Synergistic collection mechanism of D-phenylalanine and sodium oleate in flotation of diaspore from kaolinite

The chelated absorption and co-adsorption model of D-phenylalanine on diaspore surface. [Display omitted] •An amine acid D-Phe was first introduced as diaspore flotation auxiliary collector.•D-Phe exhibited superior synergistic collection to diaspore against kaolinite.•D-Phe chelated with diaspore surfaces through the amino and carboxylate groups.•The synergism of D-Phe with NaOL involves H-bond interaction and co-adsorption. Mixed collectors were widely used in mineral flotation. In this work, D-phenylalanine (D-phe) was first introduced to improve the collectability and selectivity of sodium oleate (NaOL) for diaspore from kaolinite. The flotation performance of diaspore and kaolinite were studied by micro-flotation tests, and the synergistic mechanisms of D-phe with NaOL were investigated through FTIR spectra, zeta potential, solution chemistry and X-ray photoelectron spectroscopy (XPS). Single and mixed flotation results show that D-phe exhibited superior synergism power with the NaOL collector. Under pulp pH 9.0, the flotation recovery of diaspore was increased from 77.13% to 91.07%, while that of kaolinite was decreased from 16.27% to 13.75%. The zeta potential and XPS analysis indicate that the synergistic mechanisms of D-phe with NaOL were mainly the co-adsorption via the carboxylate group of D-phe and NaOL bonding with the Al sites of diaspore surface. D-phe was chelated onto the diaspore surface through the –COO– and –NH3+/NH2 groups, and the pre-adsorption of D-phe could increase the Al active sites of diaspore surface for the direct adsorption of NaOL. NaOL could also indirectly adsorb on the diaspore surface through H-bonding with –NH2/NH3+ groups of D-phe.