Thiourea-Modified Graphene Oxide for Enhanced Heavy Metal Removal from Aqueous Solutions
Both lead (Pb²⁺) and hexavalent chromium (Cr(VI)) are highly toxic pollutants which need to have strategies for their removal. In this work, graphene oxide (GO) and thiourea-functionalized graphene oxide (TU-GO) were prepared and characterized by means of scanning electron microscopy (SEM), FTIR, Raman, UV-Vis, and BET analyses. Compared to GO, TU-GO showed higher surface area and enriched N/S functional groups. For adsorption experiments, an equilibrium was rapidly reached for Pb²⁺ and was slower for Cr(VI) uptake. Isotherm analysis revealed Pb²⁺ adsorption was Langmuir type monolayer, while Cr(VI) adsorption was better described by the Freundlich model. Kinetic results confirmed the pseudo-first order model was best and TU-GO reached higher rates. From thermodynamic parameters, adsorption was spontaneous, endothermic, and favored by increased entropy. As a whole, TU-GO outperformed other adsorbents, proving that it can effectively be used to remove heavy metals from water.