Impact of surfactant and clay platelets on electrokinetic potential and size distribution in carbon nanotubes aqueous suspensions

Manilo, Maryna; Bohács, Katalin; Lebovka, Nikolaï; Bárány, Sándor

doi:10.1016/j.colsurfa.2018.02.030

Cited by 12 publications

(10 citation statements)

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“…2 presents examples of ζ-potential and PDA aggregation ratio, R PDA , versus concentration of CTAB, C s , in aqueous suspension of MWCNTs (C n = 0.003 % wt.) [29,30]. A change in the ζ-potential from negative to positive values with increasing the CTAB concentration, C s , was observed.…”

Section: Regulation Of Colloidal Stabilitymentioning

confidence: 89%

“…Cationic surfactant CTAB was widely used for stabilization of carbon nanotubes in aqueous suspensions [26][27][28][29][30]. The CTAB molecule has length of 2.33 nm, and its critical micelle concentration (CMC) in water is ≈ 1 mM (0.0364 % wt).…”

Section: Regulation Of Colloidal Stabilitymentioning

confidence: 99%

“…Isotherm of adsorption of CTAB on the MWCNT surface and behavior of ζ-potential in the presence of CTAB were investigated in a number of works [27][28][29][30]. The aggregation stability was quantified using photometric dispersion analyzer (PDA) in a flow system by the PDA aggregation ratio R PDA [31].…”

Section: Regulation Of Colloidal Stabilitymentioning

confidence: 99%

“…The dispersibility of carbon nanotubes in the presence of CTAB and aggregation stability of MWCNTs were studied in different works [26,29,30,32]. The optimum concentration of CTAB to achieve homogeneous dispersibility of carbon nanotubes in aqueous suspensions was identified to be near the CMC [26,32].…”

Section: Regulation Of Colloidal Stabilitymentioning

confidence: 99%

“…The optimum concentration of CTAB to achieve homogeneous dispersibility of carbon nanotubes in aqueous suspensions was identified to be near the CMC [26,32]. Remarkable that, in spite of the high negative charge of the carbon nanotubes, they were unstable in aqueous suspensions in the absence of CTAB [29,30]. At C s = 0 M the nanotubes at C n = 0.003 % formed large visible aggregates and the measured values of PDA ratio were rather large (R  8) ( Fig.…”

Section: Regulation Of Colloidal Stabilitymentioning

confidence: 99%

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A short review on regulation of stability of aqueous suspensions of carbon nanotubes

Manilo¹,

Lebovka²,

Bárány³

2020

Him. Fiz. Tehnol. Poverhni

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This review analyses the authors' recent and related works on electrokinetic properties and colloidal stability of aqueous suspension of multi-walled carbon nanotubes (CNTs) in the presence of surfactants and nanoparticles. Selected adsorptive properties of carbon nanotubes are also considered.The applicability of classical theories of electrophoresis for description of electrophoretic mobility of carbon nanotubes is discussed. Examples on the ζ-potential of CNTs in aqueous suspensions as a function of pH and concentration of electrolytes (KCl, CaCl 2 and AlCl 3 ) are given. Additions of cetyltrimethylammonium bromide (CTAB) cationic surfactant below the critical micelle formation concentration (CMC) values give a reduction and then an overcharging the CNT surface because of accumulation of the surfactant ions in the Stern layer. At concentrations above CMC the substantial drop in ζ-potential is observed. It is due to the shift of the shear plane toward solution as a result of formation of hemi-micelles on the surface. An increase in the mass ratio of artificial mineral Laponite (Lap) in suspension (X) from 0 to 0.4 results in a monotonic decrease of the ζ-potential of CNT + Lap hybrids with reaching its plateau value ≈ -32 mV at X ≥ 0.4 that corresponds to the ζ-potential of "pure" Lap platelets. This evidences the high surface coverage of nanotubes surface with Lap at X ≥ 0.4.The major methods to improve the dispersibility of carbon nanotubes, their colloidal stability and adsorptive properties are briefly discussed, namely: stabilization in mixtures of water and organic solvents; functionalization by chemical treatment; stabilization by additives of surfactants or polymers and hybridization by addition of supplementary stabilizing nanoparticles. CNTs can be significantly debundled in "good" solvents, such as 1cyclohexyl-2-pyrrolidone, N,N-dimethylformamide, or N-methyl-2-pyrrolidone. It is demonstrated that the dispersibility of CNTs is a complex function of the type of surfactant, its concentration and the surfactant/CNTs ratio. The optimum concentration of CTAB to achieve homogeneous aqueous dispersion of carbon nanotubes was identified to be near the CMC. Additions of CTAB significantly modify the size distribution of CNTs and a sharp transition from small primary aggregates to large secondary aggregates at concentrations above CMC is observed. At optimal concentration of Lap the nanotube particles get well stabilized, and a stepwise increase of sedimentation stability is observed.We have shown also that CNT + Lap hybrids can be effectively used for removal of methylene blue dye from aqueous systems. The kinetics and mechanisms of adsorption are elucidated.

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Section: Regulation Of Colloidal Stabilitymentioning

confidence: 89%