Abstract
The adsorption of cationic hexadecylpyridinium bromide and non-ionic oxyethylated octylphenols (TХ-45, TX-100, ТХ-305) surfactants from their mixed solutions at non-porous hydrophobic carbon sorbent such as thermal graphitized carbon black has been studied. The molar fraction of oxyethylated octylphenols in the mixtures was 0.2, 0.4, 0.6, and 0.8. The results have shown that the adsorption values of hexadecylpyridinium bromide depend on the total concentration of the surfactant and the composition of mixtures. It has been found that the molar fraction of nonionic surfactants in the mixed adsorption layers at carbon black surface decreases in the series: ТХ-45 > ТХ-100 > ТХ-305. The regularities of the change in the surface activity of the surfactant mixtures at the solution-solid sorbent interface with an increase in the total surfactant concentration in the solution correlate with those for the solution-air system, but are more pronounced. The areas per hexadecylpyridinium bromide and the oxyethylated octylphenols molecules in the adsorption layer while adsorbing from their binary solutions are lesser than ones for the surfactants adsorption from their individual solutions, and smaller than the corresponding areas at the solution-air interface. These findings indicate the consolidation of the adsorption layer at the solid surface and confirm that the surfactants adsorption at carbon black surface as associates.
Highlights
Adsorption of surfactants at a solid-liquid interface has an important role in many prosesses such as ore flotation, oil extraction, household and personal care applications, in textile, cosmetic, food industries, biotechnology and water treatment [1, 2]
Adsorption of HDPB and Triton X surfactants is due to hydrophobic interactions between alkyl radicals in the surfactant molecules and carbon black (CB) surface
This can be explained by the fact that the inclusion of the molecules of the non-ionic surfactant in the mixed adsorption layer reduces electrostatic repulsion between charged hydrophilic groups of the cationic surfactants and promotes HDPB adsorption
Summary
Adsorption of surfactants at a solid-liquid interface has an important role in many prosesses such as ore flotation, oil extraction, household and personal care applications, in textile, cosmetic, food industries, biotechnology and water treatment [1, 2]. Understanding the main features of mixed adsorption of surfactants at solid surfaces is of vital importance for prediction the properties of the surfactant mixtures and their applications. Adsorption of the surfactants at carbon sorbents is a subject of numerous studies, but majority of the works in this area is devoted to investigation of the surfactant adsorption from single component solutions [4,5,6]. The main research topics related to the surfactants mixtures are the development of theoretical approaches to describe the colloid-chemical interactions between the surfactants in the binary solutions. As for a solid sorbent-solution interface, the studies were conducted mainly with hydrophilic sorbents [10,11,12]
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