A new BiOCl–ZnFe2O4/CNTs ternary composite for remarkable photocatalytic degradation studies of a herbicide and a diazo dye

Fabrication of binary or ternary nanocomposite of different semiconducting materials has received considerable attention for the development of an efficient, novel and realistic photocatalyst. Herein, we report the synthesis of BiOCl, spinel ZnFe2O4, BiOCl–ZnFe2O4 hybrid, and BiOCl–ZnFe2O4/CNTs ternary composite. Pure BiOCl and spinel ZnFe2O4 were synthesized by co-precipitation method while BiOCl–ZnFe2O4 hybrid and BiOCl–ZnFe2O4/CNTs ternary composite by an ultra-sonication approach. The prepared photocatalytic samples were scrutinized by X-ray diffraction (XRD) technique, Fourier transform infra-red (FTIR) spectroscopy, and UV–Visible (UV–Vis) spectroscopy. The calculated optical energy gaps of BiOCl and spinel ZnFe2O4 using Tauc equation were 3.21 eV and 2.19 eV respectively. The photocatalytic efficiency of all prepared photocatalysts was tested against a herbicide (Pendimethalin), and an anionic diazo dye (Congo red). The obtained results revealed that carbon nanotubes based ternary composite of BiOCl–ZnFe2O4 hybrid has high rate and percentage degradation for both pendimethalin and congo red among all synthesized materials. For pendimethalin removal, the value of rate constant of BiOCl–ZnFe2O4/CNTs is 0.01 min−1 and % degradation is 88.6 %. Moreover, BiOCl–ZnFe2O4/CNTs ternary composite exhibits 95.27 % degradation and rate constant of 0.02 min−1 for congo red dye. The higher photocatalytic removal activity of ternary composite (BiOCl–ZnFe2O4/CNTs) as compared to other fabricated photocatalysts is due to its high surface area, greater adsorption capability, high charge transfer rate and low e−/h+ pair recombination. Hence, BiOCl–ZnFe2O4/CNTs composite could be an efficient photocatalyst for the mineralization of various organic industrial effluents.