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In order to enhance the reverse flotation effect of hematite, dodecyl trimethyl ammonium chloride (DTAC) and a mixed anionic/cationic collector of DTAC and tall oil were selected for flotation studies on quartz and hematite. Surface tension tests, FT-IR, XPS analysis, and molecular dynamics (MD) simulations were also conducted in order to investigate the interaction mechanism of the mixed collector on the quartz surface. The results revealed that, at a natural pH (approximately 7.0) and 298 K, and with a dosage of 20 mg/L for the mixed collector (mDTAC:mtall oil = 3:1) and 4 mg/L for causticized starch, the recovery rates of quartz and hematite were 94.67% and 8.69%, respectively. Compared to the use of a single DTAC, the mixed DTAC/tail oil collector enhanced the flotation effect under constant variables. Additionally, a comparison of temperature and surface tension for monomineral flotation and artificially mixed ore flotation tests showed that the mixed collector was less influenced by temperature, compared to the single DTAC, and exhibited good resistance and more effective separation of quartz and hematite at lower temperatures. The analysis of FT-IR, XPS, and MD simulations revealed that the single DTAC collector primarily adsorbed onto quartz through physical adsorption and hydrogen bonding, while the combination of tall oil and DTAC enhanced the adsorption of the collector on the quartz surface. [ABSTRACT FROM AUTHOR]

Water quality, particularly hardness, plays an important role in affecting the floatability of minerals as it interferes with the chemical/electro-chemical characteristics of mineral surfaces and their interactions with flotation reagents. It could become unpredictable when water sources characterized by different calcium or magnesium ion distributions were involved. This study aimed to identify the role of Ca2+/Mg2+ ions in the recycled water on the cationic reverse flotation selectivity of iron oxides through a series of bench/micro flotation tests, zeta potential, powder contact angle, and Fourier Transform Infrared (FTIR), etc. The results pointed out that the use of recycled tailing water deteriorates the flotation selectivity and dilutes the concentrates. This can be largely attributed to the presence of Ca2+ ions at higher concentrations as they induce a drop in the Fe recovery and an increase in SiO2 content while an increase in the content of Mg2+ ions seems to have little effect on the quality of concentrate. As evidenced by the data from micro-flotation, powder contact angle, zeta potentials, and FTIR, a hydrophilic colloidal layer formed by Ca-based hydrolyzed compounds, such as Ca(OH)+ or, CaCO3(s), etc., on quartz could change its zeta potentials and disturb its interactions with a cationic collector. They also play a role in weakening the flocculation of starch on hematite probably by prelocking the acidic groups on the starch remnants and contracting their configurations, thus preventing their adsorption on mineral surfaces. However, magnesium ions seem to be beneficial to in strengthening the flocculation of starch on hematite as magnesium-based species could act as adsorption bridges of between starch and mineral surfaces. [ABSTRACT FROM AUTHOR]

In order to enhance the reverse flotation effect of hematite, dodecyl trimethyl ammonium chloride (DTAC) and a mixed anionic/cationic collector of DTAC and tall oil were selected for flotation studies on quartz and hematite. Surface tension tests, FT-IR, XPS analysis, and molecular dynamics (MD) simulations were also conducted in order to investigate the interaction mechanism of the mixed collector on the quartz surface. The results revealed that, at a natural pH (approximately 7.0) and 298 K, and with a dosage of 20 mg/L for the mixed collector (mDTAC:mtall oil = 3:1) and 4 mg/L for causticized starch, the recovery rates of quartz and hematite were 94.67% and 8.69%, respectively. Compared to the use of a single DTAC, the mixed DTAC/tail oil collector enhanced the flotation effect under constant variables. Additionally, a comparison of temperature and surface tension for monomineral flotation and artificially mixed ore flotation tests showed that the mixed collector was less influenced by temperature, compared to the single DTAC, and exhibited good resistance and more effective separation of quartz and hematite at lower temperatures. The analysis of FT-IR, XPS, and MD simulations revealed that the single DTAC collector primarily adsorbed onto quartz through physical adsorption and hydrogen bonding, while the combination of tall oil and DTAC enhanced the adsorption of the collector on the quartz surface.

In view of the difficulty and low efficiency of fine hematite flotation, nanobubbles with special interfacial properties were applied to reverse the flotation of hematite to improve the flotation behavior and separation performance of fine particles. The Box-Behnken response surface method was used to design the experiments and optimize the reagent dosage for reverse nanobubble flotation of hematite from the flotation feed at Anqian Mineral Processing Plant by specifically analyzing the effect of each factor and the interactions between factors on the flotation performance. The results show that collector TD-Ⅱ and corn starch had more significant impacts on grade and recovery than lime and the interactions between starch, lime, and collector TD-Ⅱ had significant effects on iron grade. The iron recovery is 82.27 % and the iron grade is 67.32 % for the concentrate when 3.0 kg/t corn starch, 1.5 kg/t lime, and 0.78 kg/t collector TD-Ⅱ are added. The kinetic flotation experiments confirm that the introduction of nanobubbles in flotation can improve flotation kinetics and concentrate recovery. The application of the nanobubble flotation process will help resolve the difficulty in the efficient flotation of fine particles, which is of great significance to improving the technical performance indicators and economic benefits of the mineral processing plant. [ABSTRACT FROM AUTHOR]

Mineral flotation test， combined with laser particle size test， scanning electron microscope (SEM)， mineral surface potential and XPS (X-ray photoelectron spectroscopy) were used to study the behavior and mechanism of polyoxyethylene oxide (PEO) flocculation of fine kaolinite in the process of hematite reverse flotation. The flotation test showed that the addition of PEO improves the mineral recovery of kaolinite and the separation efficiency of artificial mixed ore， which is conducive to promoting the reverse flotation separation of hematite and kaolinite. The results of laser particle size test and SEM showed that PEO does not flocculate hematite， but flocculates kaolinite particles to increase their apparent particle size. Zeta-potential tests and XPS analysis indicated that chemical adsorption of PEO occurs on the surface of kaolinite particles， and its Zeta-potential is positively shifted. Therefore， PEO has certain guiding significance in the study of reverse flotation separation of hematite and kaolinite. [ABSTRACT FROM AUTHOR]

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Chlorite is often associated with hematite and tends to form microfine particles during grinding, making it challenging to recover and separate from hematite through flotation. This study innovatively applies an ester-based cationic polyacrylamide (CPAM) as a flocculant in a reverse flotation system using dodecylamine (DDA) as a collector, to flocculate and recover microfine-grained chlorite. The method achieves efficient separation between microfine chlorite and hematite. Laser particle size testing and optical microscopy show that CPAM significantly increases the apparent particle size of microfine chlorite, causing it to aggregate into flocs, while having a extremely weak effect on hematite flocculation. Further analysis using techniques like Zeta potential, contact angle measurement, Fourier-transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) reveals CPAM's stronger adsorption affinity for chlorite compared to hematite. The ester groups in CPAM selectively form hydrogen bonds with chlorite's surface H atoms, enhancing its hydrophobicity. Particle-bubble attachment angle testing confirms that the flocculated chlorite flocs exhibit better floatability and higher efficiency in collision and adhesion with bubbles. Thus, CPAM serves as an efficient flocculant for reverse flotation separation of microfine chlorite and hematite. [Display omitted] • Flocculation reverse flotation of microfine-grained chlorite and hematite. • Application of CPAM containing ester groups as a novel hydrophobic flocculant. • Selective flocculation of microfine-grained chlorite. • Analyzed the adsorption mechanism of CPAM on the surface of hematite and chlorite. • Visualized the analysis of the wrapping angle between chlorite and bubbles. [ABSTRACT FROM AUTHOR]

The greater demand for high-quality iron ores has forced the iron and steel industries to utilize low-grade iron ores, such as banded hematite quartzite (BHQ). In the present work, a striped hematite quartzite sample from the Haraginadoni area, in the Sandur schist belt, Ballari District, Karnataka, India, was subjected to characterization studies and conventional mineral processing methods to produce pellet-grade concentrate, assayed as Fe > 63.0%, SiO2 + Al2O3 < 7%, (Al2O3/SiO2 < 0.5). The sample was analyzed as 35.70% Fe, 47.44% SiO2, 0.75% Al2O3, 0.06% Mn, 0.07% TiO2, 0.03% P, 0.02% S, and 0.83% LOI. We focused on two routes of beneficiating BHQ samples: (1) conventional gravity followed by reverse floatation and (2) magnetic separation followed by cleaning of magnetic concentrate by reverse floatation. Route 1, achieved pellet-grade concentrate through assaying, and was 63.73% Fe, 6.20% SiO2, 0.19% Al2O3, 0.03% Al2O3/SiO2, and 0.23% LOI, D80 45 µm, with 70.1% Fe recovery and 62.8% concentration efficiency at 39.6 wt% yield. Using Route 2, the process consisted of WHIMS at −74 µm, D80 54 µm, 10,000 Gauss, and with a 3 mm ball matrix, followed by flotation of the WHIMS concentrate, which produced a concentrate through assaying and was 63.34% Fe, 6.30% SiO2, 0.20% Al2O3 (0.03 Al2O3/SiO2), and 0.20% LOI with 77.4% Fe recovery, achieving a 68.8% concentration efficiency at 44.0 wt% yield, meeting pellet-grade specifications. Comparing and analyzing both routes for the concentration methods, Route 2, i.e., WHIMS and the reverse flotation of WHIMS concentrate, was amenable compared to Route 1. [ABSTRACT FROM AUTHOR]

An iron ore has the characteristics of many kinds of minerals and high content of both aluminum and silicon. The contents of TFe, MFe, SiO2 and Al2 O3 are 24.94%, 3.99%, 33.81% and 13.75% respectively. The results of chemical phase analysis of iron show that the percentage of iron in magnetite is 16.00%, in hematite is 36.49%, and in ferric silicate is 41.34%. In order to make full use of the ore resources, the technological flowsheet of low intensity magnetic separation - high intensity magnetic separation - reverse flotation and new collector BK448 were used in the beneficiation test, and the final indexes were obtained as follows: the iron grade of iron concentrate 1 was 65.45% and the iron recovery was 15.43%, the iron grade of iron concentrate 2 was 60.86% and the iron recovery was 31.42%. In a word, the iron ore in the magnetite and hematite in the total iron share of 42.49%, the total iron recovery of 46.85% of the better indexes. [ABSTRACT FROM AUTHOR]

Depressant carboxymethyl chitosan (CMCS) was introduced to reverse flotation of quartz from hematite using collector DDA. Microflotation experiments presented that CMCS completely depressed the hematite flotation while it had little effect on quartz flotation. The mineral mixture flotation confirmed the reagent scheme of DDA/CMCS could achieve efficient separation of quartz from hematite. It was also found that CMCS has better selective depression ability than the widely-used starch. Zeta potential measurements illustrated that CMCS could prevent DDA adsorption onto the hematite surface, while it did not affect the interaction between DDA and quartz surface. X-ray photoelectron spectroscopy (XPS) indicated that CMCS interacted with the Fe(III) components of hematite by chemisorption, which was stronger than the bonding between starch and hematite. Molecular dynamics simulation (MDS) further revealed the twice interaction energy of CMCS with (001) hematite surface than that of starch. Hence, CMCS has the potential to replace starch in practice. [Display omitted] • CMCS was firstly utilized as a depressant for the reverse flotation of quartz from hematite. • CMCS presented better performance than widely-used depressant starch. • CMCS was hardly adsorb onto the quartz surface. • CMCS interacted with Fe(III) species at the hematite surface by chemical adsorption. • CMCS has twice interaction energy with (001) hematite surface than starch. [ABSTRACT FROM AUTHOR]

Sodium carboxymethyl cellulose (CMC) is a potential depressant which is an indispensable reagent for the treatment of complex refractory iron ores during reverse flotation. In this study, the interaction force between hematite particles adsorbed with CMC and bubbles was calculated, thereby revealing the inhibitory mechanism of CMC on hematite particles. When dodecylamine (DDA) was 15 mg/L and CMC was 3 mg/L, pH=10, the content and recovery rate of hematite reached 83.25% and 87.41%, respectively. Zeta potential tests showed that adsorption of CMC hindered the adsorption of DDA on hematite. AFM images visualized the adsorption status and adsorption layer thickness of CMC on the surfaces of hematite and quartz. FTIR results indicated that the adsorption of CMC on the surface of hematite was strong chemical adsorption, but the adsorption on quartz was physical adsorption. Based on the extended DLVO theory, the total potential of interaction between hematite particles adsorbed with CMC and bubbles was measured. The calculation results demonstrated that the hydration repulsion interaction potential owing to the adsorption of CMC dominated the total potential energy, preventing the adhesion of hematite and bubbles. [Display omitted] [ABSTRACT FROM AUTHOR]

Hematite is commonly upgraded in China using a reverse anionic flotation process with starch as depressant for hematite, Ca2+ as activator and fatty acids as collector for quartz. The Anshan type of hematite is well known for its low grade, fine dissemination, difficulty in upgrading, and huge reserve in China. To investigate effects of nanobubbles and different reagents on the flotation process of this particular hematite, batch flotation tests were conducted with a mechanical flotation cell integrated with a cavitation device that generates nanobubbles under different process parameters including corn starch dosage, lime (CaO) dosage, collector dosage, and air flow rate through the nanobubble generator. Significant improvements in hematite flotation performance was achieved in the presence of nanobubble. The nanobubble flotation results and associated mechanisms are discussed based on up-to-date chemistry of hematite flotation and unique nanobubble characteristics. Unlabelled Image • A mechanical nanobubble flotation system was developed for reverse hematite flotation. • Nanobubbles were able to enhance reverse anionic flotation of hematite. • Different flotation reagents were investigated for their impacts on reverse nanobubble flotation. • Nanobubble flotation produced a concentrate of 68% grade and 84% recovery. • Nanobubble enhanced flotation mechanisms are presented. [ABSTRACT FROM AUTHOR]

• Addition of starches decreased the R f and R c of quartz or hematite particles. • At each experimental condition tested, R f was much higher than R c. • The decreases in R f and R c coincided with the increase in the aggregate size. • The R f and R c of Fe in the flotation of quartz-hematite mixture were measured. This paper reports the measured froth zone (R f) and collection zone (R c) recoveries in the flotation of pure quartz, pure hematite, and a quartz-hematite mixture with one of three corn starches with different mass ratios of amylose to amylopectin: waxy starch (0:100), normal starch (27:73), and Gelose 50 (50:50). The flotation tests were carried out at continuous mode using a three-product column at different pHs and starch concentrations with sodium oleate as collector and calcium chloride as activator. It was found that both R f and R c were significantly affected by pH and starch type and concentration. In the flotation of pure quartz or hematite, addition of each of the corn starches tested would decrease the R f and R c , with the effects following the order of waxy starch > normal starch > Gelose 50. The decreases in R f and R c coincided with the increase in the aggregate size caused by addition of these starches. Possible correlations between R f , solid flux at the pulp-froth interface and R c were examined. In the flotation of the quartz-hematite mixture, the changes in R f and R c of Fe caused by varying starch type and dosage were consistent with those in the flotation of pure hematite. [ABSTRACT FROM AUTHOR]

Abstract The depression of hematite in the reverse flotation system of oleate-starch-hematite was investigated at the atomic level by atomic force microscopy (AFM) combined with density functional theory (DFT). AFM imaging and cross-sectional imaging show that the adsorption configurations of oleate and starch on hematite were in shuttle and flake patterns, respectively, resulting in a greater adsorption thickness and adsorption area for starch than for oleate on the hematite surface. After functioned by starch, hematite was almost fully covered by starch so that there was no sufficient space for the adsorption of oleate. Corn starch was also detected aggregating fine hematite particles just like a flocculant. In the DFT study of the system, convergence tests were conducted to get the optimized hematite crystal geometry. The calculated interaction energies and Mulliken populations verified the favorable adsorption of oleate and starch on the hematite surface. Results indicated that covalent bonds formed between oleate and hematite, as well as between starch and hematite. However, in the oleate-starch-hematite system, the calculations showed that the distance between oleate and hematite in the presence of starch was too long to allow the adsorption of oleate. As for the water effect on the depression of hematite, the water molecules acted as a bridge between starch and the hematite surface by hydrogen bonds and were accompanied by chemical bonds between hematite surfaces and starch, which led to the depression of hematite. Therefore, in reverse flotation, oleate is hindered from adsorbing on the starch-covered hematite surface. The work presented here has profound implications for future studies of the depression of hematite, and may help solve the problem of screening and design of depressant of hematite. Highlights • AFM inspected the adsorption morphologies of starch and oleate on hematite. • DFT investigated the binding information of oleate and starch on hematite surface. • DFT calculations supported AFM experimental investigations. • Results revealed starch hindered the adsorption of oleate on hematite surface. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel low-foam viscous cationic collector DTDAB was synthesized. • DTDAB exhibited superior collector ability and selectivity than DTAB. • Insertion of hydroxyl could reduce interface tension and foam coalescence of collector. • Better selectivity was achieved by regulating the size of the polar group. Traditional cationic collectors generally exist some disadvantages, such as high foam viscosity and difficulty in defoaming, which worsening the flotation separation effect. Herein, a novel cationic collector-dodecyl trihydroxyethyl ammonium bromide (DTDAB) with low-foam viscous was synthesized to optimize the reverse flotation system of hematite ore, which was achieved by introducing three hydroxyethyl groups into the nitrogen atoms of dodecyl trimethyl ammonium bromide (DTAB). The analysis of foam collapse performance indicated that the introduction of hydroxyl groups into hydrophilic head groups of DTAB reduced the interface surface tension and bubble coalescence, which were consistent with the design expectations. Meanwhile, flotation behaviors were systematically studied, and the results showed that the concentrates with 63.89 % total iron (TFe) grade and 89.27 % total iron recovery was obtained at pH 6.81, when the concentration of DTDAB and starch was 20 mg/L and 5 mg/L, respectively. Besides, the possible flotation mechanism was further studied by means of contact angle, Atomic force microscope (AFM), Fourier transforming infrared spectra (FT-IR), X ray photoelectron spectroscopy (XPS), and Density functional theory (DFT) calculation. The results comfirmed that the adsorption between DTDAB and quartz was caused by electrostatic force and hydrogen bonding affinity. In conclusion, it can be confirmed that the novel cationic collector DTDAB with low-foam viscous has the potential for the hematite reverse flotation desilication. [ABSTRACT FROM AUTHOR]

Given the gradual increase in the chlorite content of hematite ores, pulp properties seriously deteriorate during flotation. The traditional anion reverse flotation of hematite cannot effectively eliminate the effects of chlorite, leading to a significant decrease in the total Fe (TFe) grade of the concentrate. In this work, the effect of sodium alginate on the reverse flotation of hematite was systematically investigated. Flotation tests of artificially mixed ores were conducted, and the results showed that sodium alginate can significantly improve the removal rates of quartz and chlorite. The adsorption measurements, infrared spectroscopy, and contact angle tests demonstrated that sodium alginate adsorbs on the quartz surface by chelating with calcium ions, thereby weakening the steric hindrance of oleate ions and increasing the adsorption capacity of sodium oleate to ultimately improve the removal rate of quartz. Furthermore, owing to its lower density and fine particle size, chlorite is easily entrained into the foam layer. Sodium alginate dramatically increases the liquid-to-gas ratio of the foam layer by increasing pulp viscosity, thereby increasing the entrainment rate of chlorite and finally improving its removal rate. The core content of this thesis bears significance in improving the Fe grade in the reverse flotation of chlorite-containing hematite. [ABSTRACT FROM AUTHOR]

The adhesion behavior between particles in the pulp will seriously affect the index of concentrate. In this paper, the effect of citric acid on chlorite in hematite reverse flotation system was studied. The flotation test and settlement test of artificial mixed ore showed that a lower dosage of citric acid could significantly improve the removal rate of chlorite. The mineral contact angle measurement and zeta potential analysis, combined with the extended DLVO theory showed that chlorite is easily adsorbed on the surface of hematite, results in a lower removal rate, and the phenomenon was analyzed by a laser particle size analyzer and optical microscope. The results showed that citric acid can reduce the apparent grain size of artificial mixed ore and improve the dispersion degree of pulp by changing the wettability and surface potential of the minerals, thus increased the removal rate of chlorite. [ABSTRACT FROM AUTHOR]

In this paper, a novel macromolecular depressant of hematite, polymaleic anhydride-triethylenetetramine (PMTA) with multiple carboxyl and amine groups, has been synthesized and used for cationic reverse flotation separation of quartz from hematite. The structure is characterized by Fourier transform infrared spectroscopy (FT-IR). The depression performance and adsorption mechanism of PMTA onto hematite and quartz surface are investigated by micro-flotation tests, FT-IR, zeta potential and X-ray photoelectron spectra (XPS). The micro-flotation results indicate that PMTA exhibits a good depression performance compared to starch. We find that 98.29% of hematite is depressed with a grade of 65.24% at pH 11 with 12 mg/L dosage. The FT-IR spectra, zeta potential and XPS analysis demonstrate that PMTA may mainly chemisorb on the hematite surface by Fe O bonds, and mainly adsorb on the quartz surface by hydrogen bond interaction. PMTA could be a good depressant of hematite in the separation from quartz. [ABSTRACT FROM AUTHOR]

Reverse flotation desilication with anionic collector sodium oleate (OL) and activator Ca2+ is a common beneficiation method to purify hematite. Herein, the separation mechanism of hematite and quartz were systematically investigated by experiments and DFT calculations with the effect of surface hydroxylation fully considered. Flotation results showed that the success of anionic reverse flotation of hematite was inseparable from the activation of quartz by Ca2+. In addition, the use of sodium humate (HM), which selectively inhibited hematite, was also very critical. The Zeta potential revealed that the activator Ca2+ ions were highly selective for quartz and depression HM was highly selective for hematite. SEM clearly showed that Ca species were adsorbed on the quartz surface, which was confirmed as chemisorption by XPS. DFT calculations further confirmed that the adsorption of HM on the surface of hematite was more favorable than that of quartz, while Ca2+ on the surface of quartz was more favorable than that of hematite, and the chemisorbed Ca2+ ions on the quartz surface provided targeted reaction sites for the subsequent adsorption of OL, which enabled the activated quartz to overflow into the froth products, while the inhibited hematite to sink and concentrate in the flotation cell. [Display omitted] • Collector OL is less competitive than hydroxyl on the mineral surfaces. • Better selectivity of Ca(II) to the hydroxylated quartz than that of hematite. • Better selectivity of HM to the hydroxylated hematite than that of quartz. • OL can be effectively adsorbed on hydroxylated quartz in the presence of Ca(II). [ABSTRACT FROM AUTHOR]

An iron ore mineral processing plant in Brazil treating Itabirite ore was assessed by sampling a circuit consisting of Wemco 144 mechanical cells, as part of the AMIRA P9P collaborative research project. This paper presents and discusses the results of entrainability, water recovery and quartz and hematite grades associated to hydrodynamic parameters. The results indicated strong correlation between water recovery and hematite losses which was intensified by the operating conditions of the circuit. A potential alternative to reduce the hematite losses through entrainment and to increase quartz removal was to modify the traditional circuit design to treat rougher and cleaner/recleaner tails in different stages. In addition, the scavenger residence time must be matched to the quartz floatability. Changes to design and operation of these circuits are needed to sustain concentrate recovery and grade as iron ores become finer. [ABSTRACT FROM AUTHOR]

The effects of siderite on reverse flotation of hematite were investigated using micro flotation, adsorption tests, and Fourier transform infrared spectroscopy. The flotation results show that interactions between siderite and quartz are the main reasons that siderite significantly influences the floatability. The interactions are attributed to dissolved siderite species and fine siderite particles. The interaction due to the dissolved species is, however, dominant. Derjaguin-Landau-Verwey-Overbeek (DLVO) theoretical calculations reveal that adhesion on quartz increases when the siderite particle size decreases and that fine particles partly influence quartz floatability. Chemical solution calculations indicate that the dissolved species of siderite might convert the surface of active quartz to CaCO precipitates that can be depressed by starch. The theoretical calculations are in good agreement with the results of adsorption tests and FTIR spectroscopy and explain the reasons why siderite significantly influences reverse flotation of hematite. [ABSTRACT FROM AUTHOR]

[Display omitted] • NaHA selectively inhibited hematite and realized the effective separation of quartz and hematite. • NaHA obviously changed the zeta potential of hematite and prevented the further adsorption of DDA. • The adsorption capacity of NaHA on hematite surface was much greater than that on quartz surface. • There was chemical adsorption of NaHA on the surface of hematite but no on the quartz. • NaHA adsorbed on the surface of hematite through coordination with surface iron. The inhibitor can improve the hydrophilicity of minerals and prevent minerals from interacting with collectors. It plays an important role in the reverse cation flotation of iron ore, and it has become the focus of current research to find efficient, environmental friendly and cheap inhibitors. Sodium humate (NaHA) is a product extracted from weathered Lignite by means of biodegradation and organic decomposition. In this study, this new inhibitor NaHA was used to separate hematite and quartz. The results of micro-flotation showed that an appropriate concentration of NaHA could selectively inhibit hematite and realize the effective separation of quartz and hematite. Zeta potential and adsorption measurement results showed that after treatment by NaHA, the negative shift of zeta potential of hematite was more obvious, and could prevent the further adsorption of dodecylamine (DDA). The adsorption capacity of NaHA on hematite surface was much greater than that on quartz surface. FTIR results showed that there was chemisorption of NaHA on the surface of hematite but no on the quartz. XPS analysis again confirmed that NaHA may adsorb on the surface of hematite through coordination with surface iron. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of operational parameters on the reverse flotation of Timbopeba itabirite iron ore in a pneumatic (MBE Pneuflot) flotation cell. To this end, the effects of physical and chemical parameters (i.e., collector and depressant dosage, superficial gas velocity (J g), solids concentration, and feed rate) on the reverse flotation of iron ore are investigated in detail. Results show that increasing collector dosage increases quartz recovery, particularly for the coarser quartz where recovery increases by nearly 30%. Increasing depressant dosage results in a decrease in both quartz recovery and hematite loss, for the coarser hematite particles. In addition, increasing the feed rate does not affect quartz recovery or hematite loss, suggesting that the pneumatic flotation cell is not constrained by residence time. Furthermore, increasing the superficial gas velocity results in an increases in quartz recovery to an optimum at a J g of around 0.6 cm/s after which it decreases significantly, particularly for the coarser particles where recovery decreases by 50%. Decreasing the solids concentration does not affect quartz recovery but results in a significant reduction in hematite loss. Here, fine and coarse hematite loss decrease from around 25% to 12% and 10% to 2%, respectively. Solids concentration and J g are operating parameters that have the largest effect on the flotation performance of the pneumatic flotation cell. Overall, the obtained results suggest that this flotation cell should be operated at relatively low superficial gas velocities and solids concentrations. However, these findings are for a pilot scale and would need to be examined at larger scale (e.g., an industrial scale) where different operating conditions may be optimal. [Display omitted] • Evaluation of the reverse flotation of hematite in a pneumatic flotation cell. • Quartz recovery and hematite loss decreases with increasing depressant dosage. • Coarse quartz recovery increases with increasing Jg to an optimum. • Fine hematite loss decreases significantly with decreasing solids concentration. • Physical parameters had the largest effect on the flotation performance (grade and recovery). [ABSTRACT FROM AUTHOR]

Abstract: Reverse flotation of hematite from a local silica sand ore has been investigated using a batch, bench-scale mechanical flotation cell. The effects of various operating parameters such as type and concentration of collectors, type of acid, pH, conditioning time, solid-in-pulp concentration, particle size and temperature have been studied on the hematite removal efficiency by reverse flotation. The results showed that the separation of hematite from silica sand by reverse flotation is possible and good selectivity can be achieved. Experimental data indicate that a larger amount of hematite can be removed from quartz in the presence of hydrochloric acid at elevated temperatures. Also, there exists an optimum collector concentration (Aero 800-series) at which the hematite removal is maximum. A first-order kinetic rate was obtained for the hematite removal from the silica sand. [Copyright &y& Elsevier]

• The hydration structure of quartz and hematite were considered in the calculations. • DDA and CCS are physically adsorbed on the hydrated surface of quartz and hematite. • The selectivity of dodecylamine to quartz is better than that of hematite. • The selectivity of starch to hematite is better than that of quartz. Flotation is one of the most effective methods to selectively separate refractory hematite from quartz. However, the separation mechanism of the hydrophilic minerals of hematite and quartz is still poor understood. In this work, the selective adsorption behaviors of the representative collector dodecylamine (DDA) and depressant causticized cassava starch (CCS) on the hydrated surface of quartz and hematite were systematically investigated based on experimental and computational methods. Accordingly, microflotation results showed that the TFE grade could be significantly improved by increasing the dosage of DDA appropriately, but it had a negative effect on the concentrate recovery, however, with the increase of CCS dosage, concentrate recovery could be improved, but TFE grade could be reduced to a certain extent. Solution-chemistry analysis indicated that the positively charged RNH 3 + was the main component of DDA at pH 7. Because the Zeta potential of quartz is more negative than that of hematite, DDA can be selectively adsorbed on the quartz surface by electrostatic attraction. The DFT calculations showed that the adsorption (inhibition) of starch fragments on the hydrated surface of hematite was stronger than that of quartz, while the collector RNH 3 + had a better selective adsorption interaction with the starch-modified hydrated surface of quartz, resulting in the selective separation of quartz from hematite. This work shed new light on the selective adsorption mechanism of flotation reagents on the hydrated surface of oxide minerals. [ABSTRACT FROM AUTHOR]

[Display omitted] • NaAl contributes to increase the entrainment behavior of fine chlorite. • The hydrogen bond between NaAl and MIBC improved liquid content in foam layer. • NaAl dramatically reduced foam generation time and increased liquid-carrying capacity of bubbles. • Theoretical analysis of Plateau foam structure supports the conclusion of enhanced foam stability by NaAl. • A research idea of improving hematite concentrate by increasing chlorite entrainment behavior is proposed. Hematite reverse flotation pulp is seriously deteriorated by chlorite due to the dissolution of chemical components (e.g., metal ions) on its surface. This study focused on the effect of sodium alginate on hematite reverse flotation. The results indicated that the addition of sodium alginate contributes to improving the chlorite entrainment recovery rate. The results of surface tension and solution viscosity tests along with the foam properties measured by the Foamscan analyzer demonstrated that the foam generation time reduces and the liquid volume in the foam layer increases with the addition of sodium alginate, further increasing the foam stability and chlorite entrainment rate. In addition, theoretical analysis of Plateau's foam structure balance law supports this conclusion. This paper is significant as it addresses the challenging problem of chlorite-containing hematite reverse flotation. [ABSTRACT FROM AUTHOR]

[Display omitted] • DEOSA can remove efficiently quartz from hematite by selectively collecting quartz. • Quartz adsorbs much greater amounts of DEOSA than hematite. • Electrostatic and hydrogen bonding promote the intense DEOSA adsorption on quartz. • Quartz displays high hydrophobicity after DEOSA treatment. Different adsorption behaviors of the collector on the mineral surface play a crucial part in the flotation separation of different minerals by selectively modifying the wettability of mineral surfaces. In this investigation, to effectively remove quartz from hematite via reverse flotation, decaethoxylated stearylamine (DEOSA) was first introduced as a high-performance collector for quartz. The selective collecting performance and differential adsorption mechanisms of DEOSA for both hematite and quartz were studied by flotation experiments and surface analysis. Flotation results suggested that DEOSA displayed excellent collecting capacity for quartz against hematite and the effective removal of quartz from hematite was achieved. Adsorption capacity measurements and surface wettability analysis demonstrated that much larger amounts of DEOSA adsorbed onto quartz than hematite significantly enhanced the quartz surface hydrophobic whether the depressant starch was present or not, which resulted in the excellent flotation performance of quartz. Surface electrical characterization and Fourier transform infrared (FTIR) analysis further proved that the combination of hydrogen bonding and electrostatic attracting force enhanced the strong adsorption of DEOSA onto the quartz, achieving the efficient collection performance of DEOSA for quartz. Based on these findings, DEOSA can be used potentially as a strong-collection and high-performance quartz collector for recovering hematite from quartz via reverse flotation. [ABSTRACT FROM AUTHOR]

• Statistically analyzed the interactive effects of reagents in the presence of nanobubble. • Anionic collector and starch dosages showed the most significant effects. • Nanobubble flotation optimization produced 67.92% Fe grade and 84.73% recovery. The low-grade refractory hematite in Anshan, China is fine disseminated in a huge reserve and its flotation performance is often not satisfactory. In this study reverse flotation experiments statistically designed using Box-Behnken method were carried out with a mechanical flotation cell integrated with nanobubbles and the results were analyzed according to response surface methodology to evaluate the effects and interactions of three independent critical process parameters, i.e., dosages of hematite depressant starch, quartz activator lime, and collector TD-II used in the reverse hematite flotation in the presence of nanobubbles. The results show that with changing for example the starch dosages, nanobubbles improved the iron grade by up to 15% and iron recovery by 10–30%. In addition, TD-II collector and starch had the most significant impact on concentrate iron grade and recovery whereas lime had no direct independent effect over the examined dosage range. The maximum Fe recovery was determined to be 84.73% at a grade of 67.92% at the optimum conditions of 3 kg/t starch, 1.5 kg/t lime, and 0.78 kg/t TD-II collector. The verification tests at optimum conditions established from the contour plots produced approximately the same grade and recovery as statistically predicted. [ABSTRACT FROM AUTHOR]