Rapid adsorption of methylene blue by synthesizing zinc oxide nanoparticles from Ocimum basilicum L. waste

Abstract In this study, zinc oxide nanoparticles (ZnONp) were synthesized from Ocimum basilicum L. ( Ob L-ZnONp) plant wastes by green synthesis method to remove methylene blue (MB) dye, which has toxic effects on the environment. In batch adsorption studies, the effects of pH (3–11), Ob L-ZnONp amount (0.0312–1.25 g/L), time (0–30 min), initial MB concentration (2–64 mg/L) and temperature (25–45 °C) were tested to determine the adsorption mechanism. The obtained results were tested with Pseudo first order (PFO), Pseudo second order (PSO), Elovich and Intraparticle diffusion kinetic models and evaluated in Freundlich, Langmuir, Temkin and Dubinin-Radushkevich isotherm models. Also 6 different error functions were used to interpret the results. Additionally, the morphological properties of the synthesized Ob L-ZnONp were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. In addition, desorption tests were also performed. According to the obtained results, the most suitable kinetic and isotherm models were determined as PSO (R 2 : 0.999) and Freundlich (0.991), respectively. In addition, while more than 90% removal efficiency was achieved in 4 min, the maximum adsorption amount was determined as 21.41 mgMB/g Ob L-ZnONp. This study determined that Np synthesized at low cost was quite effective in MB removal. Graphical abstract