Flotation Recovery Research Articles

Insights into flotation separation mechanism of chalcopyrite from galena using mercaptosuccinic acid as a novel depressant: Experimental and MDS studies

The separation of polymetallic sulfide ores by flotation is a difficult task in the mineral processing industry. In this investigation, a small-molecule organic compound, mercaptosuccinic acid (MSA), was used as a new depressant for inhibiting galena in chalcopyrite flotation. Micro-flotation and surface wettability tests indicated that MSA pronouncedly weakened the floatability of galena but not chalcopyrite, resulting in marked differences in their flotation recovery. Findings of Fourier transform infra-red (FT-IR) spectroscopy measurements and reagent adsorption trials showed that MSA was strongly adsorbed on galena, resulting in the inability of the collector to effectively interact with galena. Atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) analyses further corroborated that MSA showed a greater affinity for galena than chalcopyrite, this behavior markedly altered the superficial chemical environment of galena. Molecular dynamic simulations (MDS) showed that MSA increased the concentrations of H2O molecules on galena, which enhanced the surface hydrophilicity of galena.

Synergism mechanism of the combined NaOL-SDBS collector at solid-liquid interface and its response to flotation separation of ilmenite from pyroxene

Recovering ilmenite efficiently through froth flotation is challenging. In this research, a novel binary system of sodium oleate (NaOL) and sodium dodecyl benzene sulfonate (SDBS) was applied to promote the flotation performance of ilmenite. Using a total dosage of 90 mg/L combined NaOL-SDBS (4:1) collector, the highest flotation recovery rate of ilmenite was 91.55% at pH 5.0. Furthermore, the artificially mixed ore tests produced a concentrate with a TiO2 grade of 43.55% and a TiO2 recovery of 84.07%, confirming the promising separation performance of the combined collector. Results indicated positive synergism between NaOL and SDBS in ilmenite flotation. The synergism of the binary collector at the solid-liquid interface was identified by the analyses of adsorption amount, contact angle, surface tension, atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). Insights into the synergistic effect between NaOL and SDBS on the ilmenite flotation were mainly attributed to a significant decrease in the surface tension of solid-liquid interface, and the strong adhesion forces of co-adsorption between the combined NaOL-SDBS collector and the mineral surface.

Insight into the Effect of Nanobubbles on Fine Muscovite Powder Flotation in Different Dodecylamine Concentrations and Stirring Intensities: Kinetics and Mechanism

Flotation-introduced nanobubbles were expected to be an efficient and economical method to recover fine muscovite. This study aimed to explore the mechanism of the change appearing in flotation after introducing nanobubbles through micro-flotation, particle vision and measurement, flotation kinetics, and induction time measurement. The results of micro-flotation, which respectively feed muscovite or muscovite pretreated with nanobubbles in different concentrations of dodecylamine (DDA), were fitted with four flotation kinetic models using Origin. Different methods were used to examine how the introduction of nanobubbles affected the flotation process. The results showed that nanobubbles improved both the flotation rate and recovery of muscovite. Nanobubbles played different roles in different stirring intensities. At low stirring intensity, nanobubbles did not perform well. In suitable stirring intensity, nanobubbles helped particles aggregate and improved the collision probability between bubbles and minerals. However, at high stirring intensity, shear forces caused by ultra-high fluid velocities could disrupt particle aggregation.

The role of interfacial nanobubbles in the flotation performance of microfine particles

The enhanced role of Interfacial nanobubbles (INBs) in microfine particles flotation is still unclear. In this study, the microfine particles with different sizes were functionalized to obtain different wettability. The temperature difference method was employed to produce the nanobubbles water. Atomic force microscopy (AFM) was utilized to investigate the formation of INBs. A temperature-controlled flotation system was devised to investigate the flotation performance of microfine particles in the presence and absence of INBs. Agglomeration experiments and attachment time tests were conducted to elucidate the enhanced effects of INBs on flotation from the perspectives of particle-particle and bubble-particle interactions. The results showed that both the number and size of INBs increased with the increase of surface hydrophobicity and level of air saturation in water. In the temperature-controlled flotation system, the flotation recovery and flotation rate of microfine particles were improved significantly in nanobubbles water compared to that in normal water. The optimal flotation result of −38 μm strongly hydrophobic particles was obtained in nanobubbles water at 25 ℃. The enhanced impact of INBs on flotation was more pronounced for more hydrophobic particles. The increase in the apparent size of particles and reduction in particle-bubble attachment time facilitated by INBs contributed to the flotation performance of microfine particles. This study underscores the pivotal effect of INBs on the flotation of microfine particles through enhancing particle-particle and bubble-particle interactions.

The selective flotation separation of apatite from dolomite and calcite utilizing a combination of 2-chloro-9-octadecenoic acid collector and sodium pyrophosphate depressant

In apatite flotation, oleic acid is a commonly used fatty acid collector but is limited by its selectivity and solubility. Acknowledging the reactivity of the α-C atom within oleic acid molecular structure, this study introduces a Cl atom at this site, leading to the synthesis of a novel collector, 2-chloro-9-octadecenoic acid (2-Cl-9-ODA). This collector is utilised in the flotation separation of apatite from its associated carbonate gangue minerals, dolomite and calcite. Flotation experiments reveal that the application of 2-Cl-9-ODA collector, in conjunction with sodium pyrophosphate (NaPP) inhibitor, facilitates the effective separation of these three minerals. Analysis on these mineral surface solubilities, augmented by NaPP, illustrates a solubility sequence: calcite surpasses dolomite, which marginally exceeds apatite. Interestingly, this sequence inversely matches the flotation recoveries, suggesting the superior recoveries of apatite over dolomite and significantly over calcite. The inhibition effect of NaPP on dolomite and calcite flotations is inferred to associate closely with the scarcities of the surface Ca2+ ions. Moreover, adsorption quantity and zeta potential experiments indicate that NaPP depressant significantly reduces the adsorption amounts of 2-Cl-9-ODA on dolomite and calcite surfaces, while barely affecting its adsorption on apatite. First-principles calculations show that the Cl atom introduction allows 2-Cl-9-ODA collector to adopt a parallel adsorption configuration on the mineral surfaces, decreasing its collecting abilities. This research offers theoretical underpinnings for the industrial use of 2-Cl-9-ODA collector in apatite flotation and delivers key understandings for the advancement of groundbreaking apatite flotation collectors.

Flotation behavior and mechanism of microfine apatite and illite in different electrolyte solution systems

The deep sea is rich in mineral resources, and due to the scarcity of freshwater resources, the use of seawater is becoming more widespread. However, the presence of a large number of electrolyte ions in seawater can pose a challenge to mineral flotation and the effects of different electrolytes vary. This study investigated the effects of common chloride (Cl-) electrolyte solutions of Na+, Mg2+ and Ca2+ on the flotation behavior of microfine apatite and illite using sodium oleate (NaOL) as the collector and acidified sodium silicate (ASS) as the depressant. The results showed that ASS can selectively adsorb to the surface of illite as Si(OH)4, hindering the action of NaOL but having little effect on apatite. The electrolyte solution improved the foaming performance of the slurry. It also reduced the critical micelle concentration (CMC) of NaOL and promoted the formation of NaOL micelle, which promoted the adsorption of NaOL on the surface of apatite. However, the reaction of free Mg2+ and Ca2+ in the slurry with oleic anion consumed the effective components of the collector, which was not conducive to mineral flotation. After NaOL interacted with apatite, it had hydrophobic agglomeration effect, which strengthened the flotation recovery of microfine apatite and the separation efficiency from illite.

Co-modification of chrysocolla with ammonia and 1,2-diaminopropane and its response to flotation

Chrysocolla is a typical copper oxide with unique structural characteristics and a variable chemical composition, which make its recovery by flotation considerably challenging. A novel ammonia-1,2-diaminopropane-xantahte (NH3·H2O-1,2-DAP-xanthate) flotation method was proposed in this study for its effective recovery. Compared with the 1,2-DAP-xanthate system, the recovery of chrysocolla was substantially increased from 73.43 % to 95.26 % using the NH3·H2O-1,2-DAP-xanthate system. X-ray photoelectron spectroscopy, zeta potential, Fourier transform infrared spectroscopy, xanthate adsorption capacity, and time-of-flight secondary ion mass spectrometry analyses showed that the increase in the chrysocolla flotation recovery was attributed to an increased in the effective xanthate adsorption on the chrysocolla surface. The additional adsorption of xanthate could be attributed to the alteration of the surface properties of the chrysocolla by NH3·H2O, which exposed more copper sites and reduced the hydrophilic component of the surface. This promoted the effective adsorption of more 1,2-DAP on the mineral surface. Thus, more chelated copper formed, which improved the mineral surface activity and increased the number of active sites interacting with the xanthate.

Highly efficient flotation of ilmenite with a novel dithiocarbamate-hydroxamate collector

The pre-activation of lead nitrate has been extensively proved to be an effective technique in ilmenite flotation, and sodium oleate is the preferred collector. Realization the clean flotation of ilmenite is an important aspect to respond the green and low-carbon policy. In this work, a dithiocarbamate-hydroxamate collector OAHD was pioneeringly added into the direct flotation of ilmenite as an efficient collector. The micro-flotation performance found that OAHD realized an efficient flotation of ilmenite under low concentration of 1.0 × 10−5 mol/L under around pH 8.0, and the flotation recovery rate of ilmenite reached about 94.2%, which was about 35.8% higher than that of NaOL. The morphology of ilmenite observed by AFM probed the self-assemble adsorption behavior of OAHD on ilmenite surface. DFT (density functional theory) calculations suggested that both dithiocarbamate and hydroxamate groups are the chemical active centers and have strong electron acceptability of d-orbital electrons of Fe atoms at/on the interface of ilmenite. UV–Vis spectra demonstrated that dithiocarbamte and hydroxamate groups simultaneously has strong chemical reaction with Fe2+ ions. XPS analysis recommended that OAHD chemisorbed on ilmenite surface to produce the surface Fe(II)-OAHD complexes where the O,O-five membered ring of Fe(II)-hydroxamate compounds were formed.

Effect of lead ions treatment on the flotation behavior of lime-depressed pyrite in a butyl xanthate system

Pyrite is often found alongside other sulfide minerals and is typically suppressed by lime during industrial flotation to selectively enrich with other valuable minerals. Given the continuous depletion of mineral resources, recycling these suppressed resources has become necessary. Consequently, the reactivation of lime-depressed pyrite is crucial for its recovery via flotation. This study investigated the lead (Pb) nitrate to activate lime-depressed pyrite. Various analytical techniques, including micro-flotation tests, zeta potential measurements, contact angle measurements, ultraviolet–visible spectrophotometry, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM-EDS) were employed to investigate the activation mechanism of Pb2+ on lime-depressed pyrite. The treatment with Pb2+ resulted in a significant enhancement in the recovery of lime-depressed pyrite flotation, achieving a maximum recovery of 98.33 %. Analysis through zeta potential, XPS, and SEM-EDS revealed that Pb species reacted with lime-depressed pyrite surfaces to form Pb-S and Fe-O-Pb species. This reaction enhanced the active sites and adsorption of collectors on lime-depressed surfaces, consequently increasing the hydrophobicity of the pyrite particles.

Study on the effects of a novel imidazoline siliconophilic collector in the desilication process of magnesite: Separation experiments, adsorption mechanisms, and separation model

This study innovatively introduced heptadecenyl amine ethyl imidazoline quaternary ammonium salt (ODD) as a siliconophilic flotation collector, effectively facilitating the achievement of high-efficiency separation of magnesite from quartz. ODD exhibits unique properties such as high selectivity and environmental friendliness. Through a comprehensive series of experiments, including flotation tests, zeta potential characterization, atomic force microscopy (AFM) imaging, Fourier-transform infrared (FTIR) spectroscopy, and time-of-flight secondary ion mass spectrometry (ToF-SIMS), the flotation performance and selective adsorption mechanisms of ODD were thoroughly investigated. The experiments demonstrated that at a pH of 7.00 and an ODD concentration of 40 mg/L, quartz achieved a flotation recovery rate of 95.16 %, while magnesite was only 2.99 %, underscoring the high selectivity of ODD in mineral separation. Zeta potential measurements indicated that ODD exhibits strong adsorption interactions with quartz over magnesite. AFM observations confirmed that ODD forms significant adsorption structures on quartz surfaces, in contrast to weaker interactions with magnesite. FTIR analysis further revealed the robust interactions between ODD and quartz through hydrogen bonds and electrostatic forces, which were significantly diminished on magnesite surfaces. ToF-SIMS analysis provided direct evidence of ODD’s selective adsorption on quartz, contributing to a better understanding of the flotation mechanisms involved. This research not only offers a novel approach for the purification of magnesite and effective removal of quartz but also demonstrates the potential of ODD as an eco-friendly collector in mineral processing, potentially advancing a green transformation in the industry. The findings provide a solid theoretical and experimental basis for future industrial applications and innovative development of flotation collectors.

A self-assembled surfactant for efficient flotation of cassiterite: Experimental study and DFT calculation

Surfactants of different kinds are important in the flotation of metal oxide ores. In this paper, a combined organic surfactant was formed through self-assembly of salicylhydroxamic acid (SHA) and isopropanolamine dodecylbenzenesulfonate (DBIA). The effects of SHA and DBIA on the flotation behavior of cassiterite were investigated. Density functional theory (DFT) calculations were used to clarify the microscopic adsorption mechanism of SHA and DBIA on the cassiterite surface. The flotation performance of the combined surfactant was investigated to determine the optimum ratio. Subsequently, the self-assembly behavior of the surfactants in aqueous solutions was examined using surface tension tests and molecular dynamics simulations. Flotation experiments and zeta potential, X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), contact angle, and adsorption capacity analyses were used to explore the flotation behavior and adsorption mechanism at the solid–liquid–gas boundary. The maximum flotation recovery of cassiterite were 45.73 % and 71.25 % when SHA and DBIA were used alone. By contrast, with the developed combined surfactant, the flotation recovery at the same reagent concentration was 84.92 %. The SHA/DBIA surfactant co-adsorbed at the aqueous solution interface, which decreased the surface tension of the solution to 4.943 × 10−4 mol/L and resulted in formation of a stable foam layer. These effects altered the surface properties of cassiterite and enhanced its surface hydrophobicity. Overall, this study provides valuable mechanistic insights into the enhanced chelation complexation of self-assembled surface collectors with metal oxides.

Study on expanding flotation performance differentiation of quartz and magnesite by amino-trimethylphosphonic acid in dodecylamine system

In this paper, amino trimethylene phosphonic acid (ATMP) was introduced into the separation process of magnesite and quartz, in order to reduce the content of associated minerals in magnesite and improve the industrial utilization value of magnesite. Micro-flotation tests showed that under the system of dodecylamine as collector, ATMP can selectively depress magnesite within the alkaline pulp environment. When the dosage of ATMP was 100 mg/L and the pulp pH was 11, the flotation recovery of magnesite was 12.65 % and that of quartz was 91.00 %. Additionally, the findings of the artificial mixed mineral flotation showed that a concentrate with a grade of 43.53 % MgO and a recovery of 91.03 % was achieved. Zeta potential, FTIR and XPS analyses demonstrated that ATMP chelated with the active site Mg2+ on the surface of magnesite through –PO3 group. In addition, DFT calculation indicated that the adsorbed ATMP increased the distance of N atom in dodecylamine (DDA) to the surface of magnesite from 2.671 Å to 5.106 Å. The interaction energy between DDA and magnesite increased from −201.28 kJ/mol to −136.75 kJ/mol, resulting in it difficult for DDA to adsorb on the magnesite surface. However, ATMP was difficult to adsorb on the quartz surface and had no effect on the interaction between DDA and quartz. Therefore, the selective depression effect of ATMP on magnesite was realized.

Novel insights into sylvite flotation modulated by exposing facets

Sylvite (KCl) is a classical soluble mineral with high solubility, endowing the possibility to precisely adjust its surficial structure for flotation recovery. In this work, efforts have been originally made to study flotation behaviors of KCl with (200) and (222) exposing facets. KCl(200) crystals had a higher recovery than that of KCl(222) with octadecylamine hydrochloride (ODA). FTIR and XPS results indicated that interaction force between KCl and ODA was not chemical absorption. Zeta potential results further implied the mechanism that the ODA reacted with KCl by static force and KCl(200) possessed a lower potential than KCl(222) and thus facilitated the flotation process. 2D as well as 3D AFM results provided microscopic details of perfect cubic KCl(200) and octahedron KCl(222) samples where layered growing method of former samples exhibited more edges with hanging Cl bonds, leading to its more negative surficial potential and less hydrophilic property, enhancing flotation recovery. Moreover, adhesion & adsorption force further illustrated that KCl(200) obtained a stronger interaction with bubbles, in coincidence with its better flotation recovery. KCl crystals with (200) exposing faces promoted flotation in comparison with crystal with (222) faces, offering strategy to reserve (200) faces for designing KCl crystals with high recovery.

A novel activation method for regulating surface characteristics and flotation performance of smithsonite: XPS, SEM-EDS, AFM, ToF-SIMS and FT-IR studies

Smithsonite is a typical zinc oxide mineral, and the flotation index is not ideal for the recovery of smithsonite via sulfidization–xanthate flotation. In this study, Pb2+ was used as an activator for the stepwise activation of smithsonite in a sulfidization–xanthate flotation system. Micro-flotation tests and various surface analytical assays were employed to investigate the effects of Pb2+ stepwise activation on the flotation behavior and surface properties of smithsonite. The micro-flotation tests revealed that the flotation recovery of smithsonite reached 90.26 % after the stepwise activation of Pb2+ at an appropriate concentration. X-ray photoelectron spectroscopy, scanning electron microscopy-energy-dispersive X-ray spectroscopy, atomic force microscopy, and time-of-flight secondary ion mass spectrometry indicated that abundant active sites of Pb components appeared on the smithsonite surface after Pb2+ stepwise activation, which promoted the adsorption of S ions on the smithsonite surface. The increase in the proportion of the PbS component after sulfidization effectively enhanced the reaction activity of the mineral surface. Fourier-transform infrared spectroscopy and contact angle measurements showed that xanthate could be stably adsorbed on the smithsonite surface after Pb2+ stepwise activation, thereby enhancing the surface hydrophobicity and flotation behavior of smithsonite. Therefore, Pb2+ stepwise activation can promote sulfidization on the smithsonite surface, improve the reactivity and hydrophobicity of the mineral surface, and substantially increase the flotation index of smithsonite.

Effect of Iron(III) ions on rutile flotation: Surface properties and adsorption mechanism

Various studies have shown that the presence of metal ions in the slurry can significantly impact flotation. However, it was still uncertain how iron, a typical metal ion, affected rutile flotation. Micro-flotation experiments, x-ray photoelectron spectroscopy, icp-oes, solution chemistry calculation, zeta potential and contact angle test were used to explore the effect of iron ions on the surface properties and floatability of rutile in this investigation. Micro-flotation results showed that iron ions not only substantially increased the rutile flotation recovery from 42.27 % to 75.69 % at pH = 4, but also converted the optimal pH of flotation from a point (pH = 4) to a platform (pH = 4–8). Solution chemistry calculations indicated that iron ions could form complexes with hydroxyl to produce FeOH2+, which reacted with benzohydroxamic acid (BHA) to create [Fe(C7H6NO2)2]+ at pH=4–7. The analysis conducted through X-ray photoelectron spectroscopy, coupled with the results obtained from contact angle measurements, revealed that the complex [Fe(C7H6NO2)2]+ had the capability to engage with Ti-OH groups, improving the hydrophobicity of rutile surface. Zeta potential analysis results further illustrated that Fe3+/BHA complexes reinforce the adsorption of BHA and iron ions onto rutile surface by the formation of [Fe(C7H6NO2)2]+. In addition, the O1s peak fitting results and ICP-OES analysis results proved that at the same pH, 60 mg/L was the optimal concentration for iron ion activation, which may be limited by Saturated adsorption capacity of [Fe(C7H6NO2)2]+.

Effect of ultrasonic treatment on the surface roughness and floatability of magnesite and dolomite

This study focuses on the effects of ultrasonic treatment on the surface roughness, flotation behavior, and flotation separation efficiency of magnesite and dolomite in a sodium oleate (NaOL) system. Flotation experiments show that ultrasonic treatment improves the flotation recovery and separation efficiency of these two minerals. We can achieve flotation separation of magnesite and dolomite using 4-mg/L sodium hexametaphosphate. After ultrasonic treatment, magnesite and dolomite achieved flotation recovery of 93.41% and 25.12%, respectively, with a float difference of 68.29%. Atomic force microscopy reveals that ultrasonic treatment increases the surface roughness of both magnesite and dolomite, but the increase is greater for the former. Adsorption capacity tests and contact angle measurements indicate that ultrasonic treatment increases the adsorption capacity of the minerals for NaOL as well as their contact angles in the NaOL system and promotes their flotation. X-ray photoelectron spectroscopy reveals that ultrasonic treatment increases the content of Mg exposed on the magnesite surface and contents of Ca and Mg exposed on the dolomite surface. NaOL is more easily adsorbed on the surface of ultrasonically treated magnesite than on the surface of dolomite. Turbidity analysis reveals that the turbidity of the mixed ore of ultrasonically treated magnesite and fine-grained dolomite is lower than that of the mixed ore of untreated magnesite and fine-grained dolomite; the covering effect of fine-grained dolomite on the surface of ultrasonically treated magnesite is stronger than on the surface of untreated magnesite. Scanning electron microscopy and energy-dispersive X-ray spectroscopy analyses show that fine-grained dolomite undergoes mud covering on the magnesite surface. Ultrasonic treatment not only improves the covering of fine-grained dolomite on the magnesite surface but also affects the form of this covering.

Selective flotation separation of gypsum and quartz using dodecyl amine hydrochloride as collector: Mechanism and application

The selective flotation separation of gypsum and quartz in phosphogypsum (PG) is an urgent problem that is very important for the high‐value utilization of PG. In the work, dodecyl amine hydrochloride (DH) was introduced as a collector for the selective flotation separation of gypsum and quartz. The flotation property and selective mechanism of DH on the surface of gypsum and quartz were researched by single mineral flotation experiments, Fourier transform attenuated total reflection infrared spectroscopy analyzer, zeta potential analyzer, X‐ray photoelectron spectrum, molecular dynamic (MD) simulation, etc. Additionally, H+ was introduced into the mineral‐water system simulated by MD to take into account the effect of acidic conditions on the adsorption of DH. The pre‐adsorption of H+ on the quartz surface under strongly acidic conditions hindered the electrostatic force adsorption of DH on the quartz surface. Furthermore, DH was adopted as a collector in the direct flotation recovery of gypsum from PG, and the gypsum concentrates with productivity of 69.85%, CaSO4·2H2O content of 96.33%, and whiteness of 55.00% were obtained. The SiO2 content in the gypsum concentrate decreased from 9.08% to 0.616%. It suggested that DH could serve as a promising collector in the selective separation of gypsum and quartz in PG via flotation.

Flotation activation mechanism of trithiocyanuric acid to malachite

Malachite is a typical refractory copper oxide mineral. In this paper, trithiocyanuric acid (TMT) was used as a novel activator for the activated flotation of malachite for the first time. The effect of TMT on the flotation behavior of malachite was studied and the activation mechanism was discussed. The flotation test results showed that TMT exhibited superior activation performance over sodium sulfide, achieving a high flotation recovery rate of 97.50 % at TMT 90 mg/L and pH 7. The contact angle confirmed malachite improved from 53.3° to 90.1° after TMT treatment, indicating enhanced hydrophobicity of the mineral surface. FTIR and EDS analyses provided clear evidence of chemical adsorption of TMT tautomers onto the malachite surface. SEM images further illustrated the presence of dense particles formed after TMT treatment. XPS revealed that TMT exhibited a strong adsorption effect on malachite, leading to an increase in copper sites and the formation of highly reactive Cu+. The activation mechanism was elucidated as the reaction between Cu sites on malachite and S and N atoms in TMT, forming Cu-S and Cu–N fractions crucial for activation. The high efficiency and low dosage of TMT make it a promising activator for malachite, offering a novel avenue for the effective recovery of malachite-type copper oxide ore resources.

Quantifying Contributions of Different Repulsion to Film Drainage Time during the Bubble-Solid Surface Attachment and Implications for the Flotation of Fine Particles.

The flotation recovery of fine particles faces serious challenges due to the lack of kinetic energy required for supporting their radial displacement and attachment with bubbles. Generally, the hydrodynamic resistance and repulsive disjoining pressure successively inhibit the liquid outflow intervening between the bubble and solid surfaces. To quantitatively characterize the influence of the main repulsion on film thinning time, experiments have been designed in three different aqueous systems. Bubble surface mobility closely associated with hydrodynamic resistance was determined by the rising bubble technique, and the DLVO theory was employed to confirm the evolution of electrostatic repulsion. The film drainage process was then measured based on the high-speed microscopic interferometry. Furthermore, the influence of the main repulsion on bubble-solid surface interactions was examined by flotation recovery. Results show that the earlier buildup of hydrodynamic force ran through the whole film thinning process, and under immobile conditions, the central region gradually became dominant in film thinning due to the very limited fluid flow at the thinnest rim position. Therefore, to achieve the identical film thickness (∼100 nm), the large hydrodynamic resistance could prolong the film thinning time by about 1 order of magnitude, compared with that induced by electrostatic repulsion, which accounts for the increased flotation recovery by 10% using mobile bubbles. This study not only enhances the understanding of how typical repulsive forces work in film drainage dynamics but also opens up an avenue for enhancing flotation and avoiding wasting resources by modulating bubble surface mobility and thus micro/nanoscale fluid flow.

New Insights into the Role of Thiol Collectors in Malachite Flotation

Malachite is one of the most important copper-bearing oxide minerals; however, it shows poor floatability prior to sulfidization under the thiol collector system. This study investigated the reasons for the low recovery of malachite flotation without sulfidization. The results of adsorption capacity and contact angle test indicated that the malachite surface could adsorb a sufficient amount of the collector, obviously increasing the hydrophobicity of the malachite surface under static conditions. By measuring the amount of inorganic carbon in the flotation solution, it was found that the amount of inorganic carbon in the solution increased significantly when the thiol collectors were added into pulp, which could be attributed to the induced dissolution of the malachite surface by thiol collectors. Solubility tests further demonstrated that the copper ions released from the natural dissolution of malachite proved difficult in regard to reactions with thiol collector to form precipitates; however, the thiol collector induced the dissolution of malachite surface, and so the hydrophobic complexes’ copper-collector could not firmly adsorb on the mineral surface. Fourier transform infrared (FTIR) analysis revealed that thiol collectors do not adsorb stably on malachite surfaces. This was considered to be a substantial reason for the poor performance of malachite flotation without sulfidization.