Solar light-responsive g-C₃N₄ and Ni₁₋ₓMnₓCo₂₋ᵧFeᵧO₄ composites for rapid dye degradation and phytotoxicity evaluation

A series of Ni 1-x Mn x Co 2-y Fe y O 4 /g-C 3 N 4 composites were prepared by co-precipitation and ultra-sonication approaches and the effect of Mn and Fe substitution and g-C 3 N 4 addition was explored based on structural, dielectric, ferroelectric, optical and photocatalytic properties. The X-ray diffraction analysis confirmed the formation of a cubic structure with a particle size range of 28-35 nm of cobaltites (spinel structure). The grain size enhancement through Mn and Fe substitution was observed and the dielectric constant decreased as the frequency increased. The tangent loss was used to measure the energy loss in dielectric relaxation. The P-E loop shows enhanced coercivity (12.25 kV/cm), saturation polarization (7.72×10 -3 Ps (μC/cm 2 ) and remnant polarization (7.6×10 -3 μC/cm 2 ) for highly substituted nanocomposite. The PL analysis revealed the low recombination rate of h + -e - and bandgap declined from 1.62-1.16 eV for highly substituted NiCo 2 O 4 /g-C 3 N 4 nanocomposite. Crystal violet dye was degraded under solar light exposure and Ni 1-x Mn x Co 2-y Fe y O 4 /g-C 3 N 4 exhibited a higher photocatalytic performance versus NiCo 2 O 4 /g-C 3 N 4 . The recyclability and reusability of the nanocomposite were assessed and the Ni 1-x Mn x Co 2-y Fe y O 4 /g-C 3 N 4 showed promising stability. The Zea mays germination (%), root length (cm) and shoot length (cm) were compared, and the treated dye revealed significantly lower phytotoxicity versus the untreated dye solution. Results revealed that the Ni 1-x Mn x Co 2-y Fe y O 4 /g-C 3 N 4 composites have the potential for photocatalytic applications under solar light irradiation, which will make the process more economical versus other photocatalytic processes. • g-C₃N₄ and Ni₁₋ₓMnₓCo₂₋ᵧFeᵧO₄ composites was synthesized via co-precipitation and ultrasonication approach. • Solar-driven photocatalytic activity for crystal violet degradation was promising. • Treated dye phytotoxicity was reduced in Zea mays germination and growth. • Low recombination rates and bandgap tuning make photocatalysis cost-effective under visible light irradiation.