Green synthesis of iron oxide nanoparticles using Momordica charantia: Kinetics of removal of heavy metal and microplastic pollutants

Abstract

Microplastics (MPs) and heavy metals (HMs) have been contributing widely to global environmental pollution. Green and eco-friendly synthesis of nanoparticles can be a cost-effective and sustainable approach to protect aquatic ecosystems and human well being. Plant extract based nanoparticles offer major benefits as they are safer, economic, easy to obtain and have good reduction and stabilization potential. Moreover, the active agents in plants are safer to handle than conventional chemicals and microbes. To aid to the mentioned objective, iron oxide nanoparticles (IONPs) were synthesized from the fruit extract of Momordica charantia by coprecipitation method. The characterization studies were carried out using Scanning electron microscopy (SEM), Ultraviolet- Visible spectroscopy (UV-Vis), FTIR (Fourier Transform Infrared Spectroscopy), and XRD (X Ray Diffraction). Spherical shaped, reddish brown nanoparticles with size ranging from 50–70 nm were fabricated. The potential and kinetics of IONPs for the removal of carcinogenic HMs such as Lead (Pb), Cadmium (Cd) and selected MP polymer Polyamide (PA) were further investigated. The Kinetics and isothermal models brought an insight into the removal rates of HMs and MP pollutants. While the polyamide removal was best explained by Pseudo-first order kinetics and Langmuir isotherm; pseudo second-order kinetics and Freundlich isotherm models could fit to the adsorption process between HMs (Pb, Cd) and IONPs. The synthesized IONPs could be used up to four cycles with maximum removal potential of 91.59, 92.52 and 89.43 percent for Pb, Cd and polyamide respectively in the first cycle. In order to check the safety of nanoparticles for environmental applications, phytoxicity studies were conducted. Seeds of Vigna radiata were used to study the toxic effects of each pollutant and the synthesized IONPs on the shoot and root growth. Thus, these preliminary findings of the current study indicate that IONPs synthesized using green pathway could contribute to removal of emerging contaminations from aqueous media, and offer potential approach for water purification, pending further mechanistic investigation.