Green synthesis of rGO/Ag nanocomposite using extracts of Cinnamomum verum plant bark: Characterization and evaluation of its application for Methylene blue dye removal from aqueous solutions

We herein report the green synthesis of a reduced Graphene Oxide/Silver nanoparticle (rGO/AgNP) nanocomposite by simultaneously reduction of graphene oxide and silver ions using an aqueous extract of cinnamon (Cinnamomum verum) plant bark. Methylene blue dye removal capacity and efficiency of the nanocomposite was evaluated.  The synthesized nanocomposites were characterized by using UV‑DRS, SEM, P‑XRD, and FTIR spectroscopy. The XRD results showed the average particle sizes Ag NPs, rGO, and rGO/Ag NPs nanocomposite to 29.9 nm, 0.67 nm, and 13.35 nm respectively. The UV-DRS analysis result showed that rGO/Ag nanocomposite exhibited two absorbance peaks at 272 & 334 nm which corresponds to rGO and Ag NPs respectively. The FTIR spectral data revealed the functional groups characteristics of phytochemicals in the plant extract, rGO and rGO/AgNP nanocomposite. The surface morphology from SEM result obtained indicated that Ag NPs showed non-homogeneity and different shapes, rGO had thin flat layer sheet morphology whereas Ag NPs were deposited on rGO nanosheets in the form of clusters in the rGO/AgNP nanocomposite. The rGO/AgNP nanocomposite had highest methylene blue removal efficiency of 99.98% at optimum pH 2, adsorbent dose 80 mg, contact time 50 min and initial concentration of 10 mg/l. The Adsorption isotherms were well fitted to Langmuir isotherm for all synthesized adsorbents. The adsorption kinetics results were best fitted to the pseudo-second-order model. The green synthesized rGO/AgNP nanocomposite has the potential to be used as an adsorbent in wastewater treatment applications.