Dodecylphosphonic acid for the separation of spodumene and albite: Flotation behavior and adsorption mechanism

Spodumene is an important lithium-bearing mineral, that is associated with albite and difficult to separate because of their similar surface chemical properties. Traditional fatty acid collectors often have issues, such as poor selectivity or weak collector ability, and thus developing efficient spodumene collectors is essential. In this study, the phosphonic acid surfactant dodecylphosphonic acid (DDPA) was first used as a single collector for the flotation separation of spodumene and albite, showing good selectivity and collection performance. Then, separation and adsorption mechanisms were studied using various characterization methods, including diffuse reflectance infrared Fourier transform spectroscopy, total organic carbon adsorption measurements, X-ray photoelectron spectroscopy, and zeta potential tests. Flotation tests showed that the recovery for spodumene can reach approximately 80 % through single-mineral flotation under the following conditions: activation without metal ion, neutral pulp pH of 6.5-7.0, and DDPA dosage of 4 x 10-4 mol/L. By contrast, the recovery of albite was only approximately 10 %. The recovery for Li2O in the artificial mixed ore test was 75.03 %, and the grade was 6.30 %. The separation of spodumene and albite was due to the selective adsorption of DDPA on the surface of spodumene, and more DDPA were adsorbed on the surface of spodumene than on albite under the same conditions. Adsorption mechanism analysis indicated that Al and O on the mineral surface were the active sites for DDPA adsorption. Combined with the species distribution, DDPA existed in various forms in different aqueous environments, indicating that DDPA was mainly adsorbed onto the mineral surface through chemisorption and hydrogen bonding. In summary, DDPA can be used as an effective collector for spodumene.