The adsorption mechanism of Al(III) and Fe(III) ions on bastnaesite surfaces

The adsorption mechanism of Al(III) and Fe(III) ions on bastnaesite surfaces was investigated by a combination of DFT calculation, XPS analysis, adsorption isotherm study and adsorption kinetic investigations. DFT calculation results indicated that ≡CeOH0 and ≡CO3H0 are primary functional groups on bastnaesite surfaces. XPS analysis reveals that Al(III) and Fe(III) ions adsorbed onto the bastnaesite surfaces through the interaction between aluminium/iron hydroxide species and oxygen atoms of surface ≡CeOH0 groups. No interaction between aluminium/iron hydroxide species and ≡CO3H0 groups was detected. Adsorption isotherm studies demonstrated that the adsorption data of Al(III) and Fe(III) ions is fitted relatively well by Freundlich equations, the adsorption kinetic characteristics fitted to pseudo-second order model. Freundlich constants suggested favorable process for Al(III) and Fe(III) ions adsorption, and each adsorbed metal hydroxide specie complex with at least two oxygen atoms of surface ≡CeOH0 groups

Interaction Mechanism between Molybdenite and Kaolinite in Gypsum Solution Using Kerosene as the Flotation Collector

This paper aims to understand the fundamental interaction mechanism between molybdenite and kaolinite in gypsum solution using kerosene as collector. Micro-flotation tests were conducted to study the effect of gypsum solution on the flotation performance of mixed −74 μm molybdenite and −10 μm kaolinite mineral. The results showed that the recovery of molybdenite decreased from 86% to 74% while the gypsum solution concentration increased from 0 to 800 mg/L, indicating the detrimental effect of kaolinite on molybdenite flotation could be enhanced by gypsum solution. This is mainly caused by the slime coating of kaolinite on molybdenite through dissolved calcium ion of gypsum solution. In order to confirm the slime coating phenomenon, zeta potential distribution, scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements were used to investigate interaction characteristics and mechanisms. The zeta potential distribution results revealed that mixed samples had the value between signal molybdenite and kaolinite samples in gypsum solution, which proved the coating phenomenon of kaolinite on molybdenite. Moreover, the coating phenomenon was becoming more and more obvious with the gypsum solution concentration. The coating phenomenon of kaolinite on molybdenite surface was also directly observed from SEM results. The AFM results provided further evidence for the possibility of slime coating, as the adhesion force increased with the gypsum solution concentration, which means the aggregates of molybdenite and kaolinite were becoming more stable

Depression Mechanism of Strontium Ions in Bastnaesite Flotation with Salicylhydroxamic Acid as Collector

Metal ions are widely present in flotation pulp. Metal ions change solution chemistry and mineral surface properties, consequently affecting mineral flotation. In this work, the effect of strontium ions on bastnaesite flotation with salicylhydroxamic acid (SHA) was investigated by microflotation tests, contact angle measurements, zeta-potential measurements, and X-ray photoelectron spectroscopy (XPS) analysis. Microflotation tests confirmed that the addition of strontium ions decreased bastnaesite floatability, compared with that in the absence of strontium ions. Contact angle measurements suggested that the pretreatment of strontium ions decreased SHA adsorption. Zeta potential measurements confirmed that the bastnaesite was depressed by the adsorption of positively charged strontium species, and the lower adsorption capacity of SHA onto the bastnaesite surfaces was obtained after modifying with strontium ions. XPS analysis demonstrated that strontium ions adsorbed onto the bastnaesite surfaces through the interaction between strontium ions and oxygen atoms of surface ≡ CeOH 0 groups. This occurrence hindered surface Ce sites which chelated with SHA and therefore, decreased bastnaesite floatability

Metal Ion Release in Bastnaesite Flotation System and Implications for Flotation

Ca2+, Mg2+, Sr2+ and Fe3+ were found to be commonly released into bastnaesite flotation pulp from minerals with relatively high concentrations. The influence and corresponding mechanism of Ca2+, Mg2+, Sr2+, Fe3+ and Al3+, on bastnaesite flotation, have been studied by micro flotation tests, induction time measurements, adsorption measurements and solution chemistry analysis. It was found that all aforementioned metal ions depressed bastnaesite flotation. The order of depression ability was Fe3+ > Al3+ > Mg2+ > Sr2+ > Ca2+ and the depression ability changed along with pH. The depression was mainly attributed to the adsorption of metals ions, which hindered collector adsorption. The species diagrams of metal ions changed along with pH, consequently changing the adsorption of metal ions on mineral surfaces, and therefore leading to different influences on flotation

Study on the Influence of Metal Ions on the Dispersion of Fine Calcium Gangue Minerals

In this study, the calcium gangue material calcite (−10 μm) was used to investigate the effects of different kinds of metal ions and dosages on the dispersion behavior of calcite. The test results showed that the dispersion behavior of calcite was poor under strongly alkaline conditions without the addition of metal ions, and the reason for that was calcite dissolved ions. The degree of influence of different metal ions on calcite dispersion behavior was Fe3+ > Mg2+ > Na+. The three metal ion dosage tests showed that the dispersion behavior of calcite became poorer with the increase of metal ion dosage. This mainly showed that with the increase of Na+ dosage, the trend of the dispersion behavior of calcite was not obvious, but with the increase of Fe3+ and Mg2+ dosage, the trend of calcite dispersion behavior changed more. The dispersion behavior of calcite was devastated by 5 × 10−4 mol/L Fe3+ at pH = 4–12. The different mechanisms of the three metal ions were identified by zeta potential, solution chemistry, and XPS analysis. Na+ only changed the zeta potential value of the calcite surface, which acted as a compressed electric double layer. However, the formation of metal hydroxide species or metal hydroxide surface precipitation due to the adsorption of Fe3+ and Mg2+ on the mineral surface resulted in the change of the dispersion behavior of calcite

Improving Low Rank Coal Flotation Using a Mixture of Oleic Acid and Dodecane as Collector: A New Perspective on Synergetic Effect

The mixed collector can improve low rank coal flotation efficiency, but its synergistic mechanism needs to be further explored. In this paper, oleic acid-dodecane (OA-D), oleic acid (OA), and dodecane (D) were employed to treat the low rank coal for revealing new synergistic mechanism of the mixed collector. First the surface free energy of the coal, the surface free energy of coal-water and coal-water-coal were calculated. Then wetting heat measurement, X-ray Photoelectron Spectroscopy (XPS) and FTIR were used to analyze synergistic mechanism of the mixed collector in depth. The results showed that OA-D obtained a higher combustible recovery than using OA and D, respectively. The essence of synergetic mechanism of OA-D was that they formed a relatively ordered “supramolecular structure” on the low rank coal surface, especially there were hydrophobic and van der Waals forces between the oleic acid chain and the dodecane chain that can promote the formation of a continuous collector film

Zinc Recovery from Wulagen Sulfide Flotation Plant Tail by Applying Ether Amine Organic Collectors

Separating oxidized zinc minerals from flotation tailings is always a challenge. In this study, a flotation tailing from Wulagen zinc mine in China (Zn grade < 1%) was processed using froth flotation with combinations of amines (OPA 10, OPA 1214, OPA 13, DDA) and Na2S to study the effects of these amines on the zinc recovery as well as their interactions with other reagents, aiming to screen out a proper reagent scheme to improve zinc separation from extremely low-grade zinc flotation tailings. The results show that different amines led to different flotation performance, and the collectors were ranked as OPA 1214, OPA 13, OPA 10 and DDA in a decreasing order based on flotation collectivity and selectivity. An increase in the concentration of each collector increased the zinc recovery but reduced the concentrate zinc grade. Interactions were also observed between different amines and Na2S and Na2SiO3, and OPA 1214 outdid the others in saving the usage of both the Na2S and Na2SiO3. The measured adsorption of collector onto smithsonite was found to correlate well with flotation test results. It was concluded that hydrocarbon chains can be held accountable for the difference in the flotation performance with different amines. The longer the hydrocarbon chain, the stronger the hydrophobic association ability of amine, which is conducive to the selective amine adsorption onto sulfurized smithsonite particles and hence the smithsonite flotation

Tetrahydrofurfuryl-functionalized polystyrene nanoparticles as collectors for low rank coal flotation

In this paper, tetrahydrofurfuryl-functionalized polystyrene nanoparticles (TFPNs) were evaluated as collectors in low-rank coal flotation. A series of TFPNs were prepared by immobilizing tetrahydrofurfuryl groups onto the surface of polystyrene nanoparticles (PNs), and further characterized in terms of their size, shape, surface charge and surface functionalization group concentration (SFGC). The coal flotation performance using TFPNs was compared to that using PNs and diesel oil (DO). The interaction mechanisms between TFPNs and low-rank coal were also discussed. The results show that TFPNs gave higher recovery than that given by PNs and DO. Smaller TFPNs were more effective flotation collectors. The recovery of TFPNs increased firstly and then decreased with SFGC. TFPNs can specifically deposit onto the low-rank coal particles with the hydrogen bonding function between tetrahydrofurfuryl groups and oxygen-containing functional groups, and promote low-rank coal flotation by increasing the hydrophobicity and roughness of coal particle surface with the adsorbed TFPNs. It was demonstrated that TFPNs introduced a new class of collectors for low rank coal flotation

Enhancing low-rank coal flotation using a mixture of dodecane and n-valeraldehyde as a collector

Low-rank coals are difficult to float using common hydrocarbon oily collectors, such as dodecane and diesel. In this investigation, a mixture of dodecane and n-valeraldehyde was used as a collector to enhance low-rank coal flotation. The changes of the contact angle and surface functional groups of low-rank coal were measured before and after different collectors’ adsorption to indicate its absorption mechanism. Surface tension of different collectors was also measured to identify its spreading performance. The results showed that the flotation performance using the mixture as a collector was much better than that using dodecane or n-valeraldehyde solely. When used the mixture of dodecane and n-valeraldehyde as collector, dodecane primarily covers the hydrophobic sites while n-valeraldehyde primarily covered the hydrophilic sites by hydrogen bond promoting adsorption of dodecane at these sites. There existed synergistic effect between dodecane and n-valeraldehyde. Additionally, n-valeraldehyde can reduce the surface tensions to improve the spreading performance of mixed collector on low-rank coal surface. The improvement both in adsorption and spreading was responsible for the enhancement of low-rank coal flotation by using the mixture

Effect of Dodecane-Oleic Acid Collector Mixture on the Evolution of Wetting Film between Air Bubble and Low-Rank Coal

The wetting film evolution process is essential for flotation, especially in bubble–particle attachment. A mixed collector has been proved effective in promoting flotation. In this paper, the effect of a mixed collector (MC) composed by n-dodecane (D) and oleic acid (OA) on wetting film evolution was investigated using the extended Derjagin–Landau–Verwey–Overbeek (EDLVO) theory, the Stefan–Reynolds model, induction time, and zeta potential measurement. The hydrophobic force constant between bubble and coal treated by different collectors was analyzed. The results showed that MC was superior in reducing the induction time and increasing the zeta potential. When bubbles interacted with coal treated by MC, they had relatively low interaction energy, high critical film thickness, and high drainage rate. The order of hydrophobic force constant was no reagent < D < OA < MC. It indicated that the hydrophobic interaction between bubbles and coal particles treated by MC was the strongest because of the synergistic effect of D and OA