Surface interactions and flotation behavior of calcite, dolomite and ankerite with alkyl hydroxamic acid bearing collector and sodium silicate

- Experiments/DFT simulations to investigate carbonatite gangue minerals flotation.
- Ankerite affinity outperforms calcite/dolomite towards alkyl hydroxamic acid collectors.
- Alkyl hydroxamic acid collector-silicate depressant-carbonatite interactions explained.
- PH effect on collector- depressant-carbonatite interactions revealed.

The surface interactions and adsorption mechanism of alkyl hydroxamic acid bearing collectors and sodium silicate depressant on common carbonatite gangue minerals, including calcite, dolomite and ankerite in flotation were investigated. For this purpose, firstly the flotation behaviors of these minerals in the presence of the collector and depressant were investigated via micro-flotation tests at pH 7-9.5. Meanwhile, the interaction nature of this collector and depressant with minerals was disclosed through FTIR and zeta potential measurements over the studied pH range. It was found that either floatability of minerals in the presence of collector or the affinity of minerals towards collector and depressant adsorption are in the order of ankerite >> calcite dolomite. The nature of collector-minerals' interactions and also the collector's adsorption mechanism were further studied via density functional theory (DFT) simulations to identify the likeliest collector configurations and adsorption pathways of collector and depressant on the mineral surfaces. It was concluded that ankerite has higher affinity towards alkyl hydroxamic acid collector and also sodium silicate as compared with calcite and dolomite. It was revealed that collector is going to interact with metal atoms on the minerals surfaces via covalent bonding through which bridged and monodentate binding configuration are more favorable. It was found that Fe atoms on the mineral surfaces are more involved in bond formation as compared with Ca and Mg. The DFT simulations also indicated that sodium silicate has more affinity towards ankerite which was confirmed via experimental observations. Besides, the surface interaction pathway of both SiO(OH)3− and Si(OH)4 as dominated silicate monomers in aqueous phase on the mineral surfaces were demonstrated. It was found SiO(OH)3− species enable either covalent or hydrogen bonding on the mineral surfaces, while Si(OH)4 species are likely to interact with minerals only through hydrogen bonding. Therefore, SiO(OH)3− species are corroborated to prompt more important depressant effects on froth flotation of carbonatite gangue minerals.

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