Adsorption of Surfactants on Carbon Black‐Water Interface

Abstract

Carbon black dispersions are prepared using anionic, cationic, and nonionic surfactants as dispersants in aqueous medium and adsorption behavior of these surfactants is studied along with wettability and stability. Adsorption isotherms for all the surfactants are shown to be of Langmuir type except for lauryl dimethybenzyl ammonium chloride (BKC) where the amount adsorbed increases with increase in the concentration of BKC. Out of the two anionic surfactants used [sodium dodecyl sulphate (SDS) and sodium dodecylbenzene sulphonate (SDBS)], SDBS showed higher adsorption, wettability and stability. Among cationic surfactants viz. cetyltrimethyl ammonium bromide (CTAB), cetylpyridinium chloride (CPC), BKC and Stertile, stertile showed better adsorption. In the case of nonionic surfactants viz. nonylphenol ethoxylates (NP 20 and NP 40) and Triton X‐100, the maximum amount of surfactant adsorbed decreased in the order NP 40 < NP 20 < Triton X‐100. Stability of the dispersion improved in the same order. Addition of salt resulted in increase in both effectivenss and efficiency of the ionic surfactant adsorbing on the carbon black surface while the stability decreased. Pretreatment of carbon black surface with triethanolamine had negligible effect on the adsorption behavior of non ionic surfactants but the wettability and stability improved.