N-doped carbon intercalated Fe-doped MoS2 nanosheets with widened interlayer spacing: An efficient peroxymonosulfate activator for high-salinity organic wastewater treatment

Abstract

Peroxymonosulfate (PMS) heterogeneous catalysis dominated by nonradical pathway showed excellent adaptability for pollutant removal in complex water matrixes. Herein, ultra-small Fe-doped MoS₂ nanosheets with N-doped carbon intercalation (CF-MoS₂) were synthesized via a one-step hydrothermal method to treat high salinity organic wastewater. CF-MoS₂ exhibited an expanded interlayer spacing by 1.63 times and the specific surface area by 9 times compared with Fe-doped MoS₂ (F-MoS₂), substantially increasing the active sites. Homogeneous Fe²⁺ catalytic experiments confirmed that the promotion of carbon intercalated MoS₂ (C-MoS₂) on Fe³⁺/Fe²⁺ redox cycle was much higher than pure MoS₂. Besides, the considerable removal of tetracycline (TC) under high salinity conditions (0-7.1%) was attributed to the dominant role of PMS nonradical oxidation pathways, including ¹O₂ and surface-bound radicals. The catalytic sites included Fe³⁺/Fe²⁺, Mo⁴⁺/Mo⁵⁺/Mo⁶⁺, C=O, pyridine N, pyrrolic N and hydroxyl groups. Finally, density functional theory (DFT) was employed to get the radical electrophilic attack sites and nucleophile attack sites of TC, and the results were consistent with the TC degradation products determined by HPLC-MS. This work would broaden the application of MoS₂-based catalysts, especially for PMS catalytic removal of organic pollutants from high salinity wastewater.

Keywords: Fe(3+)/Fe(2+) redox cycle; High salinity wastewater; Molybdenum disulfide; N-doped carbon intercalation; Peroxymonosulfate; Tetracycline; Widened interlayer spacing.