Enhanced Redox Cycle of Rod-Shaped MIL-88A/SnFe2O4@MXene Sheets for Fenton-like Degradation of Congo Red: Optimization and Mechanism

Abstract

This study intended to fabricate a novel Fenton-like catalyst by supporting the rod-like MIL-88A and the magnetic tin ferrite nanoparticles (SnFe₂O₄) on the MXene sheets (MIL-88A/SnFe₂O₄@MXene). The well fabrication and determination of the MIL-88A/SnFe₂O₄@MXene properties were investigated using SEM, XPS, VSM, Zeta potential, XRD, and FTIR tools. The Fenton-like degradation reaction of CR by MIL-88A/SnFe₂O₄@MXene was thoroughly studied to identify the optimal proportions of the catalyst components, the impact of CR and H₂O₂ concentrations, as well as the effect of raising the temperature and the pH medium of the catalytic system and the catalyst dosage. Kinetics studies were executed to analyze the decomposition of CR and H₂O₂ using First-order and Second-order models. Furthermore, the degradation mechanism was proposed based on the scavenging test that proceeded in the presence of chloroform and t-butanol, in addition to the XPS analysis that clarified the participation of the containing metal species: Fe, Sn, and Ti, and the formation of a continual redox cycle. The obtained intermediates during the CR degradation were defined by GC-MS. A recyclability test was performed on MIL-88A/SnFe₂O₄@MXene during five runs of the Fenton-like degradation of CR molecules. Finally, the novel MIL-88A/SnFe₂O₄@MXene Fenton-like catalyst could be recommended as a propitious heterogeneous catalyst with a continuous redox cycle and a recyclability merit.

Keywords: Fenton-like reaction; MXene; mechanism; redox reactions; synergistic effect.

Scheme 1

The fabrication procedure of the MIL-88A/SnFe₂O₄@MXene catalyst.

Figure 1

(a) FTIR, (b) XRD, (c) VSM, and (d) Zeta potential of the magnetic MIL-88A/SnFe₂O₄@MXene and its authentic components.

Figure 2

SEM images of (a) MIL-88A, (b) SnFe₂O₄, (c) MXene, and (d) MIL-88A/SnFe₂O₄@MXene composite.

Figure 3

XPS analysis of MIL-88A/SnFe₂O₄@MXene; (a) Survey, (b) Ti2p, (c) Fe2p, (d) Sn3d, (e) C1s, (f) O1s, and (g) F1s.

Figure 4

(a) The catalytic degradation of CR using various catalysts (CR concentration = 50 mg/L, catalyst mass = 10 mg, pH = 3, H₂O₂ concentration = 100 mg/L, t = 30 min, and temperature = 20 °C), (b) Effect of the pH medium (CR concentration = 50 mg/L, catalyst mass = 10 mg, pH = 3–11, H₂O₂ concentration = 100 mg/L, t = 30 min, and temperature = 20 °C), and (c) Effect of H₂O₂ concentration (CR concentration = 50 mg/L, catalyst mass = 10 mg, pH = 3, H₂O₂ concentration = 10–200 mg/L, t = 30 min, and temperature = 20 °C).

Figure 5

(a) Effect of catalyst dose (CR concentration = 50 mg/L, catalyst mass = 5–20 mg, pH = 3, H₂O₂ concentration = 100 mg/L, t = 30 min, and temperature = 20 °C), (b) Effect of the reaction temperature (CR concentration = 50 mg/L, catalyst mass = 10 mg, pH = 3, H₂O₂ concentration = 100 mg/L, t = 30 min, and temperature = 20–50 °C), (c) Effect of the CR concentrations (CR concentration = 50–300 mg/L, catalyst mass = 10 mg, pH = 3, H₂O₂ concentration = 100 mg/L, t = 70 min, and temperature = 20 °C), and (d) H₂O₂ decomposition (CR concentration = 50 mg/L, catalyst mass = 10 mg, pH = 3, H₂O₂ concentration = 100 mg/L, t = 60 min, and temperature = 20 °C).

Figure 6

(a) First-order, (b) Second-order of the Fenton-like degradation of CR, (c) First-order and (d) Second-order of H₂O₂ decomposition by MIL-88A/SnFe₂O₄@MXene catalyst.

Figure 7

(a) Scavenging test, (b) XPS survey of the used MIL-88A/SnFe₂O₄@MXene, (c) Fe2P spectrum, (d) Sn3d spectrum, and (e) Ti2p spectrum.

Figure 8

The adsorption and Fenton-like degradation of CR by MIL-88A/SnFe₂O₄@MXene.

Figure 9

Proposed degradation mechanism of CR molecules based on GC–MS analysis.

Figure 10

Recyclability test of MIL-88A/SnFe₂O₄@MXene during five runs of the Fenton-like degradation reaction of CR molecules.