The study investigated the influence of molecular structures of alkanols on the adsorption behaviour, which underpins the performance of these chemicals as frothers in mineral floatation. The adsorption isotherm of hexanols and octanols at air/water interface was determined using Du Nouy ring method, in combination with an automatic dispenser. It was found that Frumkin isotherm can describe the adsorption behaviours of all investigated surfactants. However, the adsorption parameters varied significantly with the structure and length of hydrophobic tails. The relationship between molecular structures and interactions of adsorbed molecules was also discussed.