Evaluation of Imidacloprid adsorption on a new activated carbon based nanocomposite consisting of magnetite and copper oxide nanoparticles: Adsorption modelling, optimisation, and characterisation

Standard purification systems have mainly demonstrated the inefficient removal of neonicotinoid insecticides with high persistence in the environment. In the present work, a new magnetic adsorbent composed of Fe3O4 and CuO nanoparticles impregnated with activated carbon (AC) has been used to remove imidacloprid (IMCP) as the most common neonicotinoid insecticide from the water solutions. Various techniques such as Fourier Transform infrared spectroscopy, x-ray diffraction, field emission scanning electron microscopy, energy-dispersive x-ray diffraction, and vibrating sample magnetometer were employed to characterise the fabricated composite. The main affecting parameters, including adsorbent amount, solution pH, agitating time, initial pesticide concentration, and temperature, were examined to obtain the optimised conditions. According to the obtained results from kinetic and isotherm modelling, the adsorption mechanism of IMCP on Fe3O4/CuO@AC nanocomposite (NC) is a combination of chemisorption and physisorption phenomena. The presence of heterogeneous sites for IMCP adsorption was shown by fitting the experimental data to the Freundlich isotherm model. In addition, the adsorption process was well consistent with the pseudo-second-order kinetic model, which indicates that chemisorption is the determining step in the adsorption process. Thermodynamic data showed the exothermic and spontaneous nature of the adsorption process. Under optimal conditions (initial concentration of pesticide 10 mg L−1, pH = 7, and contact time of 10 min), 99.6% of IMCP was effectively removed, indicating the excellent ability of the adsorbent to adsorb this insecticide from aqueous solutions.