Hydrothermal Synthesis of Fluorescent Schiff Base Functionalized Carbon Dot Composite for The Removal of Cd(II) Ions from Aqueous Solution: Optical, Equilibrium and Kinetic Studies

Abstract

The search for nanoparticle metal chelator biomarker has been on the rise in recent years. In thisstudy, bis(salicylidene)ethylenediamine (SALEN) functionalized carbon dot derived from waste banana peelswas synthesized using facile hydrothermal technique and the optical biomarker and adsorption properties of thehighly fluorescent red nanomaterial was studied. The carbon dot and its functionalized counterpart werecharacterized using FTIR, SEM/EDX, and UV-Visible spectrophotometry. Evaluation of the optical properties ofthe yellowish brown carbon dot and reddish highly luminescent functionalized carbon dot indicated band gapenergy values of 1.85 and 2.04 eV, respectively. Extraneous variables such as effect of initial metal ionconcentration, pH, and contact time were studied in the batch extraction process for the sorption of Cd(II) ionsfrom aqueous solution. The sorption of Cd(II) ion was observed to be highest at pH 5 with 99.3 % removalefficiency. The adsorption isotherm and kinetic models indicated interplay of physisorption and chemisorptionprocesses. The mechanism for the chelation of Cd(II) ions onto the surface of the functionalized carbon dot wasmainly governed by inner sphere chelation and ion exchange. Reusability of the material was evaluated usingadsorption-desorption experiments. Results of the study indicated the potential of the functionalized carbon dotas (i) semiconductor materials with strong photoluminescence at the visible region which could be used asenvironmental biomarker and as sensor, and (ii) effective, efficient and low cost adsorbent for remediatingCd(II) ions contaminated environment.