Enhanced activation of peroxymonosulfate by bimetallic spinel sulfides CoNi2S4 for organic dye degradation

The activation of peroxymonosulfate (PMS) with bimetallic spinel sulfides to degrade refractory organic pollutants is a promising method. In this work, a one-step hydrothermal method was used to synthesize high catalytic activity CoNi 2 S 4 . Catalyst CoNi 2 S 4 was characterized by X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FT-IR) and field-emission scanning electron microscopy (SEM). Subsequently, CoNi 2 S 4 was applied to activate PMS for Rhodamine B (RhB) degradation. After 50 mins of catalytic reaction , the removal rate of RhB (20 mg/L) reached 99.1% and the removal rate of COD reached 60.0% in the CoNi 2 S 4 (150 mg/L) + PMS (150 mg/L) system at room temperature of 20 ℃. The experiment results showed that the CoNi 2 S 4 had preeminent catalytic activity. The singlet oxygen ( 1 O 2 ) and sulfate radical (SO 4 •− ) were proved to perform critical roles in the catalytic degradation process by electron paramagnetic resonance (EPR) analysis and quenching experiment. Meantime, the potential catalytic mechanism of PMS activation by CoNi 2 S 4 was proposed mainly in two aspects: one is that S 2 2- and S 2- species promote the Co 3+ /Co 2+ and Ni 3+ /Ni 2+ cycles on CoNi 2 S 4 surface, and the other is that there is the synergistic effect of Co-Ni cycles for PMS activation by CoNi 2 S 4 . Recycling tests showed that the degradation efficiency of RhB was stable, indicating that CoNi 2 S 4 had good recyclability . Because of its outstanding catalytic activity, easy preparation, and reusability, the CoNi 2 S 4 catalyst has broad application prospects in the field of controlling water pollution .