Synthesis and characterization of silver nanoparticles and nanocomposites using Echinochloa pyramidalis (Antelope grass) plant parts and the application of the nanocomposite for the removal of PAHs from bitumen seepage water

Abstract

Aqueous extracts of the leaf, stem and root of Echinochloa pyramidalis have been used as a reducing agent to synthesise silver nanoparticles. The synthesized nanoparticles were characterized by UV, FTIR, SEM, TEM and XRD. The nanoparticles showed absorption spectra in the visible region and particle sizes of 14, 2.70 and 4.9 nm for the leaf, stem and root-based nanoparticles while the respective crystalline sizes were 15.3, 12.6 and 10.3 nm respectively. The FTIR spectra of the nanoparticles indicated evidence of changes in the functional groups that indicated an interaction between the nanoparticles and the phytochemicals in the respective plant parts. Micrographs obtained from scanning electron microscope (SEM) reveal some protruding internal structures. The synthesized nanoparticles were also used as precursors to synthesize nanocomposites by combining them with the leaf, stem and root of the Echinochloa pyramidalis of the plant. The nanoparticles and the corresponding nanocomposites showed pore sizes that define mesoporous dimension, functional groups that were comparable to those in the parent nanoparticles, and modified surface morphology. However, BET surface area to volume ratios were relatively higher for the composites than the nanoparticles while the reverse trend was observed for pore diameter and pore volume. The composites were found to be excellent adsorbents for the removal of some PAHs from bitumen seepage water and recorded an average minimum removal efficiency of 90% and a maximum of almost 100%.