Determination of the adsorption isotherm
The adsorption isotherm of DBSA with 0.15M NaCl
at pH 4 on cotton fabric was obtained by exposing a
1.2-g piece of the cotton fabric to 30 mL of the surfactant
solution of known initial concentration. The
adsorption was allowed to take place at 308C for 15 h in a 36-mL vial. The amounts of DBSA in the
supernatant were measured by a UV spectrophotometer
(Shimadzhu Model UV 2550) at 224 nm. The initial
DBSA concentrations in these experiments were
varied from 10 to 10,000 lM which covered the
regions below and above the critical micelle concentration
(CMC) of DBSA. A plot of the amount of
adsorbed surfactant versus equilibrium supernatant
concentration yielded the surfactant adsorption isotherm.