efficient metal-free photocatalyst with peroxymonosulfate to degrade carbamazepine

In advanced oxidation processes with metal-containing catalysts, metal dissolution usually leads to reduced efficiency and biotoxicity. Therefore, it is very important to find efficient non-metallic materials. In this work, a metal-free mesoporous tubular g-C₃N₄ was fabricated using melamine and urea mixed according to the mass ratios of 1:12 (TPCN₁₂) by a facile one-step thermal polymerization method. Mesoporous tubular TPCN₁₂ was proved to be successfully synthesized by scanning electron microscope (SEM) and X-ray diffraction (XRD). Then the degradation of carbamazepine (CBZ) by activating peroxymonosulfate (PMS) of TPCN₁₂ under visible light was investigated. It was found that degradation rate constant of CBZ in TPCN₁₂/Vis/PMS system (0.0939 min⁻¹) exhibited great superiority over that in TPCN₁₂/Vis system (0.0149 min⁻¹) and in TPCN₁₂/PMS system, which indicated TPCN₁₂, Vis and PMS had a synergistic effect. The dominant role of the electron transfer and the primary contribution of the holes (h⁺) and •O₂⁻ reactive species were revealed in TPCN₁₂/Vis/ PMS system. Furthermore, the system showed sufficient advantages over a wide pH range and high resistance to inorganic anions. In general, the TPCN₁₂/Vis/PMS system was capable of high stability and recyclability. This metal-free mesoporous tubular catalyst was proposed to achieve efficient and green elimination of pharmaceutical organic pollutants.