Selective Flotation of Cassiterite from Calcite with Salicylhydroxamic Acid Collector and Carboxymethyl Cellulose Depressant

Advancing phosphate ore minerals separation with sustainable flotation reagents: An investigation into highly selective biobased depressants

Froth flotation has been a commonly employed technique to enrich natural ores by removing impurities based on the surface properties of minerals. This process involves the use of various reagents, including collectors, depressants, frothers, and activators, which are often chemically synthesized and may represent environmental risks. Therefore, there is a growing need to develop biobased reagents that offer more sustainable alternatives. The aim of this review is to provide a comprehensive assessment of the potential of biobased depressants as a sustainable alternative to traditional reagents in selective flotation process for phosphate ore minerals. To achieve this objective, the review investigates the extraction and the purification methods of different biobased depressants, analyzes the specific conditions for reagent interaction with minerals, and assess the biobased depressants' performance through a range of fundamental studies. These studies aim to (i) provide a better understanding of the adsorption behavior of some biobased depressants onto the surfaces of apatite, calcite, dolomite, and quartz comprised in different mineral systems by measuring their zeta potential and analyzing their Fourier transform infrared spectra before and after contact with these reagents, (ii) determine the depressants' adsorption amounts, (iii) evaluate their effect on the contact angle of bare minerals, and (iv) assess their ability to inhibit the flotation of the studied minerals. The outcomes revealed the potential use and the promising applicability of these unconventional reagents since their performance is comparable to that of conventional reagents. In addition to their good effectiveness, these biobased depressants have the added advantages of being cost effective, biodegradable, non-toxic, and ecofriendly. Nevertheless, further research and investigations are required to improve the selectivity and, consequently, the effectiveness of biobased depressants.

Interface Interaction of Benzohydroxamic Acid with Lead Ions on Oxide Mineral Surfaces: A Coordination Mechanism Study

Surface coordination chemistry is important in areas such as adsorption, separation, and catalysts. In this work, surface coordination interactions of benzohydroxamic acid (BHA) with the lead ion [Pb(II)] adsorbed on the cassiterite surface have been investigated by first-principles calculations due to its great significance in froth flotation. Cluster calculations show that BHA possesses the weakest chelation with Pb(II) due to the electron withdrawal ability of the benzyl ring in comparison with other hydroxamic acids. Pb(II) thermodynamically prefers to react with the cassiterite surface rather than BHA. On the other hand, the partial density of states and the atomic overlap populations have consistently verified that the adsorption of BHA results in a better symmetry in electron densities than the hydrated Pb(II). The electron density maps and the electronic localization functions have further visualized the rearrangement of the 6s² lone pair around the lead atom. It can be concluded that the surface coordination mechanisms of Pb(II) on oxide minerals can be attributed to the coordination ability of BHA and the unique electronic structure of Pb(II), which accounts for the reported better flotation performance of the pre-assemble strategy than the pre-activating approach. This work sheds some new light on the unique coordination activation mechanism of metal ions on oxide mineral surfaces. It should be instructive to design and screen new environment-friendly flotation reagents and flotation flowsheets.

Probing the Interaction Mechanism between Benzohydroxamic Acid and Mineral Surface in the Presence of Pb2+ Ions by AFM Force Measurements and First-Principles Calculations

Probing the interaction mechanism between organic molecules and material surfaces in the presence of metal ions is of great importance in many fields, such as mineral flotation. The collectability of benzohydroxamic acid (BHA) to a spodumene (LiAl(SiO₃)₂) mineral surface during mineral flotation could be enhanced with the addition of metal ion activators-Pb²⁺ ions. Pb²⁺ ions could be added as either Pb-BHA complex formed by premixing Pb²⁺ ions and BHA molecules at a given ratio or sequential addition of Pb²⁺ ions and BHA molecules. However, the complete understanding of the interaction mechanisms (e.g., adhesion) between BHA and the spodumene mineral surface in the presence of Pb²⁺ ions remains very limited. In this study, atomic force microscopy (AFM) was used to measure the intermolecular forces between BHA and the spodumene mineral surface in aqueous solutions. A BHA model molecule, that is, N-hydroxy-4-mercaptobenzamide (MBHA), was synthesized to prepare a BHA-functionalized AFM probe for force measurements. Two model systems (i.e., a Pb-BHA complex interacting with the spodumene mineral surface (model I) and BHA with a Pb²⁺-activated spodumene surface (model II)) were investigated for comparing the role of Pb²⁺ in BHA-mineral adhesion. The adhesion measured for model I (23.7 mN/m) is much higher than that of model II (12.5 mN/m), as further supported by the adsorption energies obtained from density functional theory (DFT) calculations. The calculation results showed a higher adsorption energy for model I (∼188.58 kJ/mol) than model II (∼128.16 kJ/mol), which is due to the better spodumene flotation recovery for the Pb-BHA complex as a collector than the sequential addition of Pb²⁺ and BHA. This work provides useful information on the intermolecular interactions between chemical additives and mineral surfaces in complex mineral flotation processes, and the methodology can be readily extended to other related interfacial processes such as membrane technology, water treatment, oil production, and bioengineering processes.

New Combined Depressant/Collectors System for the Separation of Powellite from Dolomite and the Interaction Mechanism

The flotation beneficiation of powellite from dolomite was achieved with a new reagent system that consists of a mixed collector of sodium oleate (NaOl) and benzohydroxamic acid (BHA) and a depressant sodium hexametaphosphate (SHMP). The interaction mechanism of the reagent regime with minerals was studied using zeta potential and X-ray photoelectron spectroscopy (XPS) detection together with crystal chemistry and interaction energy analysis. The matching features of O–O distance in BHA with that in saline minerals and active site density/activity were used as methods to explain the reagent/mineral interaction. The results of microflotation finally established the new reagent regime at pH 8–12: 2.5 × 10−4 M SHMP, 2 × 10−4 M mixed collector containing 1.5 × 10−4 M NaOl and 0.5 × 10−4 M BHA. SHMP selectively depresses the adsorption of NaOl and BHA onto dolomite but minimally affects the adsorption of NaOl and BHA on the powellite surface.

Selective Flotation of Pyrite from Galena Using Chitosan with Different Molecular Weights

Pyrite is a major gangue mineral associated with galena and other valuable minerals, and it is necessary to selectively remove pyrite to upgrade the lead concentrate by froth flotation. In this study, the flotation experiments of a single mineral and mixed minerals were performed using chitosan with different molecular weights (MW = 2−3, 3−6, 10 and 100 kDa) as a depressant, ethyl xanthate as a collector, and terpineol as a frother, in a bid to testify the separation of pyrite from galena. Flotation results showed that the selective flotation of pyrite from galena can be achieved under the preferred reagent scheme, i.e., 400 g/t chitosan (10 kDa), 1600 g/t ethyl xanthate, and 100 g/t terpineol, while chitosan with other molecular weights cannot. Furthermore, the results of the zeta potential and contact angle measurements revealed that chitosan (10 kDa) has a strong adsorption on galena yet a very weak adsorption on pyrite at the dosage of 400 g/t. This study showed that chitosan (10 kDa) has great potential in the industrial flotation separation of pyrite from lead concentrates.