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The extent of adsorption (Γ₂¹) of cetyltrimethylammonium bromide (CTAB), myristyltrimethylammonium bromide (MTAB), and dodecyltrimethylammonium bromide (DTAB) from aqueous solution onto a cellulose−water interface has been measured analytically in a wide range of surfactant concentrations below and above the critical micelle concentration (cmc) at different physicochemical conditions and in the presence of different electrolytes and urea. Γ₂¹ is found to increase with increase of bulk surfactant concentration C₂ until it reaches a maximum value Γ₂^m when C₂ reaches a critical value, C₂^m. With further increase of C₂ beyond C₂^m, Γ₂¹ decreases from Γ₂^m and becomes zero with attainment of surface azeotropic state at a surfactant concentration C₂^azeo. For C₂ > C₂^azeo, values of Γ₂¹ are negative due to the excess hydration of cellulose fibril and desorption of surfactant micelles from the surface to the …