Design and Optimization of Polyindole-Integrated Bimetallic Composites (PLN/CuO-NiO and PLN/Mn-Cu) for Efficient Photocatalytic Degradation of Imidacloprid under Sunlight Irradiation

Abstract

The present study demonstrated the fabrication of novel polyindole (PLN) based-bimetallic nanocomposites (PLN/Mn-Cu and PLN/CuO-NiO) via coprecipitation, hydrothermal, and in-situ polymerization methods, for the photodegradation of imidacloprid (IMI) pesticide. Fourier transform infrared spectroscopy showed that PLN were successfully loaded onto the bimetallic nanocomposites' surface. X-ray diffraction analysis revealed that PLN/Mn–Cu exhibited a cubic phase with a crystallite size of 75 nm, while PLN/CuO–NiO retained cubic CuO and monoclinic NiO phases with a size of 54 nm. Scanning electron microscopy analysis showed that PLN/CuO–NiO featured spherical but irregular structures, while PLN/Mn–Cu exhibited a granular and uneven surface morphology. UV–visible analysis showed band gaps of 2.15 eV (PLN/Mn–Cu) and 2.13 eV (PLN/CuO–NiO), with strong absorption between 250–350 nm, confirming their visible-light photocatalytic potential. Photocatalytic activity of PLN/Mn–Cu and PLN/CuO–NiO composites exhibited a 91 and 98 % degradation efficiency of IMI pesticide under optimum conditions of pH = 10 and 4, catalyst dose = 5 mg/L, irradiation time = 120 min and 60 min, and pesticide dose = 2 and 6 mg/L, respectively. The kinetic study showed that the Behnajady-Modirshala-Ghanbery model fitted best to the experimental data. The study on reusability showed that catalysts can be used in five consecutive cycles. The work also demonstrates a sustainable and promising route for designing PLN-functionalized bimetallic nanocomposites for environmental remediation applications.