Graphene based metal oxide nanocompocites for heavy metals remediation in water

1. GRAPHENE-BASED METAL
OXIDE NANOCOMPOCITES
FOR HEAVY METALS
REMEDIATION IN WATER
CHE 690 SEMINAR
By
Sifiso Shongwe
Supervisor: Dr Kibechu

2. Content
1. Graphene and graphene oxides
2. Metal Oxide Nanocomposites
3. Synthesis of graphene and graphene oxides
4. Synthesis of Graphene-based Metal Oxide Nanocomposites
5. Characterisation
6. Application
7. Limitations
8. Conclusion

3. Graphene
 Graphene can be described as a one-
atom thick layer of graphite.
 It is the basic structural element of
other allotropes, including graphite,
charcoal, carbon nanotubes and
fullerenes.
 Graphene is the strongest, thinnest
material known to exist.
Graphene is an atomic-scale
honeycomb lattice made of
carbon atoms.

5. History of Graphene
 Two years later, in 2004 professor Geim and former
student Novoselov at University of Manchester extracted
single-atom-thick crystallites from bulk graphite
 Geim and Novoselov received several awards for their
pioneering research on graphene, notably the 2010 Nobel
Prize in Physics
2010 Nobel Prize
winners

6. Structure of Graphene
 Graphene is a 2-dimensional network of carbon atoms.
 These carbon atoms are bound within the plane by strong
bonds into a honeycomb array comprised of six-membered
rings.
 By stacking of these layers on top of each other, the well
known 3-dimensional graphite crystal is formed.
 It is a basic building block for graphitic materials of all
other dimensionalities.
 It can be wrapped up into 0D fullerenes, rolled into 1D
nanotubes or stacked into 3D graphite.
 Thus, graphene is nothing else than a single graphite
layer.

8. Properties of Graphene
 High surface area
 Conducts electricity
 Mechanical flexibility
 Stronger than diamond and 300 times stronger than steel

9.  Graphene has attracted the attention of the scientific
community for its fascinating physical and chemical
properties.
 To date, great efforts have been made to combine a varieties
of nanomaterials with graphene and explore their application
in water purification.
 In recent years, graphene-based iron oxide (Fe3O4)
nanocomposites have attracted much interest and have been
used as adsorbents for the removal of heavy metals and
other organic contaminants from the environment due to
their magnetic properties and high surface to volume ratio.

10. 2.1 Synthesis of Graphene
Two basic technique used are :
1. Mechanical exfoliation (ME)
2. Chemical vapour deposition (CVD)
ME with adhesive tape
CVD on copper surface
heat

12. Synthesis of graphene oxide by
Hammer’s method

13. Synthesis of Metal oxide Nanoparticles
Sol-gel Method

14. Synthesis of MnO2 (Np)

15. Synthesis of Graphene-based Metal
Oxide Nanocomposites
Suspend
RGO in
water
Mix with
KMnO4
powder
Microwave
for 5
minutes
e.g. G-MnO2 synthesis
Microwave assisted method

16. Characterization
Morphology and size
1. Scanning electron microscopy (SEM)
2. Transmission electron microscopy (TEM)
Purity and size
1. X-ray diffraction (XRD)
Layers of graphene and graphene oxide
1. Raman spectroscopy
Functional groups of the functionalize NPs
1. Fourier-transform infrared spectroscopy(FT-IR)
Raman

17. The Use of Graphene-Based Metal Oxides
Nanocomposites for Heavy Metal Removal in
Water
The first use of graphene as a heavy metal remediation
adsorbent was conducted by Chandra et al. who showed that
arsenic could be removed easily from contaminated water. In
their study a water dispersible graphene magnetite G-Fe3O4
composite was synthesized by the simultaneous reduction of
graphene, FeCl2 and FeCl3. The composite showed the formation
of 10 nm magnetite nanoparticles on the reduced graphene oxide
(rGO) sheets. The composite material showed a high binding
capacity for As(III) and As(V) resulting in the removal of 99.9%
arsenic in water. Due to the intrinsic nature of this material it
can be easily magnetically separated from purified water.

18.  Zhang et al. have shown that 95% arsenate removal over the pH 4 -7
range can be achieved using a cross-linked ferric hydroxide-GO
composite. The cross linkage between the graphene sheets was obtained
by the oxidation of ferrous sulphate using hydrogen peroxide.
 Zhu et al. have also developed graphene decorated with Fe-Fe2O3
nanoparticles which show efficient adsorption capacity for As(III) in
polluted water. This method uses Fe2O3 which increases the total
adsorption sites, while the Fe core makes the material separable by
using a strong magnetic field.
 Kemp and co-workers expanded further on this work, by showing that
the introduction of MnO2 nanoparticles into a Fe3O4-rGO material
increases the pH range of effective As(III) and As(V) adsorption.

19. Limitations
 Engineering applications demand massive production of high-
quality graphene with controllable layers, sizes, compositions
by a rapid, economic, and energy efficient process.
 The properties and functions of the composites depend
strongly on their microstructures. Therefore, a more careful
design of the composites is required to obtain higher quality,
more uniform morphology on the nanoscale and better
adsorption properties.
 The mechanism of adsorption enhancement by graphene-
metal oxide composites are relatively uncertain.

20. Conclusion
 Graphene has attracted much attention because of its unique
properties and potential applications.
 It is synthesized and modified through various methods. When
graphene is functionalized with nanocomposites such as
metal oxides nanoparticles it increases its absorption
capacity for heavy metals in water.
 low cost a efficient method for heavy metal remediation in
water.

21. References
 Burakov, A. E. et al., 2018. Adsorption of heavy metals on
conventional and nanostructured materials for water treatment
purposes: a review. Ecotoxicology and Environmental Safety 148, pp.
702-712.
 Chandra , V. et al., 2010. Water-dispersible magnetite-reduced
graphene oxide composites for arsenic removal. ACS Nano, 4(7), pp.
3979-3986.
 Gottipati, R. & Susmita, M., 2012. Application of response surface
methodology for optimization of Cr(III) and Cr(VI) adsorption on
commercial activated carbons. Research Journal of Chemical
Sciences, pp. 40-48.
 Kemp, C. k., Seema, H., Saleh, M. & Chandra, V., 2013. Environmental
applications using graphene composites: Water remediation and gas
adsorption. Nanoscale, 5(8), p. 3149

22. THANK YOU