Iron-doped g-C3N4 modified CoMoO4 as an efficient heterogeneous catalyst to activate peroxymonosulfate for degradation of organic dye

MoS2/CoMoO4 composite heterogeneous catalyst towards enhanced activation of peroxymonosulfate for the efficient degradation of tetracycline hydrochloride

In this research, a composite catalyst of MoS2-modified CoMoO4 (MoS2/CoMoO4) was effectively synthesized and utilized to activate peroxymonosulfate (PMS) for the removal of tetracycline hydrochloride (TCH) in water. It was found that the MoS2/CoMoO4/PMS system possessed a greater ability to eliminate TCH compared with CoMoO4/PMS system. The experimental results demonstrated that the 0.6-MoS2/CoMoO4/PMS system eliminated 92.1% TCH (15 mg/L) and removed 50.3% TOC within 30 min under the conditions of 40 mg/L 0.6-MoS2/CoMoO4 and 0.5 mM PMS. The main active substances produced by MoS2/CoMoO4 activated PMS were sulfate radicals (SO4•-), hydroxyl radicals (•OH), singlet oxygen (1O2), and superoxide radicals (O2•-), as determined by scavenging experiments and EPR analyses. Probable catalytic mechanism of 0.6-MoS2/CoMoO4 for activating PMS was proposed from two aspects: one is the synergy of Co3+/Co2+ and Mo6+/Mo4+ cycles in 0.6-MoS2/CoMoO4/PMS system; on the other hand, the low valence molybdenum and sulfur promoted the Co3+/Co2+ redox recycle during PMS activation. After four reuses, the removal performance of TCH still reached 85.1%, and the crystal structure and the element compositions of the catalyst did not alter, implying that 0.6-MoS2/CoMoO4 composite had good reusability. Thus,0.6-MoS2/CoMoO4 composite has broad application prospects in removing organic contaminants.

Non-radical-dominated catalytic degradation of methylene blue by magnetic CoMoO4/CoFe2O4 composite peroxymonosulfate activators

In this study, magnetic CoMoO₄/CoFe₂O₄ (CMO/CFO) nanospheres with a core-shell structure were synthesized via two-step hydrothermal methods. The obtained particles were employed as catalysts to activate peroxymonosulfate (PMS) and degrade methylene blue (MB). The physico-chemical characterizations of the synthesized CMO/CFO showed that the CMO shell contributed to the enhancement of redox conversion and the increase in the concentration of oxygen vacancies (OVs). By examining reactive oxygen species (ROS) in the CMO/CFO/PMS system, the MB degradation was dominated by a non-radical pathway, and ¹O₂ was identified as the most abundant ROS. Besides, the CMO/CFO exhibited faster reaction kinetics than the pristine CFO. Moreover, the magnetic properties guaranteed the recycling and reuse of CMO/CFO, and the removal rate of MB was maintained at ∼94% after continuous use five times. Both the tolerance to SO₄^2-and the wide pH range where the material is applicable make it a promising catalyst for dyeing wastewater treatment.