Synergistic design of CuO/CoFe₂O₄/MWCNTs ternary nanocomposite for enhanced photocatalytic degradation of tetracycline under visible light

Abstract

This study involves a novel CuO/CoFe₂O₄/MWCNTs (CCT) nanocomposite, developed by integrating cobalt ferrite (CoFe₂O₄) and copper oxide (CuO) nanoparticles onto multi-walled carbon nanotubes (MWCNTs), for the degradation of tetracycline (TC) under visible light. The photocatalyst was extensively characterized using XRD, HR-SEM, EDX, HR-TEM, UV-Vis, BET, and PL analysis. The synthesized CoFe₂O₄ and CuO nanoparticles exhibited crystallite sizes of 46.8 nm and 37.5 nm, respectively, while the CCT nanocomposite had a crystallite size of 53 nm. Microscopy confirmed a particle size of 49.2 nm for the nanocomposite, with MWCNTs measuring 15.65 nm in diameter. The band gap energy of the CCT nanocomposite was 1.6 eV, which contributed to its enhanced photocatalytic activity, as evidenced by the lower emission intensity in PL analysis. BET analysis revealed a pore volume of 0.37 cc/g and a surface area of 82.3 m²/g. Photocatalytic performance was tested across various conditions, with adjustments to nanocomposite dosages (0.1-0.5 g/L), TC concentrations (5-25 mg/L), and pH levels (2-10). Under optimized conditions (0.3 g/L CCT, 5 mg/L TC, pH 10, 120 min of visible light exposure), the CCT achieved 98.1% degradation of TC. The optimized parameters were subsequently used to assess TC degradation with individual photocatalysts: CoFe₂O₄, CuO, CT, and CCT. The enhanced photocatalytic efficiency observed can be largely attributed to the improved charge transfer dynamics and effective electron-hole separation facilitated by MWCNT doping. The reaction followed a pseudo-first-order kinetic model, with hydroxyl radicals (OH^•) identified as the key species in the degradation process. Moreover, the catalyst exhibited 96% retention of its photocatalytic efficiency after five consecutive cycles, demonstrating exceptional stability and reusability. These results emphasize the CCT composite's potential as a highly efficient and sustainable photocatalyst for the remediation of pharmaceutical pollutants in aquatic systems.

Keywords: CuO/CoFe2O4/MWCNTs; Degradation kinetics; Photocatalysis; Tetracycline; Visible light.

Fig. 1

Acidic dissociation constants (pK_a) of TC structure.

Fig. 2

Illustrate detailed synthesis procedures for CCT nanocomposite.

Fig. 3

XRD spectra of (a) MWCNTs (b) CoFe₂O₄, (c) CuO, (d) CT, and (e) CCT.

Fig. 4

HR-SEM images of (a) CoFe₂O₄, (b) MWCNTs, (c) CT, and (d) CCT nanocomposites.

Fig. 5

EDX analysis of (a) CoFe₂O₄, (b) MWCNTs, (c) CT, and (d) CCT nanocomposites.

Fig. 6

HR-TEM images of (a) CoFe₂O₄, (b) MWCNTs, (c) CT, and (d) CCT nanocomposites.

Fig. 7

UV-Vis spectra of (a) CoFe₂O₄, (b) CuO, (c) CT, and (d) CCT nanocomposites.

Fig. 8

BET analysis of (a) CoFe₂O₄, (b) MWCNTs, (c) CT, and (d) CCT nanocomposites.

Fig. 9

PL spectra of synthesized materials at room temperature.

Fig. 10

(a) Impact on the percentage of TC degradation by various catalyst dosages, (b) Bar diagram of TC removal at various CCT dosages, (c) Effect of concentration ratios on TC degradation using CCT nanocomposite dosages, and d) UV-Vis spectra of TC antibiotic degradation by 0.3 g/L of CCT nanocomposite.

Fig. 11

(a) Concentration effects of antibiotics on the degradation process, (b) Bar diagram of TC removal at different concentrations by 0.3 g/L of CCT composite, (c) Effect of concentration ratios with various TC concentrations, and (d) UV-Vis spectra of TC antibiotics of 5 mg/L.

Fig. 12

(a) The effect of pH on the degradation of TC using CCT nanocomposite, (b) Bar diagram of TC removal at different pH values, (c) The effect of concentration ratios in different pH of the solution, and d) UV-Vis spectra of TC antibiotics of the solution at pH = 10.

Fig. 13

(a) Impact on degradation efficiency of pure and composite (b) Bar chart of TC degradation efficiency (c) Effect of catalysts on dark adsorption.

Fig. 14

(a) Pseudo-first-order kinetic plots for different concentrations of antibiotics. (b) Bar graph showing rate constants and associated error values for different concentrations.

Fig. 15

(a) Impact on the relative concentration of TC degradation in each cycle (b) Bar diagram of TC degradation efficiency in each cycle (c) XRD spectra and d) HR-TEM of CCT nanocomposite before and after degradation.

Fig. 16

The effect of scavengers (IPA, AO, and CH) on TC degradation.

Fig. 17

Mechanism of photocatalytic degradation using CCT nanocomposite.