Preparation and Evaluation of Some Amide Based Cationic Surfactants as Biocides

In this study, different cationic surfactants were prepared by esterfication of different fatty acids with ethanol then amidation of the prepared esters with N, N dimethyl ethylene diamine then quaternized the tertiary amines with benzyl bromide to produce a series of quaternary ammonium salts (cationic surfactants). Surface tension at four different temperatures of these cationic surfactants was investigated. The surface parameters including critical micelle concentration (CMC), the lowest concentration of surfactants at which micelles are present, maximum surface excess (Γ_max), the number of surfactant molecules at the interface, minimum surface area (A_min) area occupied by each molecule, efficiency (pC₂₀) of surfactant concentration that suppresses surface tension by 20 dyne/cm and surface pressure at CMC (π_CMC), were studied and the thermodynamic parameters such as free energy of micellization (ΔG^o_mic), the work of transfer of surfactant molecules to the bulk of a solution to form micelles and adsorption (ΔG^o_ads), the work of transfer of surfactant molecules from the bulk of a solution to the surface, enthalpy (ΔHo _m) total heat content of the system in micellization process, (ΔH^o_ads) total heat content of the system in the adsorption process and entropy (ΔS^o_m) the degree of disorder in the system in micellization, (ΔS^o_ads) and the degree of disorder in adsorption were calculated. The antimicrobial activity of the prepared surfactants was determined via the inhibition zone diameter against different microorganisms also against sulfate reducing bacteria (SRB) by the dilution method.