Enhanced Hg(II) removal using thiourea-functionalized graphene oxide: Lab to pilot scale evaluation

Abstract

Here, a thiourea-formaldehyde functionalized graphene oxide (G3DTF) is shown to effectively remove mercury (Hg) from various water sources, including ultrapure, bottled, and seawater. Over 99 % of the Hg in each water source is removed with only 10 mg/L of G3DTF resulting in a residual Hg concentration < 1 μg L−1. This concentration falls within the permissible limits established by the European drinking water guidelines. Notably, the presence of chlorocomplexes in seawater does not reduce the sorption efficiency of G3DTF. The sorption process across all water matrices can be accurately described by pseudo-second-order kinetics, with an R2 > 0.99 suggesting chemical interactions between Hg ions and G3DTF functional groups. The equilibrium isotherms demonstrate a remarkably high maximum adsorption capacity (qm) of 1039 mg g−1, exceeding the values reported in literature for the sorption of Hg on carbon-based materials. Remarkably, G3DTF retains its performance in the presence of other metal ions such as Cu, Cd, and Pb. Incorporating G3DTF into commercially activated carbon (AC) at a concentration as low as 2 wt % significantly enhances the efficiency of Hg(II) removal in fixed bed adsorption. The breakthrough curve exhibits enhanced absorption, attaining a 99.7 % removal of Hg(II) within a span of 2 h, surpassing the efficiency of AC. This relevant result represents a substantial advancement towards the adoption of graphene-based nanocomposites as effective commercial remediation materials.