Highly efficient surface sequestration of Pb2+ and Cr3+ from water using a Mn3O4 anchored reduced graphene oxide: Selective removal of Pb2+ from real water

Abstract

Owing to the ubiquitous existence of detrimental heavy metals in the environment, simple adsorption-oriented approaches are becoming increasingly appealing for the effective removal of Pb2+ and Cr3+ from water bodies. These techniques use nanocomposites (NC) of reduced graphene oxide (rGO) and Mn3O4 (rGO-Mn3O4), they employ a hydrothermal technique featuring NaBH4 and NaOH solutions. Here, spectroscopic and microscopic instrumental techniques were used to evaluate the morphological and physicochemical characteristics of prepared reduced graphene oxide manganese oxide (rGO-Mn3O4), revealing that it possessed a well-defined porous structure with a specific surface area of 126 m2 g−1. The prepared rGO-Mn3O4 had significant adsorption efficiencies for Pb2+ and Cr3+, achieving maximum sequestration capacities of 130.28 and 138.51 mg g−1 for Pb2+ and Cr3+, respectively, according to the Langmuir model. These adsorption capacities are comparable to or greater than those of previously reported graphene-based materials. The Langmuir isotherm and pseudo-second-order models adequately represented the experimental results. Thermodynamic analysis revealed that adsorption occurred through spontaneous endothermic reactions. Recycling studies showed that the developed r-GO-Mn3O4 had excellent recyclability, with <70% removal at the 5th cycle; its feasibility was evaluated using industrial wastewater, suggesting that Pb2+ was selectively removed from Pb2+ and Cr3+ contaminated water. The instrumental analysis and surface phenomena studies presented here revealed that the adsorptive removal processes of both heavy metals involved π electron donor-acceptor interactions, ion exchange, and electrostatic interactions, along with surface complexation. Overall, the developed rGO-Mn3O4 has the potential to be a high-value adsorbent for removing heavy metals.