Ruthenium confined within hollow spherical carbon nitride as an efficient catalyst for triggering peroxymonosulfate

Abstract

Acetaminophen (ACT) has been extensively used nowadays as an effective drug for treating fever and pain, but refractory ACT released into aquatic environments can hardly be eliminated by ordinary approaches, causing a serious threat to the ecological environment. Herein, a new catalyst of metallic Ru confined within porous hollow spherical carbon nitride (Ru-hsCN) was fabricated for triggering peroxymonosulfate (PMS) and then degrading ACT in solutions. In the Ru-hsCN catalyst, highly dispersed Ru species were immobilized on the hsCN matrix by forming Ru–N bonds. The catalyst of 0.34Ru-hsCN with optimal Ru loading completely removed ACT within 5 min via PMS activation, and the reaction rate reached up to 0.497 min⁻¹. The contrast sample of 0.34Ru-hsCN-imp with Ru aggregation only showed 34.4% of ACT removal in 20 min. It was worth noting that the rate constant of 0.34Ru-hsCN was 18 times higher than that of 0.34Ru-hsCN-imp (0.027 min⁻¹) in the PMS induced ACT degradation. In addition, the 0.34Ru-hsCN/PMS system showed a wide pH working range, satisfactory durability and good tolerance to inorganic anions and cations, where Cl⁻ had a significantly positive effect. Further investigations unveiled that the reactive oxygen species including SO₄˙⁻, OH, O₂˙⁻ and ¹O₂ were produced in the 0.34Ru-hsCN/PMS system, and singlet oxygen (¹O₂) was the predominant species which actuated ACT degradation.