DENDRIMER AND ACID FUNCTIONALIZED MAGNETIC GRAPHENE OXIDE FOR LEAD (Pb) REMOVAL FROM AQUEOUS SOLUTION

Abstract

Synthesis and optimization of nano sorbents for lead (Pb) removal from water is challenging. In this study, graphene oxide (GO) was decorated with magnetic nanoparticles (MNPs) in various weight ratios (20%­70%). Polyamidoamine dendrimers were anchored on the GO­MNP composites to passivate MNP surface and generate amine­terminal groups on GO, which were functionalized with four different organic acids to construct cage­like structures for Pb removal from contaminated water. The composites were characterized using transmission electron microscope, scanning electron microscope, energy dispersive spectroscopy, X­ray diffraction, Raman spectroscopy, Fourier transform infrared, thermogravimetric, and zeta potential analysis. The Pb removal increased significantly with GO weight percentage up to 40% resulting in 51% Pb removal in 24 h. The organic acid functionalization improved the Pb removal by adsorption through electrostatic attraction, hydrogen bonding, and π­ π interactions. Pb removal efficiency of citric acid (CA), gallic acid (GA), succinic acid (SA), and vanillic acid (VA) functionalized GO­MNP was 94%, 71%, 88%, and 66%, respectively. The highest removal efficiency of GO­MNP­CA was attributed to the linear structure of CA and the number of adsorptive sites per molecule. The monolayer adsorption hypothesis has been bolstered by the Langmuir model’s superior fit to the Pb adsorption over the Freundlich model. GMNP­CA attained 23.5 mg/g adsorption capacity at an equilibrium adsorption time of 150 min with 100 mg/L dosage of adsorbent that possesses the ability due to the presence of tricarboxylic groups. GMNP­CA maintained 90% Pb adsorption in the tenth cycle of the reusability experiment which suggested to be best for practical application.