Synthesis of M-rGO and M-rGO-sand coated reactive media for contaminant remediation

Nanomaterials have attracted much attention in recent decades for contaminant remediation purposes, due to their unique physical properties such as high surface area per unit volume, the ability to process functional groups on their surfaces to target specific pollutants, and the ability to adjust their characteristics such as size, morphology, porosity, and chemical composition according to the need. Among the nanomaterials, zero-valent iron, iron oxides, manganese oxides, activated carbon, carbon nanotubes and graphene have been most commonly used. Among these options, graphene attracts attention with its relatively large specific surface area, economic suitability and versatile structure that can be modified in various ways. It has the potential to be a good adsorbent in water treatment due to its two-dimensional layer structure, large surface area and pore volume, high mechanical stability, flexibility of surface chemistry and abundant production from natural resources. For efficient separation of the nanoadsorbent from the system, ease of operation and regeneration ability, magnetite (Fe3O4) reduced graphene oxide (M-rGO) can be used as an innovative reactive material for remediation of various contaminants from the subsurface. Although various protocols for producing magnetite reduced graphene oxide composite from graphite is available, uncertainties and/or differences were observed in the literature during the M-rGO material synthesis stage. In order to clarify these uncertainties, additional studies were carried out and some modifications were conducted. Under these modifications, different M-rGO samples were prepared, where surface characterization was compared with each other as well as with literature. This study focuses on the modifications conducted for the material synthesis of M-rGO for its optimum performance to be used as an adsorbent media for heavy metal removal.

In order for the nanocomposite M-rGO to be loaded into a porous environment such as a packed column to be used in larger-scaled implementations, it would need to be transferred to a larger size carrier which can provide a good support for the nanocomposite and also prevent M-rGO to separate from the medium during continuous flow experiments. For this purpose, available literature resources were compiled and a procedure is also proposed here for the coating of synthesized M-rGO onto sand particles. The chemical alteration of reactive M-rGO coated onto sand media is presented, showing the potential to be used for remediating contaminated groundwater.

Acknowledgement: This study is supported by TUBITAK (The Scientific and Technological Research Council of Turkey) 1001 Project with Grant Number 123Y025 and Research Fund of the Middle East Technical University, Research Universities Support Program (ADEP) with Grant Number ADEP-311-2022-11172.