Question

Effect of temperature on cmc of gemini surfactants

Answer 1

Answer:The corrosion inhibition characteristics of the synthesized cationic gemini surfactants, namely bis(p-(N,N,N-decyldimethylammonium bromide)benzylidene thiourea (10-S-10), bis(p-(N,N,N-dodecyldimethylammonium bromide)benzylidene thiourea (12-S-12) and bis(p-(N,N,N-tetradecyldimethylammonium bromide)benzylidene thiourea (14-S-14) on the carbon steel corrosion in 1 M hydrochloric acid have been investigated at 25 °C by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The inhibition efficiencies obtained from all methods employed are in good agreement with each other. The obtained results show that compound 14-S-14 is the best inhibitor with an efficiency of 97.75% at 5 × 10−3 M additive concentration. Generally, the inhibition efficiency increased with increase of the inhibitor concentration. Changes in impedance parameters (charge transfer resistance, Rct, and double-layer capacitance, Cdl) were indicative of adsorption of 14-S-14 on the metal surface, leading to the formation of a protective film. The potentiodynamic polarization measurements indicated that the inhibitors are of mixed type. The adsorption of the inhibitors on the carbon steel surface in the acid solution was found to obey Langmuir’s adsorption isotherm. The free energy of adsorption processes were calculated and discussed. The surface parameters of each synthesized surfactant were calculated from its surface tension including the critical micelle concentration (CMC), maximum surface excess (Γmax) and the minimum surface area (Amin). The free energies of micellization (ΔGomic) were calculated. The surface morphology of carbon steel sample was investigated by scanning electron microscopy (SEM).

Explanation:

Answer 2

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The CMC values of cationic gemini and monomeric surfactants increase with increasing percentage of polymers. The CMC and α values of cationic surfactant increased with increasing temperature. The values of ( Δ G m ° ) are negative in all cases and indicate that the micelle formation process is spontaneous.