INTERACTION BETWEEN SODIUM DODECYL POLY(OXYETHYLENE) SULFATE AND ALUMINA SURFACE IN AQUEOUS-SOLUTION

The adsorption of sodium dodecyl poly(oxyethylene) sulfate, SDE(n)S (n = 0, 3, 5, and 8), on positively charged alumina in aqueous solutions of 10 mmol dm(-3) NaCl adjusted to about pH 3.5 has been investigated by measuring adsorbed amount, zeta potential, dispersion stability, E SR, and adsolubilization for yellow OB and 2-naphthol, The adsorption of SDE(n)S increases with decreasing oxyethylene chain length of SDE(n )S, and in particular the adsorption of SDE(8)S is considerably low. T he dispersion of alumina exhibits a dispersion-flocculation-redispersi on process by the adsorption of SDE(n)S, which is well correlated with the change in the zeta potential of alumina. In addition, the ESR spe ctra of 2,2,6,6-tetramethylpiperidinyl-1-oxy(TEMPO) suggest that the m icroviscosity of the adsorbed layer of SDE(n)S is greater than that of the supernatant and that there are two sites for TEMPO in the SDE(3)S , SDE(5)S, and SDE(8)S adsorbed layers. Adsolubilization behaviors of yellow OB and 2-naphthol into the adsorbed layer are markedly affected by the oxyethylene chain length of SDE(n)S; the partition coefficient for yellow OB decreases with increasing oxyethylene chain length of S DE(n)S, but that for 2-naphthol shows the opposite behavior. (C) 1995 Academic Press, Inc.