Apatite Surface Research Articles

Interaction mechanism of interfacial nano-micro bubbles with collectors and its effects on the fine apatite flotation

This study focuses on the −38 μm apatite as the research subject and investigates the role of interfacial nano-micro bubbles (INMBs) generated by decompression techniques in the collector system of sodium oleate (NaOl) and dodecylamine (DDA). The results reveal that INMBs enhanced the flotation recovery of apatite using the collector NaOl while it had a slight inhibitory effect on apatite flotation with the collector DDA. The impact of INMBs on the apatite flotation was notable in pH 8–9, which could be attributed to the negative surface charge of INMBs. XPS analysis indicates that INMBs did not alter the collector adsorption by which the reagent molecules bonded with the apatite surface. AFM imaging and adsorption capacity experiments further reveal that the INMBs resulted in an adsorption density reduction of the reagent. This drop could be attributed to the nucleation and growth of INMBs, which effectively cleaned the collector molecules from the mineral surface. The transmittance test findings show that INMBs could significantly promote apatite aggregation in the collector system of NaOl rather than DDA. Overall, the difference in the roles of INMBs on apatite flotation using different collectors is considered as the combined influences of negative “surface reagent cleaning” and positive “fine particle aggregation”.

Efficient flotation separation approach of apatite from calcite for phosphate up-grading using phosphorylated starch macromolecules as a selective depressant

Physico-chemical similarities of surface proprieties of calcite and apatite make their separation challenging. Effective flotation separation requires sustainable depressants to mitigate environmental consequences associated with traditional chemical reagents. Here, for the first time we explore the potential of phosphorylated starch (PS) derived from potato waste as a green and effective depressant. Starch was modified using a straightforward phosphorylation process, resulting in PS with a remarkable charge density exceeding 6000 mmol kg−1. The PS was then evaluated for its ability to depress apatite, enhancing the separation efficiency of apatite from calcite in phosphate rock beneficiation via reverse flotation. Micro-flotation experiments revealed PS's distinct depression effect on apatite while minimally impacting calcite. Floatability rates of apatite and calcite were 90.45 % and 92.68 %, respectively. Introducing 10 mg/g PS drastically reduced apatite recovery to <19 %, while calcite recovery remained at 78.80 %. The bench-scale flotation tests demonstrated an upgrading of the phosphate rock to 70,64 % Bone Phosphate of Lime (BPL) with a yield of 89,41 %. Mechanistic studies employing zeta potential (ZP), and wettability analysis elucidated the depression mechanism. Apatite retained hydrophilicity post-PS addition and conditioning with ester, while calcite-acquired hydrophobicity even in the presence of PS. Furthermore, PS exhibited substantial adsorption onto the apatite surface through chemical reactions involving the phosphate groups and the activated calcium sites on the apatite. Overall, PS stands out as a promising, eco-friendly, and remarkably efficient depressant for separating apatite from calcite through flotation.

Application of waste gypsum as novel selective depressant in the flotation separation of apatite from dolomite

The accumulation of gypsum slag not only causes resource wastage, but also poses serious environmental hazards, therefore, utilizing the resources of the main components in gypsum slag is an imperative task. In this study, gypsum was used as an inorganic depressant for the flotation separation of apatite from dolomite through the selective adsorption of gypsum on the surface of dolomite. Micro-flotation experiments showed that sodium oleate exhibited a good ability to collect apatite and dolomite, but poor ability to collect gypsum. At pH 9.5, when 3.75 g/L gypsum was added to the slurry, the recovery of dolomite decreased from 76.77 % to 18.34 %, whereas that of apatite was 86.45 %. Atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy were employed to elucidate the adsorption characteristics of gypsum on the apatite and dolomite surfaces. The results showed that gypsum was selectively adsorbed on the raised particles on the dolomite surface and combined with the active sites of Ca and Mg metal ions. However, the adsorption of gypsum on the surface of apatite was weak and had little effect on the flotation performance. Density functional theory calculations showed that the O in gypsum reacted easily with Ca and Mg metal ions on the mineral surface. The adsorption energies of gypsum at the Ca and Mg sites on the dolomite surface were −81.97 and −86.18 kJ/mol, respectively, whereas the adsorption energy on the apatite surface was only −34.20 kJ/mol. Gypsum is the main component of gypsum slag, and this study provides a potential recycling method for gypsum slag resources.

Reverse cationic flotation of low-grade phosphate ore using quaternary ammonium salt as a collector and its adsorption mechanism

A novel quaternary ammonium salt collector, LH-01, was employed for the reverse cationic flotation of a magnesium-depleted concentrate (P2O5 grade of 19.72wt%, SiO2 content of 44.26wt%). We achieved an outstanding phosphate concentrate with a P2O5 grade of 35.16wt%, a SiO2 content of 6.06wt%, and a P2O5 recovery of 75.88%. This process was accomplished through two sequential reverse cationic flotation processes designed for quartz removal. Importantly, the quartz removal by LH-01 reached 94.17%, far superior to that by dodecyltrimethylammonium chloride, achieving highly selective separation of quartz and apatite. To understand the adsorption mechanism and kinetics of the collector LH-01 on quartz and apatite surfaces, various techniques, such as quartz crystal microbalance with dissipation, atomic force microscopy, and X-ray photoelectron spectroscopy, were employed. Results revealed that the adsorption layer of LH-01 on the apatite surface was thin and rigid, with a significantly lower hydrophobic effect than that of the viscoelastic multiple adsorption layer formed by LH-01 on the quartz surface. This disparity was identified as the primary factor contributing to the selective flotation separation of apatite and quartz. Moreover, the adsorption of LH-01 on the quartz surface was the result of multiple forces, including electrostatic adsorption, multiple-hydrogen-bond adsorption, and intermolecular hydrophobic association.

Flotation collector lauryldiethanolamine: Adsorption configuration impact on collecting efficiency

In the reverse flotation separation of apatite and its associated siliceous gangue minerals, the common collector dodecylamine (DDA) exhibits a poor selectivity. To remedy this issue, this study implements a change to DDA molecular structure by integrating two 2-hydroxyethyl groups at the N atom position, ultimately producing a freshly developed collector, lauryldiethanolamine (LDEA). Micro-flotation experiments reveal that, relative to DDA, LDEA showcases an enhanced selectivity in separating apatite from its associated siliceous gangue minerals quartz and K-feldspar through reverse flotation. This difference primarily stems from the weaker collecting ability of LDEA for apatite particles relative to DDA. Nevertheless, zeta potential measurements and X-ray photoelectron spectroscopic tests consistently show that, under identical dosage conditions, LDEA and DDA exhibit similar adsorption quantities on apatite surfaces. This observation implies that factors beyond its adsorption quantities inevitably influence the collecting ability of LDEA for apatite particles. First-principles calculations unveil markedly different adsorption configurations of LDEA and DDA on apatite surfaces, suggesting that the difference in the adsorption configurations of LDEA and DDA accounts for the significant variance in their collecting abilities for apatite particles.

Innovating an amphoteric collector derived from dodecylamine molecular structure: Facilitating the selective flotation separation of apatite from quartz and dolomite

This paper introduces a novel amphoteric collector, N-dodecyl-β-alanine (DDALA), derived from the molecular structure of dodecylamine, with the incorporation of a propionic acid group. In the study, flotation experiments are undertaken to examine the selectivity of DDALA in apatite flotation. Results demonstrate that DDALA, in combination with xanthan gum (XG) depressant and oleic acid collector successfully accomplishes the reverse flotation separation of apatite from quartz and dolomite. In addition, the synergistic application of zeta potential experiments, X-ray photoelectron spectroscopic tests, and first-principles calculations has been employed to delve into the action mechanisms of DDALA collector and XG depressant. By combining the results with existing research, the paper proposes that the selective adsorption of XG between apatite and quartz surfaces facilitates the selective separation of these two minerals by DDALA collector. Moreover, the intermediate collecting ability of DDALA/oleic acid combined collector for dolomite results from the competitive adsorption of DDALA neutral molecules and oleic acid anions on dolomite surface. Furthermore, the formation of hydrophilic molecular aggregates between DDALA neutral molecules and oleic acid anions on apatite surface diminishes the collecting ability of DDALA/oleic acid combined collector for apatite compared to the individual use of each collector.

Experimental evidence supporting distinct adsorption configurations of N,N-bis(2‑hydroxy-3-chloropropyl) dodecylamine and dodecylamine on apatite surfaces: Quartz crystal microbalance and atomic force microscopy studies

In apatite flotation, a novel amine collector N,N-bis(2‑hydroxy-3-chloropropyl) dodecylamine demonstrates a considerably lower collecting ability than dodecylamine. Nonetheless, studies under identical dosage conditions reveal that the adsorption amounts of N,N-bis(2‑hydroxy-3-chloropropyl) dodecylamine on apatite surface surpass those of dodecylamine. The collecting efficiency of a collector is traditionally linked to its adsorption amount on the surface of a mineral, suggesting that a collector's efficacy increases with its adsorption amount. However, this study indicates that factors beyond adsorption amount significantly impact a collector's efficiency. Through first-principles calculations, it has been discovered that N,N-bis(2‑hydroxy-3-chloropropyl) dodecylamine and dodecylamine possess markedly varied adsorption configurations on apatite surfaces, implying that the variation grant them divergent collecting capabilities in apatite flotation. Supporting these findings, quartz crystal microbalance and atomic force microscopy analyses show the adsorption layer of dodecylamine is nearly triple thickness of N,N-bis(2‑hydroxy-3-chloropropyl) dodecylamine, with a notably different adsorption morphology. These results offer experimental validation of their differing adsorption configurations. This study not only strengthens the theoretical framework for developing selective control technologies of mineral flotation behaviors but also offers more perspectives for designing innovative collector molecules.

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.

A New Perspective on the Biomineralization of Radicular Dentin

The biomineralization of radicular dentin involves complex molecular signaling. The exact mechanism of action remains elusive. However, the literature showed that protein binding sites for calcium ions and mineral precipitation are essential to promote the remineralization process. Dentin organic matrix possesses non-collagenous proteins, such as dentin matrix protein 1 (DMP1), that can initiate and regulate crystal nucleation. Recombinant DMP1 molecules have been thought to perform specific molecular recognition with the apatite surface, guiding calcium phosphate clusters during recruitment through the type I collagen matrix, which serves as a template for controlled biomineralization. The biological basis for the clinical benefits of this process has yet to be completely elucidated. From a clinical perspective, caries, acid erosion, or disinfection protocol treatments can cause dentin demineralization. Given this fact, dentin biomimetic remineralization strategies and treatment strategies aimed at preserving the dentin matrix have been proposed.

The utilization of 1-Dodecyl-3-methylimidazolium bromine ionic liquid in the reverse flotation separation of feldspar from apatite

The utilization of a new collector 1-Dodecyl-3-methylimidazolium bromine (DMB) ionic liquid in the reverse flotation of feldspar from apatite was researched through a series of experiments. The micro-flotation results exhibited that DMB had a good collecting for feldspar while it had little floatability for apatite, and the artificial mixed minerals flotation presented the reverse flotation separation of feldspar from apatite can be realized well by adding the DMB collector. The foam collapse results illustrated that DMB has better foam properties for reverse flotation compared to dodecylamine (DDA). The zeta potential and Fourier Transform Infrared Spectroscopy (FT-IR) measurements indicated that the interaction of DMB with the feldspar surface was much stronger than that of DMB with the apatite surface. The XPS analysis further suggested that the interaction between DMB and apatite surface was weak while that between DMB and feldspar surface was hydrogen-bonding adsorption. As such, this work is expected to provide a meaningful guide for the selection/design of a cationic collector in reverse flotation of feldspar from apatite.

Recovery of Apatite from Magnetic Concentration Tailings by Flotation

Iron concentration tailings contain many valuable minerals, including apatite, which is not currently being recovered despite its use to make fertilizers and chemicals. This article proposes a flotation circuit to recover apatite from tailings generated by mining in Chile, based on laboratory tests and using the “Split Factor” method. The iron tailings were characterized by granulometry, chemical and mineralogical analyses, zeta potential, and contact angle. The effect of the collector, frother, and dispersant dose, along with the number of flotation stages, on both the grade and recovery of P2O5 were studied. The results indicate that it is possible to produce concentrates with a P2O5 grade of 29.1% and 89.6% recovery in a flotation circuit that includes the rougher–scavenger–cleaner stages. To obtain these results, it is only necessary to condition the iron tailings with 400 gt−1 of Atrac-2600, 400 gt−1 of sodium silicate, 10 min of conditioning time, pH adjustment to 10, and a time for the rougher, cleaner, and scavenger stages set at 10, 7.6, and 6.8 min, respectively. A chemical interaction is suggested, where the collector is specifically adsorbed onto the apatite surface.

Novel Fe3O4 Nanoparticles with Bioactive Glass-Naproxen Coating: Synthesis, Characterization, and In Vitro Evaluation of Bioactivity.

Immune response to biomaterials, which is intimately related to their surface properties, can produce chronic inflammation and fibrosis, leading to implant failure. This study investigated the development of magnetic nanoparticles coated with silica and incorporating the anti-inflammatory drug naproxen, aimed at multifunctional biomedical applications. The synthesized nanoparticles were characterized using various techniques that confirmed the presence of magnetite and the formation of a silica-rich bioactive glass (BG) layer. In vitro studies demonstrated that the nanoparticles exhibited bioactive properties, forming an apatite surface layer when immersed in simulated body fluid, and biocompatibility with bone cells, with good viability and alkaline phosphatase activity. Naproxen, either free or encapsulated, reduced nitric oxide production, an inflammatory marker, while the BG coating alone did not show anti-inflammatory effects in this study. Overall, the magnetic nanoparticles coated with BG and naproxen showed promise for biomedical applications, especially anti-inflammatory activity in macrophages and in the bone field, due to their biocompatibility, bioactivity, and osteogenic potential.

Exploration of disodium methylenebis naphthalene sulfonatea as a novel depressant for the flotation separation of apatite from dolomite

To address the flotation separation problem between apatite and dolomite, DMNS (disodium methylenebis naphthalene sulfonate) was selected as a depressant in this research. Micro-flotation results showed NaOl exhibited good floatability for dolomite and apatite, with no significant difference in the floatability between these two minerals. The addition of DMNS completely depressed the floatability of dolomite but slightly affected the floatability of apatite. The artificial minerals mixture flotation ensured that DMNS achieved the separation between apatite and dolomite when the NaOl was used. The adsorption measurement illustrated adsorption amount of DMNS on dolomite surface was more than that of it on apatite surface, the Zeta potential results illustrated NaOl still adsorbed on the apatite surface but did not adsorbed on the dolomite surface after conditioning with DMNS. XPS analysis verified that no effective interaction occurred between DMNS and apatite surface, and DMNS chemically adsorbed on the dolomite surface by the interaction between –SO3H groups of DMNS and Ca2+/Mg2+ of the dolomite surface. First-principles calculations further ensured the higher adsorption energy of DMNS on the dolomite surface. The computational calculation also revealed that the interaction of DMNS with the dolomite surface was much stronger than that with the apatite surface.

The application of a novel amine collector, 1-(dodecylamino)-2-propanol, in the reverse flotation separation of apatite and quartz

This study synthesized a novel amine collector, 1-(dodecylamino)-2-propanol (DDAIP), by incorporating a 2-hydroxy propyl group into the molecular structure of dodecylamine (DDA). Flotation experiments showed that utilizing DDAIP collector resulted in a substantial difference of ∼80% in flotation recoveries between apatite and quartz. Employing DDA as the collector yielded a difference of ∼30% in flotation recoveries between the two minerals. DDAIP demonstrated a superior selectivity in the reverse flotation separation of apatite and quartz in comparison to DDA. Zeta potential experiments indicated that, under identical dosages, DDAIP demonstrated increased adsorption capacities on quartz surface in contrast to DDA, whereas the adsorption amounts on apatite surface remained similar for both the collectors. By combining XPS analysis and first-principles calculations, DDAIP demonstrated enhanced chemical interactions with the Si atoms on quartz surface and a greater number of hydrogen bonds with quartz surface compared to DDA. The presence of an isopropyl group between the hydroxyl and secondary amine groups in DDAIP molecular structure leads to steric hindrance, hindering the simultaneous chemical interactions of the O and N atoms in DDAIP with the Ca2+ ions on apatite surface. Thus, the incorporation of the 2-hydroxy propyl group into DDAIP molecular structure does not enhance its adsorption strength on apatite surface when compared to DDA.

New insights into the influence of mineral surface transformation on the flotation behavior of anhydrite/apatite

Apatite is generally associated with calcium-containing minerals such as anhydrite, which are difficult to separate due to their similar surface characteristics. In this study, the influence of anhydrite on the flotation behavior of apatite in a fatty acid system was systematically investigated using micro-flotation tests, solution chemical calculations, and surface chemical analyses based on the theory of flotation solution chemistry. The single and mixed mineral flotation experiments revealed that an increasing concentration of anhydrite in the mixed ore system rises, apatite flotation is inhibited while anhydrite flotation is activated. The solution chemical calculation results demonstrated that in the mixed system of anhydrite/apatite, the surface dissolution of anhydrite in the pulp will change the solution chemistry environment, resulting in a drastic decrease in the number of surfaces located ions on the apatite surface and inhibiting its flotation. Furthermore, when the pH of the solution exceeds 4.3, the surface of anhydrite transformed to apatite, promoting anhydrite flotation. The results of the X-ray photoelectron spectroscopy (XPS) analysis further confirmed that the phosphate ions dissolved by apatite were adsorbed on the anhydrite surface at pH= 9, forming calcium phosphate films. Based on the above test results, a novel flotation process was designed to realize the selective flotation of apatite from anhydrite-rich phosphate ores. This study can serve as a theoretical foundation and a practical reference for the separation of calcium-containing minerals.

Targeting Longevity Gene SLC13A5: A Novel Approach to Prevent Age-Related Bone Fragility and Osteoporosis.

Reduced expression of the plasma membrane citrate transporter SLC13A5, also known as INDY, has been linked to increased longevity and mitigated age-related cardiovascular and metabolic diseases. Citrate, a vital component of the tricarboxylic acid cycle, constitutes 1-5% of bone weight, binding to mineral apatite surfaces. Our previous research highlighted osteoblasts' specialized metabolic pathway facilitated by SLC13A5 regulating citrate uptake, production, and deposition within bones. Disrupting this pathway impairs bone mineralization in young mice. New Mendelian randomization analysis using UK Biobank data indicated that SNPs linked to reduced SLC13A5 function lowered osteoporosis risk. Comparative studies of young (10 weeks) and middle-aged (52 weeks) osteocalcin-cre-driven osteoblast-specific Slc13a5 knockout mice (Slc13a5cKO) showed a sexual dimorphism: while middle-aged females exhibited improved elasticity, middle-aged males demonstrated enhanced bone strength due to reduced SLC13A5 function. These findings suggest reduced SLC13A5 function could attenuate age-related bone fragility, advocating for SLC13A5 inhibition as a potential osteoporosis treatment.

Interaction and Inhibition Mechanism of Sulfuric Acid with Fluorapatite (001) Surface and Dolomite (104) Surface: Flotation Experiments and Molecular Dynamics Simulations

The natural wettability of apatite and dolomite and the effect of sulfuric acid (H2SO4) and sodium oleate (NaOl) on the floatability and wettability of both minerals were studied using single-mineral flotation and contact angle measurement. The flotation experiments demonstrated that adding NaOl, apatite, and dolomite had good floatability. After adding H2SO4, the floatability of apatite decreased significantly. H2SO4 effectively inhibits apatite flotation. Contact angle measurements show that the use of H2SO4 induces a significant difference in surface wettability between apatite and dolomite. The moderate addition of H2SO4 can increase the contact angle of dolomite. In order to study the selective inhibition mechanism of H2SO4 in phosphorite flotation, molecular dynamics simulations (MDSs) were conducted to investigate the interaction between H2SO4 and fluorapatite and dolomite at the atomic–molecular level. The results of MDSs reveal that H2SO4 interacts with Ca sites on both fluorapatite and defective dolomite surfaces, hindering the interaction of NaOl with Ca sites on both mineral surfaces. SO42− ions cannot prevent the interaction of oleate ions with Mg sites on dolomite surface. It is worth mentioning that SO42− ions occupy the defective vacancies formed due to the dissolution of CO32− on the surface of dolomite and interact with Ca sites. The remaining H2SO4 is subsequently adsorbed onto the surface of dolomite. Experimental and simulation results show that, due to the interaction of H2SO4 and NaOl, the surface of apatite can still undergo hydration forming a water molecule layer and maintaining a macroscopic hydrophilic property. In contrast, the oleate ions form an adsorption layer on dolomite transitioning it from a hydrophilic to a hydrophobic state. During the phosphate flotation process, the addition of an appropriate amount of sulfuric acid can further diminish the hydration of the dolomite surface, so that the surface of dolomite is more hydrophobic.

The interaction mechanism of a novel polymer depressant with apatite and dolomite surface and its implication on flotation: Experimental tests and DFT calculation

The efficient removal of dolomite from phosphate ores is vital for the subsequent production of phosphate fertilizer. This work investigated the interaction mechanism of poly(sodium styrene sulfonate) (PSS) on apatite and dolomite surface and its implication on flotation through Micro-flotation, adsorption capacity, Zeta potential, SEM-EDS and density functional theory simulation. Flotation results proved that PSS was able to depress dolomite efficiently in broad pH range (8–12). Contact angle, Zeta potential, adsorption capacity and SEM-EDS measurement confirmed that PSS was more prone to adsorb on dolomite rather than that on apatite, which hindered sodium oleate (NaOL) to adsorb on dolomite but almost didn’t influence NaOL to interact with apatite surface. DFT calculations confirmed that the 2p orbital of oxygen atoms within sulfonate groups hybridized with 4s orbital of calcium and 3s orbital of magnesium atoms on dolomite surface to form OCa, OCa and OMg covalent bond, while PSS weakly physisorbed on apatite via electrical interaction, due to the significant difference in steric hindrance and active atom density. PSS exhibited good selectivity and environmental compatibility as dolomite depressant in the beneficiation of phosphate ores for sustainable production of phosphate fertilizer.

Flotation Behavior and Interface Characteristics of Apatite with Co-Depression by Sulfuric Acid and Phosphoric Acid

Phosphate ore is an important strategic mineral resource. The efficient utilization of phosphate resources faces challenges such as low grade of raw ore and difficulty in discharging gangue minerals. One of the key problems to be solved urgently in the reverse flotation of phosphate ore is the effective depression of apatite. However, research on the influence mechanism of acid depressants on the surface properties and adsorption characteristics of apatite is still insufficient. In this study, the influence of different depressants (such as sulfuric acid, phosphoric acid or mixed acid of sulfur acid and phosphorus acid) on the flotation separation performance of an artificial mixture of apatite and dolomite (gangue mineral) was investigated through laboratory flotation tests. On this basis, with the addition of different depressants, the contact angle, zeta potential, XPS and TOC were used to investigate the surface wettability, surface charge, surface species and the adsorption characteristics of the collector (sodium oleate) on the apatite surface, and, accordingly, the inhibiting mechanism was discussed. The results show that, when mixed acid of sulfur acid and phosphorus acid is used as a depressant, a concentrate with a P2O5 grade of 33.53% and a recovery of 88.92% can be obtained, and the parameters are better than when using phosphoric acid with a P2O5 grade of 30.15% and a recovery of 80.12% or sulfuric acid with a P2O5 grade of 30.12% and a recovery of 80.58%. Our analysis shows that the mixed acid has the best inhibiting effect on apatite, which is mainly due to the following: (a) after adding the mixed acid, chemicals such as CaSO4, CaHPO4/Ca(H2PO4)2 are generated on the surface of apatite, resulting in a significant reduction in the contact angle and stronger surface hydrophilicity; (b) the mixed acid reduces the zeta potential of apatite, produces new species and weakens the non-selective adsorption of negatively charged oleate on the surface of apatite, thus preventing the apatite from floating.

Selective depression by using environment-friendly depressant pectin in apatite and dolomite flotation system

The difficulty of apatite and dolomite to be efficiently separated by froth flotation due to similar physical and chemical properties of both minerals in using fatty acid collectors without any depressants. In this study, pectin was explored as an efficient and environment-friendly depressant in flotation to separate apatite and dolomite. In the micro-flotation experiments, pectin displayed an intense depressing effect in dolomite flotation and slightly affected apatite flotation. Quantum chemical calculation was used to predicated the reactive site of pectin, the results demonstrated that oxygen atoms of COO, OH and COC in pectin display the most negative regions. The Zeta potential results indicated pectin was adsorbed on the dolomite surface selectively and depressed the adsorption of sodium oleate on the dolomite surface due to electrostatic repulsion effect. The Fourier transform infrared (FTIR) spectrum measurements uncovered that the selective separation of pectin was due to OH of pectin molecules. The Raman spectrum demonstrated that weak adsorption of pectin on the apatite surface was due to CO of pectin molecule, while the strong adsorption is regard as COO and COC of pectin for dolomite. XPS results indicated that COO of pectin can chelate with Ca2+ and Mg2+ of dolomite surface and depress dolomite flotation. Hence, pectin was be utilised as an eco-friendly and highly selective depressant.