Cotransport of Cu with Graphene Oxide in Saturated Porous Media with Varying Degrees of Geochemical Heterogeneity

Abstract

Graphene oxide (GO) is likely to encounter heavy metals due to its widespread use and inevitable release into the subsurface environment, where the ubiquitous presence of iron oxides (e.g., hematite) would affect their interaction and transport. The present study aimed to investigate the cotransport of GO (20 mg L−1) and copper (0.05 mM CuCl2) in the presence of varying degrees of geochemical heterogeneity represented by iron oxide-coated sand fractions (ω = 0‒0.45) in water-saturated columns under environmentally relevant physicochemical conditions (1 mM KCl at pH 5.0‒9.0). The Langmuir-fitted maximum adsorption capacity of Cu2+ by GO reached 137.6 mg g−1, and the presence of 0.05 mM Cu2+ decreased the colloidal stability and subsequent transport of GO in porous media. The iron oxide coating was found to significantly inhibit the transport of GO and Cu-loaded GO in sand-packed columns, which can be explained by the favorable deposition of the negatively charged GO onto patches of the positively charged iron oxide coatings at pH 5.0. Increasing the solution pH from 5.0 to 9.0 promoted the mobility of GO, with the exception of pH 7.5, in which the lowest breakthrough of GO was observed. This is possibly due to the fact that the surface charge of iron oxide approaches zero at pH 7.5, suggesting that new “favorable” sites are available for GO retention. This study deciphered the complicated interactions among engineered nanomaterials, heavy metals, and geochemical heterogeneity under environmentally relevant physicochemical conditions. Our results highlight the significant role of geochemical heterogeneity, such as iron oxide patches, in determining the fate and transport of GO and GO-heavy metal association in the subsurface environment.

Influence of Soil Colloids on Ni Adsorption and Transport in the Saturated Porous Media: Effects of pH, Ionic Strength, and Humic Acid

“…Moreover, as reported in the study, the colloids have the potential to promote the transport of heavy metals in soils and groundwater [19]. In recent years, the co-transport of colloids and contaminants has attracted widespread attention regarding environmental remediation due to its prevalence and efficient treatment in groundwater [20][21][22]. It was reported that colloids are well dispersed, which can provide highly potential adsorption material for heavy metal removal [23,24].…”

“…The effect of colloids on contaminant transport is dependent on hydrogeological conditions and physicochemical properties of the aquifers [27][28][29][30]. Both groundwater chemistry and site-specific conditions may promote or hinder the co-transport of heavy metals and natural colloids in the subsurface environment [20,28,29].…”

Transport of alumina nanoparticles in natural waters and water saturated porous media- an analysis of the effect of various environmental parameters

“…In the presence of HA, the BTCs demonstrate a delayed breakthrough of Al2O3NPs (Figure 6c). The NOM yields a negative surface charge and electrosteric stability to the Al2O3 NPs due to the binding of carboxylic (COOH) and phenolic functional groups (R-OH) to the surface of particle, which enhanced the Al2O3 transit along column (Davoudi et al 2014;He et al 2020;Rahman et al 2014). Also, the presence of HA increased the stability of the suspension and inhibits aggregation via improving electrostatic repulsion and steric hindrance as shown in the sedimentation experiments (Figure 6d).…”

Biosurfactant-mediated mobility of graphene oxide nanoparticles in saturated porous media

“…1,2 The rapid increase in the use of this carbon-based nanomaterial will inevitably lead to the release of GO into environmental systems (e.g., soil, surface water, and aquifers). 1,3,4 Recent studies have conrmed that harmful effects on natural ecosystems and living organisms have occurred aer exposure to GO. [5][6][7][8] Understanding the transport, deposition, and fate of GO colloidal particles in subsurface formations is of great importance for numerous applications, regulatory approaches, and environmental concerns.…”