The effect of the positions and molecular weight of hydrophilic functional groups of surfactants on gas absorption rates

The purpose of this investigation was to determine the effect of the positions and the molecular weight of surfactant hydrophilic functional groups on the rate of gas absorption.

A quiescent unsteady-state absorption apparatus was used with carbon dioxide and water as the absorption system. Three surfactants with hydroxyl groups were selected for study, namely, n-octanol, 4-octanol and lauryl diglycol amide.

Preliminary absorption tests were made using pure deionized water to determine the diffusion coefficient for the system. A value of 1.93 ± 0.05 x 10⁻⁵ square centimeters per second was obtained. The absorption tests were repeated with the three surfactant solutions at different concentrations. Then the interfacial resistance for each solution was calculated.

The results of the surfactants were compared with each other and were also compared with the results of lauryl diethanol amide previous investigated. The octanol with hydroxyl group at a branched position was found to cause a higher interfacial resistance than those with hydroxyl groups at the end of the hydrophobic chain. It was also concluded that increasing the molecular weight of the hydrophilic group decreased the interfacial resistance.