The Wettability And Adsorption Of Three Kinds Of Solids By Gemini Surfactants With Hydroxyl And Ester Bond

Wetting solid surfaces by surfactant solutions plays an important role in many industrial processes and daily life, such as flotation, decontamination, oil recovery, coating and deposition. Therefore, it is of theoretical and practical value to study the wettability of surfactant on the solid surfaces. Most studies on the wettability of solid surfaces are focused on aqueous solutions of different single-chain surfactants and mixed surfactants, but are rare on Gemini surfactants. The reported studies showed Gemini surfactants had many superior features such as good water solubility, low critical micelle concentration(CMC), low Krafft point and excellent surface activity compared with conventional single-chain surfactants. Gemini surfactants can not only change the solid-liquid interfacial tension, but also change the structure and composition of the solid surface. It has important application value in the oil exploitation and preparation on coal pitch water slurry.In this paper, a series of biquaternary ammonium salt Gemini surfactants with hydroxyl and ester bond were synthesized in our laboratory. On the basis of the investigation of the surface properties, and the data of the contact angle on PTFE, Paraffin and coal pitch measured by the sessile drop analysis, spreading coefficient and adhesion work were calculated, the wettability and adsorption of Gemini surfactants on the solid surfaces were discussed.The obtained results indicate that the surface tension of Gemini surfactants and the contact angle on PTFE and paraffin decrease with increasing surfactant concentration, and tend to be stable when the concentration exceeds CMC. A linear relationship exists between the adhesive and surface tension of Gemini surfactants with hydroxyl and ester bond on PTFE in a range of certain concentrations. The absorption amount of the surfactant at the liquid-air interface is larger than that at the PTFE-liquid interfaces. In the initial period of adsorption, there is a linear dependence between the adhesional tension and surface tension of 12-2-12 and 14-2-14 on paraffin surface. The changes of adhesion work of Gemini surfactants on PTFE and paraffin surface are similar with the increasing of concentration, which showed the trend of decreasing first and then increasing, and finally tends to be stable. The wettability of Gemini surfactants which have good adhesion on PTFE and paraffin are better. The wetting process of PTFE and paraffin by Gemini surfactants can be generally divided into four phases.The contact angle of Gemini surfactants with hydroxyl on coal pitch surface decreases firstly and then increases with the increase of the length of the hydrophobic chain, the wettability of C12-OH on coal pitch surface is best; the contact angle decreases with the increase of the length of the hydrophobic chain for Gemini surfactants with ester bond, the wettability of m-6-m on coal pitch surface is better than that of m-2-m when the hydrophobic chain length is certain. A linear relationship exists between the adhesive and surface tension of C10-OH、C12-OH and 12-2-12. In addition to 14-6-14, Gemini surfactants are in accordance with the Zisman theory. The wettability of Gemini surfactants with hydroxyl which have good adhesion on coal pitch surface are worse. Zeta potential on the coal pitch surface increases with the increasing of surfactant concentration and finally tends to be stable. Gemini surfactants can change the electrical property and quantity of electric charge on coal pitch surface.