Magnetic field effects on surfactants adsorption on the solid surface as regards of its wettability

Abstract

The static magnetic field MF (0.44 T) effects on the adsorption of three surfactants: cationic bromide (DTAB) and hexadecyltrimethylammonium bromide (CTAB), and anionic sodium dodecylsulfate (SDS) from their 10-3 M solutions were studied on bare and low-temperature air plasma treated glass plates. The surface properties of the adsorbed surfactants layers were determined via the water advancing and receding contact angles measurements and then calculation of the apparent surface free energy. An optical profilometer was used to determine the structure and topography of the adsorbed layers. The DTAB and SDS concentrations were below their critical micelle concentration and that of CTAB very close to its cmc. The results showed that in the case of DTAB solution (much below its cmc) a small decrease in the contact angle appeared while in CTAB (close to its cmc) an increase in the contact angle value was observed if adsorbed in the MF presence. Quite good reproducibility of the contact angle values was obtained. This was not the case for the SDS solution where the contact angle values were scattered. The reason was that the anionic surfactant did not adsorb homogeneously on the negatively charged glass surface. The contact angles and the calculated values of the work of water spreading clearly show that MF influences the structure of the surfactant adsorbed layer which was also supported by the optical profilometry images.

Effects of static magnetic field on the surface tension of surfactant solutions

“…It can be postulated that MF causes changes in the structure of the surfactant adsorbed surface layer which last for at least some minutes (so called memory effect) during the time of surface tension measurement. The optical profilometry images of the adsorbed surfactant on the glass surface allow for such the conclusion (Hołysz et al, 2020). The MF influence on the surfactant molecules adsorption on the polar glass surface is also reflected in the changes of water contact angle on the surface (Hołysz et al, 2020).…”

“…The optical profilometry images of the adsorbed surfactant on the glass surface allow for such the conclusion (Hołysz et al, 2020). The MF influence on the surfactant molecules adsorption on the polar glass surface is also reflected in the changes of water contact angle on the surface (Hołysz et al, 2020).…”

“…In the earlier studies on the surfactants (CTAB, DATB, SDS 10 À3 M) adsorption on a microscope glass surface in the absence and presence of the MF (the same way of the MF exposure as above) were also carried out. The results were published and discussed in detail in the paper (Hołysz et al, 2020). Briefly, water contact angles were measured on the dried surfaces and optical profilometry was applied to obtain the information about the structure and topography of the adsorbed layers of the surfactants.…”