The inhibiting effect of Pb-starch on chlorite flotation and its adsorption configuration based on DFT computation

Chlorite is widely associated with the valuable oxidized minerals, and the inhibition of chlorite is an inevitable problem during flotation separation. This study finds the Pb-starch is the effective depressant for the chlorite flotation to selectively decrease the flotation rate and recovery. The zeta potential of chlorite surface also increases with the treatment with Pb-starch, which keeps increasing with the increase of lead nitrate dosage. Meanwhile, the FTIR spectra determine the effect of starch and Pb-starch is chemisorption, and the XPS measurement confirms the functional group of starch is hydroxy while that of Pb-starch is Pb-O group. Furthermore, the bulk cell structure of chlorite is optimized, including hydroxyl-terminated surface and silica-terminated surface. The adsorption configuration is established in terms of the DFT computation, and the optimal configuration with the lowest adsorption energy is the glucose-Pb2+ complex adsorbing on the silica-terminated surface through the three covalent bonds of Pb2+ and O atoms. The partial density of states of this configuration confirms the bonding of Pb2+ with O atoms is the hybrid of Pb-6s,Pb- 6p and O-2p, and the electronic property analysis confirms the Pb2+ ion provides empty orbits to accept the electrons from O atoms on the silica-terminated chlorite surface.

Automated summary

This study found that Pb-starch is an effective depressant for chlorite flotation, selectively decreasing its flotation rate and recovery. The zeta potential of chlorite surface increases with the treatment of Pb-starch, and this increase is proportional to the dosage of lead nitrate. Using FTIR spectra and XPS measurement, it was determined that starch and Pb-starch chemisorb onto chlorite, with the functional group of starch being hydroxy and Pb-starch being Pb-O group. Additionally, the optimal adsorption configuration was determined through DFT computation, with the glucose-Pb2+ complex adsorbing on the silica-terminated chlorite surface through three covalent bonds of Pb2+ and O atoms.