ToF-SIMS as a new method to determine the contact angle of mineral surfaces.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been used as a technique to correlate the surface chemistry of chalcopyrite particles with their contact angle. Three particle sizes (20-38, 75-105, and 150-210 microm) were used, covering a range of contact angles between 20 and 90 degrees. Multivariate statistical techniques were applied to the ToF-SIMS data in order to identify structure in the data and the surface species contributing the most to surface chemistry and hence the hydrophobicity variation. A method to calculate the contact angle of chalcopyrite by ToF-SIMS surface analysis has been developed using only information from three secondary ions: oxygen, sulfur, and a thiol collector fragment. This approach is capable of determining the surface chemistry contribution to the contact angle of individual mineral particles and the distribution of contact angles within a large ensemble of particles. Further measurements verified that the methodology can also be applied to flat surfaces, enabling rapid surface chemistry-hydrophobicity correlations to be made on a wide range of mineral and material systems.