Environmental Remediation Applications of Carbon Nanotubes and Graphene Oxide: Adsorption and Catalysis

Abstract

Environmental issues such as the wastewater have influenced each aspect of our lives. Coupling the existing remediation solutions with exploring new functional carbon nanomaterials (e.g., carbon nanotubes, graphene oxide, graphene) by various perspectives shall open up a new venue to understand the environmental issues, phenomenon and find out the ways to get along with the nature. This review makes an attempt to provide an overview of potential environmental remediation solutions to the diverse challenges happening by using low-dimensional carbon nanomaterials and their composites as adsorbents, catalysts or catalysts support towards for the social sustainability.

Keywords: adsorption; carbon nanomaterials; carbon nanotubes; catalysis; environmental remediation; graphene; graphene oxide.

Figure 1

The general trend for the changes of CNT adsorption properties after different treatments. Reprinted with permission from [23]. Copyright (2008) American Chemical Society.

Figure 2

Schematic representation of the advantageous performances of the caged MWCNTs on dye adsorption. Reprinted with permission from [25]. Copyright (2008) American Chemical Society.

Figure 3

(A) Prussian blue was sealed into the cavities of the diatomite (upper, lower resolution). The diatomite surfaces were coated with highly dispersed multi-walled CNTs (upper, high resolution). The CNTs formed a continuous, interconnected network that prevented the diffusion of Prussian blue particles. (B) Representative SEM images of the quaternary (polyurethane polymer, CNTs, diatomite, and Prussian blue, PUP/CNT/DM/PB), spongiform, Prussian blue based adsorbent. Reproduced with permission from [57]. Copyright Elsevier, 2012.

Figure 4

(a) Schematic illustration of biomimetic N-doped CNT (NCNT)/TiO₂ core/shell nanowire fabrication. Red, blue, and yellow colors indicate TiO₂ precursor, pyridinic N (NP), and quaternary N (NQ), respectively. N-doping sites act as nucleation sites. (b) ADF-STEM image of NCNT. EELS mapping shows (c) C and (d) N elements along NCNT. (e) TEM and (f) SEM images of NCNT/TiO₂ core/shell nanowires. The inset shows the lattice distance of the anatase phase. (g) NCNT/TiO₂ core/shell (top) and bare NCNT (bottom) heteronanowires. Reprinted with permission from [78]. Copyright (2012) American Chemical Society.

Figure 5

Schematic showing the preparation process of the SWCNT/TiO₂ nanocomposite film and for separation of an oil-in-water emulsion. Reprinted with permission from [75]. Copyright (2014) American Chemical Society.

Figure 6

Hydroxyl multi-walled carbon nanotube-modified nanocrystalline PbO₂ anode for removal of pyridine from wastewater. Reproduced with permission from [80]. Copyright Elsevier, 2017.

Figure 7

Mechanism of peroxymonosulfate (PMS) activation on N-Doped CNTs. Reprinted with permission from [83]. Copyright (2015) American Chemical Society.

Figure 8

(A) The schematic diagram of conventional one–step adsorption; (B) Enhanced two-step adsorption: simultaneously generate new sites from inactive structures for enhanced capacity.

Figure 9

(A) Time-dependent adsorption of dye acridine orange by GO, in-situ reduced GO(SRGO), three-hour-long pre-reduced GO (LRGO) versus the blank group, AO ~100 mg/L, 50 mL; (B) Adsorption isotherms fitted by the Langmuir model: the reciprocal of equilibrium concentration versus that of equilibrium capacity. Adapted with permission from [99]. Copyright Elsevier, 2012.

Figure 10

(A) Ca²⁺ cross-linked GO-alginate composite beads(SA-GO-N); (B) Acid-gelled GO-alginate composite beads (SA-GO-M);(C) a SEM image of freezing-dry bead SA-GO-N; (D) a SEM image of the bead SA-GO-M; (E) naked-eye comparison of color changes upon dye-adsorbing beads (SA-GO-M and SA-GO-N) were immersed in the CaCl₂ ~0.5 mol/L solution and deionized water. Adapted with permission from [119]. Copyright Elsevier, 2014.

Figure 11

Schematic explanation for morphology evolution of the representative Ag@AgCl@Graphene nanocomposites (A). SEM images of the as-prepared cubic Ag@AgCl and quasi-cubic Ag@AgBr nanoparticles encapsulated by gauze-like graphene sheets in Ag@AgCl@Graphene (B, upper) and Ag@AgBr@Graphene (B, lower), respectively. Photocatalytic performance of the thus-prepared Ag@AgX@Graphene plasmonic photocatalysts for the degradation of the AO pollutant under sunlight irradiation (C). Reproduced with permission from [130]. Copyright Royal Society of Chemistry, 2013.