Environmental geopolymer microsphere composite catalysts as highly efficient activators of peroxymonosulfate (PMS) for the degradation of Rhodamine B

As efficient activators of peroxymonosulfate (PMS), cobalt ions play an important role in the degradation of organic pollutants. It is imperative to synthesize PMS activators from low-cost materials with uniform structures to improve the catalytic efficiency and cycle life and reduce the cost of wastewater treatment, which has practical importance. In this work, alkali-activated slag geopolymer microsphere-supported Co catalysts (Co-GMs) were synthesized via a simple solution impregnation method and used for the degradation of Rhodamine B (RhB). The Co-GM/PMS system is highly efficient, and the degradation rate of RhB (40 mg/L) reached 99.8% within only 10 min. Moreover, Co-GM has a wide pH range from 3 to 9 and good anti-interference performance for other ions, as well as low Co²⁺ leaching (0.809 mg/L) and favorable reusability. Reactive oxygen species (ROS) were explored via radical quenching experiments and electron spin-resonance (ESR) spectroscopy, which revealed determined that the major ROS involved in the degradation of RhB are ¹O₂ and SO₄^·−. The synergistic effect of free and nonfree radicals plays an important role during degradation. Moreover, four probable degradation pathways were proposed via liquid‒phase mass spectrometry (LC‒MS). The results revealed that the removal rate of total organic carbon (TOC) reached 74.2% within 60 min. This research innovatively proposed the application of geopolymer composite catalysts in advanced oxidation and developed an ultralow-cost PMS activator for highly efficient degradation of RhB, which represents a new choice for wastewater treatment.

Graphical abstract