Co-adsorption of quaternary ammonium compounds—nonionic surfactants on solid–liquid interface

Adsorption of mixed surfactants on the solid substrates has received scant attention in the past. However, in recent times, there have been a few investigations, which have been overviewed. Experimental results of co-adsorption and parallel zeta potential studies using mixed quaternary ammonium compounds CTAB, TTAB and nonyl phenyl ethoxylates (NP13, NP20, NP30) have been reported in this presentation. Three solid substrates, quartz, polystyrene and PTFE were chosen for investigation. ‘S’ shaped adsorption isotherms were obtained in case of all the three substrates. The presence of nonionics had varied effect on the adsorption of CTAB/TTAB depending on concentration. The zeta potential studies, in general, support the adsorption behaviour. However, the change on the solid substrate is influenced predominantly by the positively charged CTAB. Presence of premicellar aggregates on the solid surface is indicated. The nature of solid substrate appears to be of secondary importance.