Study On The Adsorption Characteristics Of Anionic Surfactants On The Surface Of Clay Minerals

The adsorption characteristics of anionic surfactants on the surface of clay minerals(kaolinite,montmorillonite,illite)and the mechanism of adsorption on the surface of clay minerals can be used to optimize the compound system of fracturing fluid and provide theoretical guidance for the fracturing of clay layer during fracturing.The related parameters of anionic surfactants were measured by surface tension method and viscosity test,such as sodium alkyl sulfate(SDS)and twelve alkylbenzene sulfonate(SDBS).And SDBS was selected as experimental anionic surfactants.Then the distribution characteristics of the adsorption capacity of anionic surfactants on the surface of clay minerals were studied by ultraviolet spectrophotometry and agitation adsorption method.The adsorption kinetic characteristics of clay minerals at different concentrations were obtained by the adsorption kinetic model.XRD,FTIR,SEM+EDS,Zeta potential and cryogenic liquid nitrogen sorbent were used to characterize the interlayer structure,functional groups,surface morphology and pore size distribution of different clay minerals before and after adsorption of surfactants and study on the adsorption mechanism of different clay minerals.The results show that: The critical micelle concentration of SDS and SDBS at 25? was 0.008mol/L and 0.002mol/L,The surface tension and half life of the two kinds of surfactants were exponentially decreased with the increase of temperature,the viscosity was decreased linearly with the increase of temperature.It was calculated that the activation energy of SDBS viscosity was higher than that of SDS,and SDS was more likely to be micellization than SDBS.The adsorption curves of three kinds of clay minerals to anionic surfactants were similar.And the higher the concentration of the surface active agent,the higher the adsorption capacity of the same clay minerals.In the process of adsorption of the same concentration surfactants,the equilibrium adsorption capacity was that: Montmorillonite > illite > kaolinite.Three kinds of clay minerals were all satisfied by the pseudo two class adsorption kinetic model and adsorption type was chemisorption.Montmorillonite was dominated by inks and small cylindrical pores;Illite was dominated by a closed form at one end;Kaolinite was dominated by parallel interplate holes.Surface area distribution was that: Montmorillonite > illite > kaolinite.The XRD test was found that: the interlayer space of montmorillonite was changed,but the illite and the kaolinite were not changed.The maximum adsorption amount of Montmorillonite was determined by the maximum surface area and interlayer adsorption.There was no interlayer adsorption for illite and kaolinite.The specific surface area of kaolinite was smaller than illite,and the amount of adsorption was small with Illite.The chemical adsorption of the three clay minerals was further confirmed by SEM,EDS and FTIR.The adsorption of anionic surfactants in clay minerals was the result of the interaction of electrostatic repulsion and hydrophobic forces by Zeta potential test.This study provides a theoretical support for the combination and optimization of the foam fracturing system in the clay fracture.