Copper sulfide flotation under acidic conditions using a xanthogen formate compound as collector: Adsorption studies and experimental design approach

Under acidic conditions, isobutyl xanthogen ethyl formate was used as a collector compound in the flotation process for Cu recovery from the mineral bornite (Cu5FeS4). The mineral sample was characterized by X-Ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and X-Ray Photoelectron Spectroscopy (XPS) techniques. Also found in lower proportions were chalcopyrite and quartz. The bornite presented a rough and porous surface. The adsorption study included kinetics, thermodynamics, and isotherm tests. The equilibrium time at pH 2 was 15 min. The kinetics model suggest the adsorption can be described by two processes, both related to the formation of a chelate. Thermodynamically, the collector adsorption process is favored at room temperature, whereas the process is not favored at lower temperatures. The adsorption capacity was 8.8 mg g(-1) achieved by a combination of mechanisms on a heterogeneous surface. Under local optimized conditions, the highest Cu recovery (96.98 %) was determined from an experimental design for an initial collector concentration of 20 mg L-1, a flotation time of 3 min, and pH = 2. Contact time of the collector with the mineral surface represents one of the most important variables in the flotation process. In addition, the combinations between pH-t(f), C-i-t(f), and pH-C-i-t(f) variables have the most significant effect on Cu recovery percentage. The collector can be used satisfactorily at lower pH values. Although the xanthogen formate functional group acted on both the Fe and Cu ions in the mineral, it was observed that the collector has a higher affinity for Cu ions compared with Fe ions.