One-step green synthesis of Nerium oleander-capped Fe/Cu bimetallic nanoparticles for high-efficiency adsorption of methylene blue

Abstract

The perpetual release of organic industrial pollutants into the environment increases the aquatic and human health risks. Adsorption technology is an easy and highly effective way for the decontamination of polluted water. In this investigation, Fe/Cu bimetallic NPs are prepared by a green method from the extract of the Nerium oleander plant leaf as a stabilizing and reducing agent. The produced bimetallic NPs are examined for their structural features and performance. The characterization results showed that the stabilized hybrid material is quite stable and predominantly amorphous with a mesoporous structure. The surface area, averaged pore diameter, and the pore volume of Fe/Cu bimetallic NPs are found to be 26.07 m²/g, 14.38 nm, and 0.0937 cm³/g, respectively. The dye is selected as the simulated contaminant to assess the adsorbent's efficacy in the organic’s removal from wastewater. The adsorbent effectively adsorbed 94.2% of the contaminant with a high adsorption capacity of 156.40 mg/g at a primary concentration of methylene blue = 20 mg/L; dose = 0.02 g; solution pH = 10; temperature = 25 °C; mixing time = 130 min. The adsorption process of methylene blue by Fe/Cu bimetallic NPs followed the pseudo-second-order adsorption kinetics and the Freundlich adsorption isotherm. Studying the thermodynamics resulted in negative Gibbs free energy, negative enthalpy, and negative entropy, which means that the adsorption is exothermic, spontaneous, and more ordered.