TY - JOUR
T1 - In situ analysis of alkyl phosphate surfactant adsorption at the alumina/aqueous solution interface
AU - Jeon, Joong S.
AU - Sperline, Roger P.
AU - Raghavan, Srini
AU - Hiskey, J. Brent
N1 - Funding Information:
The authors wish to acknowledge the Arizona Mining and Mineral Resources Research Institute for partial financial support of this work under the US Bureau of Mines grant number Gl114104.
PY - 1996/6/3
Y1 - 1996/6/3
N2 - Both the extent of adsorption and spatial chain orientation of adsorbed alkyl phosphate surfactant molecules on alumina were investigated using an in situ attenuated total reflection-Fourier transform-infrared technique. The adsorption isotherm was characterized by three distinct regions, and adsorption continued to occur even at pH values higher than the isoelectric point of alumina. Upon adsorption of surfactant, the wettability of alumina decreased, followed by a slight increase in the wettability at concentrations greater than 10 ppm, indicating the formation of a second adsorption layer. It was also found that as the surfactant concentration increased, zeta potential reversal occurred, and in a 10 ppm surfactant solution, alumina exhibited negative zeta potentials across the whole pH range. The profile of zeta potential-pH curves was typical for systems involving chemisorption. The spatial alkyl chain orientation angles of the adsorbed surfactant molecules were found to be in the range 48-41° from the normal to the alumina surface for 1-100 ppm surfactant solutions.
AB - Both the extent of adsorption and spatial chain orientation of adsorbed alkyl phosphate surfactant molecules on alumina were investigated using an in situ attenuated total reflection-Fourier transform-infrared technique. The adsorption isotherm was characterized by three distinct regions, and adsorption continued to occur even at pH values higher than the isoelectric point of alumina. Upon adsorption of surfactant, the wettability of alumina decreased, followed by a slight increase in the wettability at concentrations greater than 10 ppm, indicating the formation of a second adsorption layer. It was also found that as the surfactant concentration increased, zeta potential reversal occurred, and in a 10 ppm surfactant solution, alumina exhibited negative zeta potentials across the whole pH range. The profile of zeta potential-pH curves was typical for systems involving chemisorption. The spatial alkyl chain orientation angles of the adsorbed surfactant molecules were found to be in the range 48-41° from the normal to the alumina surface for 1-100 ppm surfactant solutions.
KW - adsorption density
KW - alkyl phosphate surfactant
KW - alumina
KW - attenuated total reflection-Fourier transform-infrared spectroscopy
KW - contact angle
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U2 - 10.1016/0927-7757(95)03489-7
DO - 10.1016/0927-7757(95)03489-7
M3 - Article
AN - SCOPUS:0030567677
VL - 111
SP - 29
EP - 38
JO - Colloids and Surfaces A: Physicochemical and Engineering Aspects
JF - Colloids and Surfaces A: Physicochemical and Engineering Aspects
SN - 0927-7757
IS - 1-2
ER -