Nanotechnologies for Environmental Remediation by Giusy Lofrano Giovanni Libralato & Jeanette Brown

Author:Giusy Lofrano, Giovanni Libralato & Jeanette Brown
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

2.2.3 Graphene

Graphene is a two-dimensional NM and a single-atom layer of graphite that attracts the research interests because of its unique structure and exceptional properties. In particular, graphene-based materials offer a broad range of potentialities for wastewater decontamination and environmental remediation.

The graphene-based materials are deemed currently as “star materials” for the high-efficient removal of organic and inorganic pollutants from aqueous solution (Wang et al. 2013). In Table 1 the adsorption and the application in water treatment technologies of graphene-based materials for organic and inorganic contaminants removal are summarized.

Graphene-based composites have been applied to remove various organic contaminants, aromatic compounds (Li et al. 2012b; Kim et al. 2015; Wu et al. 2013a; Yang et al. 2015; Zhang et al. 2013), such as dyes (Li et al. 2011; Guo et al. 2016; Scalese et al. 2016), bisphenol A (Xu et al. 2012; Zhang et al. 2014), phenols (Li et al. 2012c, d) and antibiotics (Gao et al. 2012; Tang et al. 2013). Primary driving interactions are similar to those involved in CNTs surfaces, and as well different mechanisms may have simultaneous influences, such as electrostatic interactions, van der Waals type interactions, π-π bonds, anion-cation interaction and hydrogen bonds. According to the different adsorbates, different types of adsorption mechanisms will be predominant. For example, Ramesha et al. (2011) indicated that anionic and cationic dyes could be efficiently adsorbed by graphene and graphene oxide because of the high surface area and the negative surface charge. The interactions between the charged dyes and graphene are electrostatic, van der Waals type interactions or both depending on the system.

Three-dimensional (3D) graphene oxide sponge (GO sponge) has been shown to be excellent for contaminants removal. Also graphene/GO-composites improve the adsorptive performance of graphene by solving some limitations of this material in adsorption processes such as easy folding and aggregation. Therefore, a high number of applications have been developed. For example, methylene blue and methyl violet can be adsorbed on the GO sponge. This process involved in endothermic chemical adsorption through π-π bonds and anion–cation interactions with an activation energy of 50 and 71 kJ/mol (Liu et al. 2012a).

In another work, methylene blue was removed by adsorption (Liu et al. 2012b) using a composite of 3D graphene with Mg(OH)2 composite (Mg(OH)2–rGO), which presents high surface area and pore volume. In addition, this composite can be reused without almost no loss of adsorption after washing with ethanol. In a recent study, graphene oxide flakes functionalized with 3-amino-1-propanesulfonic acid (GOSULF) incorporated into an ionomer membrane as Nafion were proposed for water purification. The adsorption of and the posterior photo catalytic degradation on the GOSULF membrane (Nafion-GOSULF) of an anionic dye, methyl orange, were studied (Scalese et al. 2016). In another recent study, Wang et al., synthesized 3D flower-like TiO2 microsphere decorated graphene composite (FT/GN) based on the hydrothermal reduction of graphene oxide and formation of TiO2 microsphere in the presence of poly(vinyl pyrrolidine) (PVP). The TiO2 microsphere/graphene composite was used for removal of organic dye from water.

Good results have also been obtained for other organic pollutants such as antibiotics as tetracycline on GO.

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