Characterization of wettability alteration of calcite, quartz and kaolinite: Surface energy analysis

The paper addresses wettability alteration of calcite, quartz and kaolinite powders, with stearic acid (SA), N,N-dimethyldodecylamine (NN-DMDA) and asphaltene as oil soluble additives. It is a challenge to convert silicate based mineral surfaces from strongly water-wet to more oil-wet. Thermogravimetric analysis (TGA) of the modified powders is used to quantify the monolayer adsorption and is suggesting the possible molecular orientation on the mineral surfaces. Characterization of the mineral surface hydrophilicity/hydrophobicity due to modification is determined by the enthalpy of the water vapor adsorption isotherm. From the quantity and the affinity to water vapor adsorption, a new wettability index is suggested. The enthalpy of water adsorption relative to liquefaction enthalpy shows that stearic acid and asphaltene deeply modify the calcite toward more oil-wet for treated humidified surfaces. It is interesting to observe that although the presence of a water film on quartz and kaolinite surfaces, enhance the adsorption of N,N-dimethyldodecylamine (NN-DMDA), does not eliminate but reduces the asphaltene adsorption.

Microcalorimetry set up used for water vapor adsorption enthalpy to determine hydrophilicity/hydrophobicity of modified mineral surfaces.Figure optionsDownload as PowerPoint slideHighlights
► Investigation of wettability alteration of different minerals, with SA, NN-DMDA and asphaltene.
► Investigation of the effect of water film on adsorption of SA, NN-DMDA and asphaltene over minerals.
► Developed an approach to determine the wettability index by water vapor adsorption isotherm.
► Estimation of possible molecular orientations of organic adsorbates on the mineral surfaces, interpreted from TGA data.