An insight into Cu/Gd co-doping and MWCNTs modification on SrFe12O19 for effective removal of industrial effluents

Abstract

Estimation of Urbach energy profiles and tailoring the structural and optical properties of semiconducting materials as photocatalysts can be helpful for the effective treatment of wastewater. In this aspect, pure SrFe₁₂O₁₉ and Cu/Gd@SrFe₁₂O₁₉ were synthesized via co-precipitation route, and carbon nanotubes (CNTs)-based composite of Cu/Gd@SrFe₁₂O₁₉ was synthesized by an ultra-sonication method. The structural analysis of all prepared samples showed a considerable decrease in crystallite size (13.8 nm) for Cu/Gd@SrFe₁₂O₁₉/CNTs nanocomposite as compared to pure SrFe₁₂O₁₉ (20 nm). The bandgap energy of Cu/Gd@SrFe₁₂O₁₉ was decreased to 2.43 eV as compared to SrFe₁₂O₁₉ (2.64 eV), and Urbach energy of Cu/Gd@SrFe₁₂O₁₉/CNTs composite was increased to 1.85 eV as compared to SrFe₁₂O₁₉ (1.56 eV) and Cu/Gd@SrFe₁₂O₁₉ (1.63 eV). Moreover, the results obtained from photoluminescence (PL) spectroscopy revealed that the CNTs-based photocatalyst exhibited less electron/hole pair recombination rate as compared to its other counter parts that was further confirmed by its improved photocatalytic efficiency. The photocatalytic activity of SrFe₁₂O₁₉, Cu/Gd@SrFe₁₂O₁₉, and Cu/Gd@SrFe₁₂O₁₉/CNTs composite was determined against bromocresol blue (BCB) and methyl orange (MO) under solar light irradiation of about 60 min. The as fabricated SrFe₁₂O₁₉, Cu/Gd@SrFe₁₂O₁₉, and Cu/Gd@SrFe₁₂O₁₉/CNTs showed about 68%, 79%, and 87.6% degradation of BCB, respectively. In addition, about 65%, 79%, and 92% degradation of MO was observed by SrFe₁₂O₁₉, Cu/Gd@SrFe₁₂O₁₉, and Cu/Gd@SrFe₁₂O₁₉/CNTs, respectively. The estimated results deduce that the outstanding photocatalytic activity of a novel nanocomposite (Cu/Gd@SrFe₁₂O₁₉/CNTs) for both BCB and MO is accredited to the combined effect of narrow bandgap of co-doped SrFe₁₂O₁₉ and high specific surface area, small crystallite size, and high charge separation ability of MWCNTs. Hence, Cu/Gd@SrFe₁₂O₁₉/CNTs composite could be an efficient photocatalyst for the degradation of various harmful pollutants.

Graphical Abstract