A comparative study of the adsorption mechanisms of an amine thioacetate collector (Armac C) and the well-known amyl xanthate collector on pyrite is presented in this paper. These results allowed a better understanding of the behavior of these two collectors during pyrite flotation. The adsorption isotherms were constructed both at natural pH and alkaline pH (pH = 11). Colorimetric technique was used to measure both Armac and xanthate concentration in solution. The effect of the pH regulator types was taken into account by testing soda ash (NaOH) and hydrated lime Ca(OH)(2)- Xanthate collector adsorbs onto pyrite surfaces in the form of amyl dixanthogen and can be detected on pyrite surface using diffuse reflectance infrared Fourier transform (DRIFT) when the statistical surface coverage (0) was greater than 0.9. Xanthate affinity towards pyrite decreases at alkaline pH and the depressant role of the hydrated lime is greater than the one of soda ash. The adsorption isotherms allowed us to notice the Armac affinity for pyrite at alkaline pH levels. Contrary to the KAX effect, the Armac seems to be indifferent to the type of pH regulator. Even if Armac molecules are detected at a statistical surface coverage greater than 0.3, hydrophilic functionalities (-C-C=S, -CNH- and -COH) are only observed for theta > 12. No information was obtained on the adsorption mechanisms in the monolayer capacity. Finally, flotation tests on sulphidic mine tailings were conducted. Armac gave the best results for cyanide bearing tailings compared with KAX even after cyanide destruction, washing and sulphide activation. The obtained results corroborate the findings from the pure pyrite sample study. (C) 2004 Elsevier Ltd. All rights reserved.