Cu(II) and Ni(II) activation in the flotation of quartz, lizardite and chlorite

Effect of the Molecular Weight of Carboxymethyl Cellulose on the Flotation of Chlorite

The present study aimed to investigate the influence mechanism of carboxymethyl cellulose (CMC) on the flotation of fine chlorite. To this end, a series of flotation tests, sedimentation tests, and microscope analyses were conducted. Flotation tests revealed an inverse relationship between particle size and the recovery of chlorite, indicating that finer particles exhibited higher recovery rates. Moreover, it was observed that the recovery of fine chlorite was significantly associated with the water recovery (proportion of water entering the floated product to the weight of water in the initial flotation suspension) and a variety of frother types. Based on these findings, it can be inferred that froth entrainment may constitute a crucial component of the recovery mechanism underlying fine chlorite. Thus, reducing froth entrainment (the phenomenon of hydrophilic minerals entering floated products through foam water) is the key to depress chlorite flotation. Flotation tests indicate that fine chlorite recovered into froth products can be depressed effectively by CMC with a high molecular weight. The results of sedimentation tests and microscope analyses in the presence of CMC prove that CMC with a high molecular weight generates flocculation on fine chlorite particles while that with a low molecular weight does not. It is suggested that the depression of chlorite flotation may be attributed to the reduction in the entrainment resulting from the flocculation induced by CMC.

Effects of Interfacial Hydroxylation Microstructure on Quartz Flotation by Sodium Oleate

Quartz, a common inorganic nonmetallic mineral, is usually removed or purified by beneficiation, normally flotation. Given the strong polarity of the quartz surface, it is easy to hydrate to form a hydroxylation layer, which makes it impossible to float quartz with sodium oleate (OL) used alone. An ideal flotation method for quartz is preactivation with Ca²⁺, followed by collection with OL. Herein, the effects of surface hydroxylation on the adsorption of the anionic collector OL on the quartz surface before and after Ca²⁺ activation are systematically investigated by density functional theory (DFT) calculations. The results show that the displacement adsorption of surface hydroxyl substituted by OL^- is not feasible in thermodynamics, and the OL^- can only bind to the H atoms of the hydroxylated quartz surface via hydrogen bonds, namely, hydrogen binding adsorption. Due to the electrostatic repulsion and steric hindrance effect induced by the surface hydroxylation structure, the adsorption ability of OL^- on the quartz surface mediated by hydroxyl bridges is very weak, which is insufficient to realize quartz floating. However, Ca²⁺ ions are easily adsorbed on the hydroxylated quartz surface, providing favorable active sites for subsequent adsorption of OL^-, thus becoming a credible solution for the industrial flotation of the strong hydrophilic mineral quartz. These findings shed some new insights for accurately understanding the flotation mechanism of strongly hydrophilic oxide minerals and are beneficial to promoting the development of mineral flotation fundamentals.

Effects and Mechanism of Fe3+ on Flotation Separation of Feldspar and Epidote with Sodium Oleate at Natural pH

The most common beneficiation method for feldspar is flotation with a cationic (amine) collector under acidic conditions. However, there are several disadvantages to this, such as environmental pollution and equipment corrosion. In order to resolve such problems, it is important to study the flotation of feldspar using anionic collectors under natural pH conditions. The purpose of this paper is to study the effects and mechanism of Fe3+ on flotation separation of feldspar and epidote using sodium oleate (NaOL) at a natural pH. Through flotation experiments, adsorption measurements, zeta potential testing, FTIR analysis and X-ray photoelectron spectroscopy (XPS), the mechanism of Fe3+ on the surface of feldspar and epidote is revealed, and the reason behind the difference in flotation of the two minerals is discussed. The flotation test results show that Fe3+ can significantly improve the flotation behavior of minerals when NaOL is used as a collector under natural pH, and the highest recovery rates of feldspar and epidote are 90% and 43%, respectively. Analysis of the solution and adsorption measurement results show that Fe3+ is adsorbed on the minerals′ surface in the form of Fe(OH)3, which promotes the adsorption of NaOL on the minerals’ surface through Fe(OH)3, activating the flotation of feldspar and epidote. The difference in adsorption of Fe3+ between feldspar and epidote is the reason for this difference in flotation behavior. The results of the zeta potentials show that after being treated with Fe3+, the electrostatic adsorption of NaOL displays a significant negative shift on the surface of feldspar, while there is almost no electrostatic adsorption of NaOL on the surface of Fe3+-treated epidote. FTIR analysis confirmed that the difference in the adsorption of Fe3+ and NaOL on the surface of feldspar and epidote is due to the fact that there are more active particles (metal bonds) on the surface of feldspar than on the surface of epidote, and the properties of these metal bonds can be changed by Fe3+, which allows NaOL to be more easily adsorbed on the mineral surface through –COO−. The possible adsorption form is “mineral-Fe3+–COO−“. Compared with the infrared spectrum of epidote, there is a new absorption peak at 1713.68 cm−1, which can be attributed to the C=O characteristic peak of NaOL in the infrared spectrum of Fe3+–NaOL-treated feldspar, which is why the floatability of feldspar is better than epidote. XPS confirmed that the Fe on the surface of feldspar is Fe3+ in the form of Fe(OH)3, while Fe on the surface of epidote is mainly Fe2O3 (Fe–O) contained in mineral crystals. Furthermore, there is less adsorption of Fe3+ on the surface of epidote, and this discrepancy leads to the difference in the adsorption of NaOL on the minerals’ surface, which itself leads to the difference in flotation behavior between feldspar and epidote. These findings indicate that the flotation separation of feldspar and epidote can be achieved using Fe3+ and NaOL under natural pH. This study may provide a reference for the flotation mechanism of feldspar and epidote under natural pH.

Correlation between Flotation and Rheology of Fine Particle Suspensions

This paper summarizes and discusses previous investigations into the correlation between the rheology and flotation process of fine particle suspensions. This summary provides a better understanding of the challenges and current status of this subject and useful feedback based on the revision of relevant theories and practical implications for fine particle characterization and processing. Such processes include the sustainable beneficiation of complex ores and wastes for valuable material extraction and the segregation of toxic substances. For example, there has been increasing demand for the beneficiation of complex ores often carrying the values (e.g., critical raw materials) in fine grains, due to the noticeable decrease in the accessibility of high-grade and easily extractable ores. To maintain the sustainable use of limited resources, the effective beneficiation of complex ores is urgently required. It can be successfully achieved only with selective particle/mineral dispersion/liberation and the assistance of mineralogical and fine particle characterization including a proper understanding of the rheological behavior of complex ores in the context of fine particle separation/processing. In correlating flotation with suspension rheology, previous works were summarized and we found that the modeling of their correlations as well as comprehensive contributions of pulp and froth rheology on flotation performance have been studied very limitedly, and comprehensive developments in these aspects are thus strongly suggested.

Investigation of the specularite/chlorite separation using chitosan as a novel depressant by direct flotation

Chlorite is one of the representative iron-bearing silicates gangue minerals existed in the specularite ores which the traditional depressants are incapable of action in specularite/chlorite separation flotation. An attempt was conducted for the separation of specularite/chlorite with chitosan as a novel depressant through microflotation tests, Zeta potential measurements, adsorption tests, FT-IR, and XPS analysis. The microflotation results show that chitosan selectively depresses chlorite while specularite still keeps in high floatability. Zeta potential measurements and adsorption tests indicate that chitosan mainly adsorbed on chlorite surface, hindering the subsequent adsorption of dodecan-1-amine and leading the hydrophobicity distinction. The FT-IR spectra of chlorite validate the adsorption of chitosan on chlorite. The results of XPS illustrate that electrons partially transferred from chitosan to the aluminum, iron, magnesium, silicon, and adjacent oxygen atoms of silicon atoms in chlorite during the adsorption process.

Flotation separation of specularite from chlorite using propyl gallate as a collector

Separation of specularite from iron-containing silicate iron ore is challenging due to the similar surface properties of minerals and gangues. In this work, propyl gallate (PG) was applied as a chelating collector to separate specularite from chlorite. The flotation results indicated that collector sodium oleate (NaOL) shows little selectivity for the separation of specularite and chlorite. In contrast, the separation of specularite can be achieved with no depressant required when PG was used as the collector. The optimal separation results were obtained for single mineral flotation with recoveries of 87.11% and 6.98% for specularite and chlorite, respectively, and for mixed mineral flotation with 65.13% TFe grade and 76.28% TFe recovery, when the slurry pH was 8 and PG concentration was 40 mg L⁻¹. FT-IR and XPS analyses indicated that PG could be favorably adsorbed on specularite via phenolic hydroxyl groups, and molecular dynamic simulation results further elucidated the adsorption mechanism. This research suggested that the chelating flotation collector could be effective in the separation of minerals from iron-containing silicate iron ores.

Separation of specularite from iron-containing silicate iron ore is challenging due to the similar surface properties of minerals and gangues.

A Study of Temperature Effect on the Xanthate’s Performance during Chalcopyrite Flotation

A multi-scale investigation was conducted to study the surface properties of xanthate-absorbed chalcopyrite at elevated temperature to understand the temperature effect on the xanthate’s performance during chalcopyrite flotation. Firstly, a macro-scale study was initiated to investigate the temperature effect on the hydrophobicity of mineral surface by means of contact angle measurement, Hallimond tube microflotation and lab flotation tests; secondly, a micro–scale study was conducted to clarify the temperature effect on the adsorption of chemicals on mineral surface employing an atomic force microscope (AFM) and Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR). In the experiments, pure chalcopyrite samples were used for contact angle measurement, Hallimond tube microflotation, AFM and FTIR; and copper ore samples (1.51% Cu, 5.88% Fe 0.029% Mo, 5.23% S in weight percentage) were used for lab flotation tests. FTIR spectra and AFM images showed that, when potassium amyl xanthate (PAX) was used as the collector in this study, oily dixanthogen was the main hydrophobic species on the chalcopyrite surface. The morphological change of dixanthogen patches at elevated temperatures has a more significant impact than changes in the amount of adsorption species. Increasing temperature within a certain range is beneficial for the collector’s performance by increasing flotation recovery.

The Effect of Sodium Alginate on Chlorite and Serpentine in Chalcopyrite Flotation

Chlorite and serpentine are common magnesium-containing gangue minerals in copper sulfide flotation. In this study, sodium alginate, a natural hydrophilic polysaccharide, was introduced as a selective depressant for these gangue minerals. Micro-flotation tests were conducted on both single minerals and synthetic mixtures. The flotation results showed that sodium alginate could simultaneously depress the flotation of chlorite and serpentine effectively, but seldom influenced the floatability of chalcopyrite at pH 9. In the ternary mixture flotation, a concentrate with a Cu grade of 31% could be achieved at Cu recovery of 90%. The selective depression of chlorite and serpentine was also validated by the real ore flotation experiments. The selective depression mechanism was investigated through adsorption tests, zeta potential measurements, and FTIR analyses. The adsorption density results implied that sodium alginate selectively adsorbed on the surface of phyllosilicates, but no adsorption on the chalcopyrite surface was observed. The zeta potential results showed that the sodium alginate could selectively decrease the surface charge of chlorite and serpentine. The FTIR results revealed the chemical adsorption of sodium alginate on the chlorite and serpentine surface and no form of adsorption on chalcopyrite, agreeing well with the adsorption density results. On the basis of these results, a selective adsorption model of sodium alginate on the mineral surface was proposed.

Beneficiation and Purification of Tungsten and Cassiterite Minerals Using Pb–BHA Complexes Flotation and Centrifugal Separation

Pb–BHA complexes have been shown to be selective for the separation of tungsten and cassiterite minerals from calcium minerals. These minerals could be enriched synchronously to some extent using Pb–BHA complexes flotation. However, it is difficult to further improve the quality and recovery of the scheelite, wolframite, and cassiterite concentrate due to their different behavior in flotation, such as flotation rate and sensitivities to depressants. Moreover, the super fine particles create some challenges for the cleaning flotation process. In this study, advanced gravity separators for super fine particles were introduced for the cleaning process based on the slight difference in the specific gravity of scheelite, wolframite, and cassiterite. The new process featured pre-enrichment using Pb–BHA flotation, and upgrading using gravity separation, taking into account both the similarities and differences in floatability and density of the different minerals. The grades of WO3 and Sn in the concentrate of the new process reached to 61% and 2.89%, respectively, and the recovery of Sn was significantly improved. In addition, gravity separation is highly efficient, cost effective, and chemical-free, which is environmentally friendly. This study has proven that physical separation can be used for the purification of flotation products and provide some solutions for separation problems of complex refractory ores, which has, up until now, been rarely reported in the literature and/or applied in mineral processing.

The Effect of New Modified Fatty Acid (CY-23) Collector on Chlorite/Hematite Separation

The flotation separation on chlorite and hematite with the new modified fatty acid collector CY-23 was studied. The investigation included both flotation and reagent adsorption tests. And all the characteristics of chlorite surface before and after the adsorption of new collector CY-23 have been studied with X-ray photoelectron spectroscopy (XPS). The flotation results showed that caustic starch (CS) could depress the flotation of hematite and chlorite and CaCl2 could activate chlorite flotation but failed on hematite when using CY-23 as collector. The adsorption rate of CY-23 on the surface of chlorite after being inhibited by CS was relatively smaller, but the amount of CY-23 adsorbed on the inhibited chlorite was greatly increased after adding activator CaCl2. The results of XPS analysis showed that the photoelectron spectroscopy peaks of Mg2p and Al2p moved towards low energy after collector CY-23 was absorbed on chlorite surface, which indicated that chemical bonding through electron cloud transfer occurred between collector CY-23 and Mg, Al ions of chlorite surface. The chemical reaction promoted the adsorption of CY-23 on chlorite surface and eventually improved the ability of CY-23 to float and collect chlorite.

A review of zinc oxide mineral beneficiation using flotation method

In recent years, extraction of zinc from low-grade mining tailings of oxidized zinc has been a matter of discussion. This is a material which can be processed by flotation and acid-leaching methods. Owing to the similarities in the physicochemical and surface chemistry of the constituent minerals, separation of zinc oxide minerals from their gangues by flotation is an extremely complex process. It appears that selective leaching is a promising method for the beneficiation of this type of ore. However, with the high consumption of leaching acid, the treatment of low-grade oxidized zinc ores by hydrometallurgical methods is expensive and complex. Hence, it is best to pre-concentrate low-grade oxidized zinc by flotation and then to employ hydrometallurgical methods. This paper presents a critical review on the zinc oxide mineral flotation technique. In this paper, the various flotation methods of zinc oxide minerals which have been proposed in the literature have been detailed with the aim of identifying the important factors involved in the flotation process. The various aspects of recovery of zinc from these minerals are also dealt with here. The literature indicates that the collector type, sulfidizing agent, pH regulator, depressants and dispersants types, temperature, solid pulp concentration, and desliming are important parameters in the process. The range and optimum values of these parameters, as also the adsorption mechanism, together with the resultant flotation of the zinc oxide minerals reported in the literature are summarized and highlighted in the paper. This review presents a comprehensive scientific guide to the effectiveness of flotation strategy.

Effects of Some Multivalent Ions on Coagulation and Electrokinetic Behaviours of Colemanite Particles

The effects of magnesium, barium, aluminium, and ferric cations as multivalent ions on the coagulation and electrokinetic behaviours of colemanite have been investigated in relation to pH and cation concentration. The zero point of charge for colemanite was determined to be at pH 10.2. The positive surface charge of colemanite increased in the presence of multivalent ions at pH values below the zero point of charge. Also, these ions changed the zeta potential of colemanite from negative to positive within the pH range 10.2 to 12. In the experiments, the coagulation of colemanite with ferric ions was more efficient than with the other ions and the effect of ferric ions varied considerably depending on the concentration and pH. The coagulation recovery values of colemanite suspension increased quickly up to 2.5 × 10–3 M concentration of ferric ions and the maximum value (~93 %) was obtained at a pH of 11.5. It was also found that the coagulation behaviour of the colemanite suspension in the presence of multivalent cations was in good agreement with the electrokinetic characteristics.

Surface charge and wetting characteristics of layered silicate minerals

The surface characteristics, including surface charge and wettability, of layered silicates are reviewed based on experimental results and molecular dynamics simulation (MDS) results. The surface charge features of important layered silicates including mica, talc, and kaolinite are described from atomic force microscopy (AFM) measurements, electrophoresis measurements, and/or results from potentiometric titration. In addition, the wetting characteristics of the silica tetrahedral surface which is common to all layered silicates are examined with different experimental techniques and results are discussed. The wettability of trilayer silicates and bilayer silicates is discussed, particularly the wettability of the silica tetrahedral face and alumina octahedral face of kaolinite based on MDS results as well as recent AFM results.

Effects of heavy metals and oxalate on the zeta potential of magnetite

Zeta potential is a function of surface coverage by charged species at a given pH, and it is theoretically determined by the activity of the species in solution. The zeta potentials of particles occurring in soils, such as clay and iron oxide minerals, directly affect the efficiency of the electrokinetic soil remediation. In this study, zeta potential of natural magnetite was studied by conducting electrophoretic mobility measurements in single and binary solution systems. It was shown that adsorption of charged species of Co(2+), Ni(2+), Cu(2+), Zn(2+), Pb(2+), and Cd(2+) and precipitation of their hydroxides at the mineral surface are dominant processes in the charging of the surface in high alkaline suspensions. Taking Pb(2+) as an example, three different mechanisms were proposed for its effect on the surface charge: if pH<5, competitive adsorption with H(3)O(+); if 5<pH<6, adsorption and surface precipitation; and if pH>6, precipitation of heavy metal hydroxides prevails. Oxalate anion changed the associated surface charge by neutralizing surface positive charges by complexing with iron at the surface, and ultimately reversed the surface to a negative zeta potential. Therefore the adsorption ability of heavy metal ions ultimately changed in the presence of oxalate ion. The changes in the zeta potentials of the magnetite suspensions with solution pH before and after adsorption were utilized to estimate the adsorption ability of heavy metal ions. The mechanisms for heavy metals and oxalate adsorption on magnetite were discussed in the view of the experimental results and published data.