In situ adsorption of mixed collectors BHA/DDA in spodumene-feldspar flotation system

Herein, benzohydroxamic acid/dodecylamine (BHA/DDA, optimal molar ratio of 6:1) demonstrated the excellent separation in the flotation of spodumene (ca. 88% recovery) from feldspar (ca. 24% recovery) at pH 8-9. To detect the underlying mechanism, in-situ attenuated-total-reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy with two-dimensional correlation spectroscopy (2D-COS), zeta potential measurements, in-situ microcalorimetry, and X-ray photoelectron spectroscopy (XPS) were performed. In-situ microcalorimetry results indicated that the mixed collector released more heat than the individual collectors for both minerals. Moreover, The order of the difference in the adsorption reaction heat between this two minerals is as follows: vertical bar Delta Q vertical bar(BHA/DDA) (13.948 J.g(-1))>vertical bar Delta Q vertical bar(DDA) (3.116 J.g(-1))> vertical bar Delta Q vertical bar(BHA) (1.110 J.g(-1)), confirming the excellent separating ability of mixed collector. In-situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and two-dimensional correlation spectroscopy (2D-COS) sequences results showed that the sorption process and configuration of BHA/DDA (0.4 mM, molar ratio = 6:1) on spodumene and feldspar surfaces were different at pH of 4-5 and 8-9, mainly due to the different BHA structure and the formation of hydrogen bond between BHA and DDA at different pH range. Zeta-potential and X-ray photoelectron spectroscopy (XPS) also suggested that their prominent separation is not simply due to the higher adsorption density for a single collector in the presence of mixed collector. Lastly, recommended adsorption models for the adsorption of the complex on the surfaces of spodumene and feldspar were proposed. This work provided powerful in-situ detection technologies to reveal the reagent-solid interaction in selective separation processes.