Influence of octanohydroxamic acid on the association behavior of cationic surfactants: Hydrolytic cleavage of phosphate ester

Article abstract of DOI:10.1016/j.molliq.2016.06.052

The surface properties and mixed micellization behavior of cetyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TTAB) and dodecyltrimethylammonium bromide (DTAB) with octanohydroxamic acid (OHA) have been investigated by means of conductivity and surface tension measurements in aqueous solution and borate buffer at 300 K. The critical micelle concentration (cmc), surface properties such as maximum surface access (Γ_max), surface pressure at the cmc (Π_cmc) and minimum surface area per molecule (A_min) has been determined. The standard Gibbs free energy of micellization (ΔG_m⁰), standard Gibbs free energy of adsorption (ΔG_ad⁰), and standard Gibbs free energy of micellization per alkyl chain (ΔG_m,tail⁰) of cationic surfactant with OHA have been evaluated. The fluorescence quenching technique was used to estimate the aggregation number (N_agg) and packing parameter (P) for determining the structural feature of cationic surfactants in the presence of octanohydroxamic acid. The hydrolytic reaction of paraoxon with octanohydroxamic acid was studied under a cationic micellar system by using OHA^- at 9.2 pH and 300 K. The variations of surface properties from aqueous medium to the reaction condition have also been discussed. Pseudophase model (PPM) has been fitted for the quantitative treatment of the data.