Fabrication of thymine immobilized magnetic graphene oxide for the efficient removal of mercury and melamine

Abstract

The presence of harmful inorganic pollutant mercury (Hg2+) and organic contaminant melamine in wastewater causes serious environmental and health problems. Various methods or techniques have been applied for the removal of melamine and mercury from wastewater. Among those methods, the adsorption method has received much attention due to its high efficiency, simplicity and economic validity. In this study, we exploited the strong selective interaction of mercury and melamine with thymine to develop a composite material for the adsorption of these contaminants. Specifically, magnetic graphene oxide was modified by a thymine derivative, 1-trimethoxysilyleundecyle-thymine (1-TMSU-T), to introduce higher Hg (II) and melamine adsorption capacity. The fabrication of thymine-modified magnetic graphene oxide was carried out in two procedures for comparison. In the first procedure, magnetic nanoparticles (Fe3O4) were initially coated with thymine and then hydrothermally treated with GO before another thymine modification (hereafter denoted as MTGOT). In another procedure, magnetic graphene oxide (MGO) was directly treated with (1-TMSU-T) in one step to introduce the thymine molecules on the surface (hereafter denoted as MGOT). The fabricated nanomaterials were characterized employing FTIR, XPS, FESEM, EDX and magnetization. The magnetization (magnetization vs magnetic field) hysteresis of the nanomaterials confirmed the magnetic nature of the synthesized materials. Remarkably, these materials exhibit excellent melamine removal performance and high Hg2+ adsorption capacities which reveled in different adsorption tests of melamine and Hg2+. MTGOT and MGOT had a Hg2+ adsorption capacity of 16.1 mg g–1 and 12.4 mg g–1, respectively. It was found that MTGOT and MGOT could remove 94.5% and 77.4%, respectively, of a 20 mL 50 ppm solution.