Complexes of fluorinated, silicone and hydrocarbon surfactants with carboxymethylcellulose and their influence on properties of the alumina suspension

The aim of this study was to investigate the influence of different types of surfactants on the adsorption, stability, and electrokinetic properties of the carboxymethylcellulose/alumina system as well as the interactions between the surfactants and the polymer. The authors decided to use fluorinated and silicone surfactants besides the conventional hydrocarbon ones. The obtained results showed that carboxymethylcellulose (cmc) adsorption increased in the presence of surfactants due to the formation of polymer-surfactant complexes (the increase of the adsorption from about 0.020 mg m⁻² for pure cmc to 0.030 mg m⁻² for MTAB/cmc and SJ2/cmc mixtures). The obtained complexes of 0.00336% MTAB/cmc and 0.004% S-106a/cmc reduced the surface tension of water more efficiently than pure surfactants of the same concentration (from 70.06 to 62.39 mN/m and 71.06 to 64.26 mN/m respectively). Stability of the alumina suspension was studied as well. The obtained results indicate that the addition of carboxymethylcellulose, surfactants, and the cmc-surfactant complexes leads to the increase of alumina suspension stability. The mechanism responsible for stabilization was electrosteric one. The largest stability was observed for the systems containing the mixture of cmc and surfactants. The reason for this is the formation of the adsorption layer composed of alternately arranged regions of polymer and surfactant complexes. Electrokinetic measurements of the studied systems allowed to describe the structure of the electrical double layer and to determine the point of zero charge of alumina (pHpzc ≈ 7.5). The addition of the polymer as well as surfactants leads to the charge reversal of alumina.

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