Flotation Results Research Articles

Synthesis of Hydroxylated Xanthate Salt and Its Use as Novel Selective Depressant in Copper-Molybdenum Separation

A hydroxylated xanthate salt (HXS) was synthesized from ethanol, carbon disulfide, and NaOH. The flotation responses of chalcopyrite and molybdenite when HXS was used as a novel depressant were investigated using bench-scale flotation tests. The bench-scale flotation results indicate that HXS strongly influenced the flotation of chalcopyrite and had little effect on the flotation of molybdenite. These results can be attributed to a significant improvement in the molybdenite/chalcopyrite selectivity surface index after the addition of HXS. The synthesized HXS contained both solid-philic and hydrophilic groups. The molybdenum recovery achieved using HXS was 9.91% higher than that obtained using sodium hydrosulfide, and better separation was achieved. Compared with sodium hydrosulfite, the chemical oxygen demand, sulfates and five-day BOD decreased significantly using the alternative depressant. This HXS is therefore a potential depressant for use in copper-molybdenum separation.

Exploration on the mechanism of enhancing low-rank coal flotation with cationic surfactant in the presence of oily collector

It is difficult to yield a high combustible matter recovery in the flotation of low rank coal with common oily collectors. This study focuses on the enhancement in flotation performance of low rank coal by combining diesel oil with didodecyldimethylammonium bromide (DDAB), as well as its corresponding intensifying mechanism. The adsorption of DDAB and/or diesel oil on the pure coal and quartz surfaces was investigated based on the zeta potential and FTIR analyses, while the floatability of the coal and quartz samples before and after pretreatment was evaluated by the attachment time and flotation results. The results indicated that DDAB had great effects on the zeta potentials of coal and quartz, and the isoelectric points of these two samples were observed at the DDAB concentrations of about 0.007 and 0.006 g/L, respectively. Additionally, according to the FTIR analyses, the physical and chemical adsorptions were proposed to interpret the adsorption of DDAB, and diesel oil and mixed diesel oil/DDAB on the coal surface, respectively. Meanwhile, the diesel oil’s adsorption of on the coal surface was enhanced by the conditioning process with the mixed DDAB/diesel oil. In contrast, diesel oil adsorption on the quartz was very little in quantity. As a result, a great difference in surface hydrophobicity between the coal and the quartz was attained, and an excellent flotation performance was obtained by using the mixed DDAB/diesel oil. However, a too low surface tension of flotation pulp caused by the excessive DDAB seems to be unfavorable to the flotation of coal samples. In this case, water with less surface tension was readier to spread on the coal surface than diesel oil, thereby making the coal hydrophilic and meanwhile hindering the diesel oil’s spreading on its surface.

Selective flotation of chalcopyrite and molybdenite using H2O2 oxidation method with the addition of ferrous sulfate

Hydrogen peroxide (H2O2) has been used as an oxidizing agent in the selective flotation of chalcopyrite and molybdenite. However, this method required relatively high concentration of H2O2 to deliver flotation results (i.e., mineral grades and recoveries) comparable to those obtained by the conventional copper-molybdenum (Cu-Mo) ores flotation using sodium hydrosulfide (NaHS). Therefore, further improvements are needed to reduce the consumption of H2O2 reagent. In this study, ferrous sulfate (FeSO4) was used to enhance the oxidation performance of H2O2 through Fenton-like reactions. Flotation results showed that the consumption of H2O2 reagent could be reduced by the addition of FeSO4 without losing the flotation selectivity. The reason might be caused by increasing of oxidation performance as indicated by the increasing concentration of dissolved oxygen after the addition of FeSO4 into the H2O2 aqueous solution. Surface analysis using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) images showed that the surface of chalcopyrite was covered by more hydrophilic precipitates after the oxidation treatment using H2O2 aqueous solution with the addition of FeSO4, thus more hydrophilic surface and lower floatability. On the other hand, the surface of molybdenite was slightly oxidized and its surface remained hydrophobic as confirmed from contact angle results. Flotation tests using Cu-Mo bulk concentrate demonstrated that selective flotation might be possible using a mixture of FeSO4 and H2O2 aqueous solution. Moreover, this new method could be used as an alternative to copper depressant in Cu-Mo selective flotation, replacing the NaHS reagent.

Adsorption of bis(2-hydroxy-3-chloropropyl) dodecylamine on quartz surface and its implication on flotation

Abstract In order to clarify the effect of polar group modification on flotation performance of amine collector, flotation properties of quartz and hematite using bis(2-hydroxy-3-chloropropyl) dodecylamine (N23) as a collector were investigated. And the adsorption mechanism of N23 on quartz surface was established by zeta potential measurements, SEM/EDS measurements, and molecular structure analysis. Single mineral flotation results indicated that N23 showed stronger collecting ability on quartz and hematite than DDA-CH 3 COOH. However, starch could depress the flotation of hematite. Flotation recovery of 98.10% for quartz could be achieved, when N23 concentration was 43.33 mg/L and starch concentration was 16.67 mg/L at natural slurry pH. Separation of artificially mixed minerals of hematite and quartz was achieved effectively using N23 as the collector. The optimized separation result with 66.29% iron grade and 90.06% iron recovery in concentrate was obtained when slurry pH was 7.34 with 43.33 mg/L N23 and 23.33 mg/L starch. The interaction energies of N23 with mineral surface also showed well consistency with flotation results. SEM/EDS analyses and zeta potential measurements revealed that N23 could absorb on quartz surface in the forms of strong electrostatic and hydrogen bonding interaction. Compared with DDA, N23 had a higher HLB value and better water-solubility, which resulted in better dispersion in water and stronger adsorption on mineral surface.

Effects of ultrasonic pretreatment on the flotation performance and surface properties of coking middlings

ABSTRACTThe effects of ultrasonic pretreatment on the flotation performance of coking middlings were investigated through a flotation cell. The surface properties of coking middlings before and after ultrasonic pretreatment were indicated using X-ray fluorescence analyzer (XRF), scanning electron microscope (SEM) and DSA100 contact angle analyzer. The flotation results demonstrated that the combustible recovery increased by 7.18%, while the ash value of flotation tailings decreased by 2.74% at most after ultrasonic pretreatment. Flotation results were supported by XRF analysis, SEM analysis, and contact angle measurements results. These results show that the ultrasonic pretreatment has a beneficial influence on the flotation of coking middlings.

Intensify dodecylamine adsorption on magnesite and dolomite surfaces by monohydric alcohols

The flotation of magnesite and dolomite were investigated with the presence of single dodecylamine (DDA) and combined mixtures of DDA and monohydric alcohols, respectively. The adsorption behavior of DDA, butanol, hexanol and octanol on the surface of the two minerals were shown by molecular dynamics simulation, and the results were corresponding with the analysis of zeta potential, measurements of the contact angle and adsorption. Flotation results indicated that part of DDA could be replaced by the three alcohols (butanol, hexanol, octanol) to get better flotation results. Molecular dynamics simulation and the results of zeta potential and contact angle measurements indicated that adsorption of DDA on mineral surfaces could be strengthened by monohydric alcohols.

Utilization of sodium humate as selective depressants for calcite on the flotation of scheelite

ABSTRACTThe flotation separation of scheelite from calcite using sodium humate (SH) as a potential depressant has been studied through micro-flotation experiments, zeta potential and Fourier transform infrared (FT-IR) spectra measurements. The flotation results indicate SH exhibited selective depression effect on calcite in the presence of sodium oleate, achieving the flotation separation of scheelite from calcite. Zeta potential results indicate that SH strongly absorbed on calcite surface but negligibly on scheelite surface, which prevents the adsorption of sodium oleate on calcite surface. The FT-IR results also show that SH can be adsorb on the surface of calcite. Results shown a higher Ca density on the calcite than on scheelite surface, and that calcite can accommodate the interaction of SH.

Impeller Radial Velocity and Air Flow Rate Influence on Copper Rougher Flotation Recovery

A rougher flotation study has been done to analyze the effects of copper feed mineralogy, air flow rate and impeller radial velocity on metallurgical performance. During the performance testing the trials were exposed to metallurgical examining and computerised mineral analysis to establish a size-by-size mineralogy. The mineralogical and metallurgical information was compared to the material balance for rougher flotation results. These samples showed that copper recovery optimization should focus on the losses of liberated Cu-minerals and how they are associated with fine particles. The result of variable impeller radial velocity for each flotation cell cascade on metallurgical performance has been explored on a known-sized and an unknown-sized base, to gauge the input from the fine particles. An industrial application is discussed in this paper, and it validates that divergence of the impeller radial velocity and air flow has positive influence on the recovery.

Comparative separation analysis of direct and reverse flotation of dolomite fines

ABSTRACTIn the present investigation, beneficiation of a low-grade dolomite fines was carried out with the aim to remove the siliceous gangue content. Extensive experimental studies on direct and reverse flotation were carried out on low-grade ore by varying the critical process variables, and the performance was compared. The experimental results show that it is possible to reduce the silica content following both direct and reverse flotation processes. Further, direct flotation results show better control over the quality of the product while reverse flotation has an edge on the product yield.

Ultrasonic flotation cleaning of high-ash lignite and its mechanism

Lignite, as a low rank coal reserve plays an important role in energy supply. However, fine lignite is difficult to upgrade using the conventional flotation because of its high surface hydrophilicity. This investigation was to enhance the flotation recovery of high-ash lignite combined with wet-screening, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and induction time measurer to reveal the mechanism of simultaneous ultrasonic treatment enhancing the lignite flotation. Flotation results indicate the clean coal yield is greatly increased whereas the clean coal ash content is highly reduced by simultaneous ultrasonic flotation compared with the conventional flotation. SEM and XPS results show coal surface is physically cleaned and hence the clay coating is reduced by simultaneous ultrasonic flotation. The removal of high-ash mineral particles from coal surface benefits the coal-bubble attachment. Furthermore, ultrasonic treatment creates many micro-bubbles that enhance the floatability of lignite through micro-bubble-based coating on coal surface. The micro-bubbles play a bridging role in the coal-bubble attachment. The water film on lignite surface may be also unstable and easy to rupture during bubble-coal attachment under the condition of ultrasonic treatment.

Investigation of Effects of Nanobubbles on Phosphate Ore Flotation

Phosphorous is vital for life, including plants, animals, and human beings and it is an essential component in agricultural fertilizers and phosphorous-based chemicals. Phosphate ores, mainly in the form of apatite and collophanite, are non-renewable natural resources of phosphorus. Froth flotation has been used in the phosphate industry for more than half a century as the primary technique for upgrading phosphate. Nevertheless, flotation does not produce satisfactory performance for phosphate beneficiation in many cases, especially for very fine and coarse phosphate particles. This study was performed with an aim to develop a nanobubble enhanced flotation process to enhance phosphate flotation efficiency. A specially designed flotation column featured with a nanobubble generator and a conventional bubble generator was employed to assess the effects of nanobubbles on the phosphate ore flotation performance under different operating conditions. Flotation process parameters investigated include feed flow rate, dosage of collector, dosage of frother, flotation time, etc. The flotation results have shown that use of nanobubbles increased P 2 O 5 recovery by up to 30% for a given Acid Insoluble (A.I.) rejection, depending on phosphate concentrate grade. Nanobubbles reduced the collector and frother dosage by about 50% and also increased flotation kinetics. The improved flotation performance can be attributed to increased collection efficiency and surface hydrophobicity in the presence of nanobubbles.

Multidimensional Analysis of Copper Ore Flotation in Terms of Applied Hydrophobizing Agents

Flotation is a method of enrichment used to distribute particles, which differ in their surface properties. Hydrophobic solids intrinsically create contact at the solid-liquid-gas interface. However, not all minerals, including copper minerals, can be characterized by this crucial ability. In that case it is necessary to use the collector reagents which guarantees a high efficiency of the enrichment process. The main aim of the paper was to examine the impact of selected collector types and dosages on the results of Polish sandstone copper ore flotation and to find optimal parameter values for products that meet quality and quantity requirements. The laboratory tests were carried out with an application of two types of collectors (Hostaflot, sodium ethyl xanthate aqueous solution) in dosages 100 and 150 g/Mg. Data analysis was based on the use of the taxonomy methods in order to select optimal conditions of collector dosage and type. Based on the indexes, it was found that the best enrichment effects were obtained with a sodium ethyl xanthate aqueous solution 150 g/Mg.

Non-first-order Kinetics Modelling Method for Stibnite Flotation Process

As the mineral particle size and the drug effect are not uniform, resulting in a single flotation rate constant cannot describe the flotation process accurately. In this paper, based on the results of stibnite batch flotation, the non-first-order kinetic model is proposed to describe the stibnite flotation process. Based on the quadratic orthogonal regression requirements, the collector, pH adjuster and stirring rate were selected as the experimental factors, and the test combination was designed. Aiming at the characteristics of flotation rate constant with time, this paper presents a non-first-order kinetic model of stibnite batch flotation using double exponential function to describe the change of flotation rate constant. With the aim of minimizing the prediction error of recovery rate, the differential evolution algorithm is used to realize the off-line identification of the flotation rate change function. Compared with the first-order kinetics method, the proposed piecewise linear model can better describe and predict the flotation kinetics curve of stibnite.

Effects of monohydric alcohols on the flotation of magnesite and dolomite by sodium oleate

Part of NaOL (sodium oleate) was replaced with different monohydric alcohols (butanol, hexanol, and octanol) in the flotation of magnesite and dolomite for lower flotation costs and higher flotation efficiency. Zeta potential analyses, contact angle measurements and molecular simulations were used to investigate mechanisms of the adsorption of alcohols. Single mineral flotation tests showed that combined reagents could produce better flotation results than single NaOL. Contact angles and zeta potentials of the two minerals indicated that alcohols were adsorbed on mineral surfaces physically and improved the hydrophobicity when combined with NaOL. Molecular dynamics simulation was used to explore mechanisms of alcohols at the molecular level. Different adsorption models indicated that alcohols could increase NaOL density and the thickness of the hydrophobic layer on both mineral surfaces. As a result, the flotation of magnesite and dolomite was enhanced. Based on molecular dynamics calculation, the adsorption mode of octanol on mineral surfaces, when combined with NaOL for flotation, was shown to be adsorbed through hydrogen bonds.

Research on cationic surfactant adsorption performance on different density lignite particles by XPS nitrogen analysis

Lignite is well known for its hard-to-float property. Many surfactants, including anionic, cationic and non-ionic have been applied to improve the floatation efficiency. In this work, cationic dodecylamine was applied to pretreat the lignite samples with different densities, which are −1.45 g/cm3, 1.45–1.80 g/cm3 and +1.80 g/cm3. The surface charged properties of the raw samples were determined by a zeta potential analyzer. The adsorption performance was characterized by XPS and UV/VIS spectrophotometer methods. From the surface zeta-potential results, three curves of zeta-potential figures versus pH value are similar to each other qualitatively in the pH range 5–8, which indicates that the organic structure has the similar ionization/ protonation ability with inorganic minerals at neutral pH. The negatively charged surfaces attract the cationic dodecylamine molecules at neutral pH for the three density fractions, which is shown by the XPS narrow sweep of heteroatom nitrogen before and after the pretreatment process. On the lignite surface, nitrogen was mainly existed in two forms of pyrrolic and quaternary. After the pretreatment, the quaternary-N peak was increased on the lignite surface due to the adsorption of dodecylamine molecules, especially on the surface of the highest density fraction. Correspondingly, UV/VIS spectrophotometer results showed that the adsorption amounts of dodecylamine molecules were 11.4, 18.7 and 20.0 mg/g on the surface of the samples from low to high density. On the other hand, the flotation result showed that more high ash particles and some low ash ones were both floated with the increase of dodecylamine dosage. Hence, if dodecylamine is to be used in lignite flotation, reagents should be added to selectively depress the adsorption process of cationic dodecylamine on the low or high ash particles.

Flotation separation of scheelite from calcite using mixed collectors

Flotation separation of scheelite from calcite is difficult due to the similarities in their surface properties. In this work, the flotation behavior of scheelite and calcite using oxidized paraffin soap (OPS), benzohydroxamic acid (BHA) and the mixed OPS/BHA collectors was investigated through micro-flotation experiments. The flotation results of single mineral experiments demonstrated a higher selectivity for the flotation of scheelite from calcite at pH9 than individual OPS and BHA when using water glass as depressant. In order to probe the validity of the findings, mixed binary minerals experiments, contact angle and zeta potential experiments were also carried out successfully.

Recovery of molybdenum and copper from porphyry ore via iso-flotability flotation

Abstract A copper–molybdenum iso-flotability flotation process has been developed to efficiently improve the recovery of molybdenite from Duobaoshan porphyry Cu–Mo ores. The effects of flotation approach, type of collector, feed particle size distribution, rougher pH value and reagent dosage on the recovery of molybdenite were evaluated systematically. The results suggest that compared with kerosene and diesel oil, transformer oil has stronger dispersion capability in water media and better flotation selectivity for molybdenite, providing a higher molybdenum recovery under low reagent dosage. Moreover, compared with bulk flotation approach, the iso-flotability flotation approach using transformer oil as a collector can obtain superior Mo recovery (90.77%) and grade (0.80%) in the cleaner concentrate, and increase the Mo recovery and grade by over 18% and 5% in the final Mo concentrate, respectively. The results of commercial flotation further indicate that the iso-flotability flotation approach is a rational and effective route to beneficiate the porphyry Cu–Mo ores.

Further Investigations on Simultaneous Ultrasonic Coal Flotation

This study investigates the flotation performance of a representative hard coal slime sample (d80 particle size of minus 0.2 mm) obtained from the Prosper-Haniel coal preparation plant located in Bottrop, Germany. Flotation was carried out with a newly designed flotation cell refurbished from an old ultrasonic cleaning bath (2.5 L volume) equipped with a single frequency (35 kHz) and two different power levels (80–160 W) and a sub-aeration-type flotation machine operating at a stable impeller speed (1200 rpm) and air rate (2.5 L/min). The reagent combination for conventional and simultaneous ultrasonic coal flotation tests was Ekofol-440 at variable dosages (40–300 g/t) with controlling water temperature (20–25 °C) at natural pH (6.5–7.0). The batch coal flotation results were analyzed by comparing the combustible recovery (%) and separation efficiency (%) values, taking mass yield and ash concentrations of the froths and tailings into account. It was found that simultaneous ultrasonic coal flotation increased yield and recovery values of the floated products with lower ash values than the conventional flotation despite using similar reagent dosages. Furthermore, particle size distribution of the ultrasonically treated and untreated coals was measured. Finely distributed coal particles seemed to be agglomerated during the ultrasonic treatment, while ash-forming slimes were removed by hydrodynamic cavitation.

Effect of grinding media on the surface property and flotation behavior of scheelite particles

Grinding for mineral liberation is a prerequisite for a successful flotation separation. Different grinding media produce mineral particles with different surface properties and flotability. In this study, the surface properties and flotation behavior of scheelite particles having a size of −74+38μm produced by ball and rod mills were studied through single mineral flotation experiment, scanning electron microscopy (SEM) observation, wettability measurement, and X-ray diffraction (XRD) test. The wettability and flotation results showed that, compared to the ball mill particles, the rod mill ones have a lower critical surface tension and thus a greater hydrophobicity when treated with the collector solution, and accordingly perform a better flotation recovery using oleate as the collector. In addition, the rod mill particles have a smaller specific surface area, so the full monolayer adsorption of the collector on their surfaces is achieved at a lower oleate concentration. The SEM analysis further confirmed that mineral grains obtained from the rod mill possess larger elongation and flatness values, which are essentially required for their attachment with air bubbles. The XRD observations revealed that mineral particles from both mills (i.e. ball and rod) have similar exposure intensity of abundant {112} surface. However, the rod mill particles have more {101} surface exposed, while the ball mill particles have more {001} surface exposed, leading to a stronger interaction of the collector with the rod mill particles. Keeping in view the stronger interaction with the collector and the easier attachment to air bubbles, the rod mill scheelite particles are deemed to be more hydrophobic and have a higher flotation recovery. These details studied will help establish the relation between the particle surface properties and the grinding media, and provide guidance for optimizing flotation separation.

A comparison study of adsorption of benzohydroxamic acid and amyl xanthate on smithsonite with dodecylamine as co-collector

The objective of this paper is to display the results of the flotation and adsorption behaviors of benzohydroxamic acid (BHA), potassium amyl xanthate (KAX), dodecylamine- hydrochloride (DDA), mixed BHA/DDA and KAX/DDA on smithsonite. The flotation results show a collecting ability sequence of BHA>KAX>DDA on smithsonite and the best flotation performance at mixing ratio of 1:4mol fraction DDA/KAX for mixed collector on smithsonite. The enhancement of smithsonite recovery by co-adsorption of KAX and DDA, while no promotion effect as to mixed BHA/DDA catanionic system, are attributed to the difference in steric effect of absorbed head group. According to the results of zeta potential and contact angle (CA) measurements, a most negative charged and the highest hydrophobic smithsonite surface are attained using KAX with DDA as co-collector, which shows a good agreement with the flotation results. FTIR measurements display the stabilization against oxidation and decomposition of DDA on KAX and the inhibition of preferential adsorbed BHA ions on DDA adsorption. The interaction energies of single and mixed collectors with mineral surface also shows well consistency with experimental results. The adsorption models proposed illustrate the decrease in the electrostatic head–head repulsion and the increase in lateral tail–tail hydrophobic interaction between adjacent KAX anions due to the insertion of DDA cations, while almost no DDA could access to smithsonite surface through adjacent BHA owing to steric effect.