Surfactants for dispersion of carbon nanotubes applied in soil stabilization

Abstract

a b s t r a c tThe discovery of the unique properties of carbon nanotubes (CNT) did grow interest to its application in nanocomposites, for a wide variety of purposes. However, the greatest challenge for its application is associated with the natural tendency to aggregate, resulting in the loss of its beneficial properties. To overcome this problem it is common the use of surfactants and/or ultrasonic energy to promote their dispersion in suspension. This work is focused on the influence of surfactants' properties on the dispersion of carbon nanotubes and on the influence of the quality of the dispersions on the mechanical properties of stabilized soil. Two surfactants (Glycerox and Amber 4001 differing in molecular weight and charge) were fully characterized, followed by the study of which surfactant concentrations were more efficient on the dispersion of the CNTs. The characterization methods were based on light scattering techniques: Dynamic Light Scattering (DLS) for the hydrodynamic diameter and Static Light Scattering (SLS) for the molecular weight. Suspensions of CNTs were prepared in solutions of the aforementioned surfactants, with different concentrations, and further dispersion was promoted using ultra-sounds (20 kHz during 5 min). The dispersions of CNTs in these two surfactants were then fully characterized using again DLS. Finally, the dispersions of carbon nanotubes were added to the main agent responsible for soil stabilization, the binder (Portland cement type I 42.5R), and the mechanical behavior of the new composite material was studied by unconfined compression strength (UCS) tests. The results of the UCS tests led to conclude that the introduction of CNTs in the binder can have huge impact on the mechanical properties of the stabilized soil. Furthermore, the quality of the dispersion of CNTs has got a very high impact on the performance achieved. It was verified an improvement up to 77% on the compressive strength of the material and 155% on Young's modulus, referred to the reference test where no carbon nanotubes nor surfactant were added, fundamentally dependent on surfactant type and concentration used.

Improvement of Marine Clay Soil Using Lime and Alkaline Activation Stabilized with Inclusion of Treated Coir Fibre

“…A good dispersion of the admixture particles will lead to better filling of the pores between soil particles with the inclusion of fibre in making a soil matrix more stiff. The statement was the same trend with [48][49][50] in which the usage of cement is a good dispersion as it will lead to a better filling of spaces between the soil particles making the solid matrix more resistant. Other than that, as commonly known, lime and fly ash can disperse the admixture particles that improve soil strength.…”

Heavy Metals Removal from Aqueous Solutions by Multiwall Carbon Nanotubes: Effect of MWCNTs Dispersion

“…Pb (II) is a cation with an electronegativity around 2.33 on the Pauling scale [ 47 ], which means that it has more tendency to be removed than the other metals. Regarding electronegativity, Pb (II) is followed by Cu (II), Ni (II) and Zn (II), with values of electronegativity of 1.91, 1.90 and 1.65, respectively [ 45 ]. The difference in removal of Ni (II) and Cu (II), with similar electronegativity, may be attributed to the higher atomic radius of Ni (II) (149 pm for Ni (II) and 128 pm for Cu (II)), [ 45 ].…”

“…They are composed of 90% ( w / w ) of pure carbon and 10% ( w / w ) of metallic oxides. Further tests completed the characterization of the MWCNTs supplying information about density (1.7 g/cm 3 ) and zeta potential at neutral pH (−25.2 mV) [ 44 , 45 ].…”

Comparison of Nanomaterials with Other Unconventional Materials Used as Additives for Soil Improvement in the Context of Sustainable Development: A Review

“…The shear strength of cement-reinforced soil in UCS test increases with the CNTs content when suitable dispersant is added. However, more CNTs would hinder the potential bond between cement and soil particles, and thus excessive CNTs will decrease stiffness and the strain at failure, which can induce a ductile behavior in the sample [ 38 ]. On the other hand, CNTs can not only play an important role in improving mechanical properties for a soil sample, but also can be used to absorb some organic material (polyaromatic hydrocarbons etc.)…”