Flotation Recovery Research Articles

Application of the response surface method (RSM) based on central composite design (CCD) and design space (DS) to optimize the flotation and the desliming conditions in the recovery of PGMs from mine sludge

ABSTRACT This investigation focuses on the application of the response surface methodology (RSM) through central composite design (CCD) and design space (DS) to study and optimize the desliming impact on the flotation recovery of platinum group metals (PGMs) from mine sludge. The correlation between independent and dependent variables were determined. pH and pulping effect for the desliming and pH, MIBX, CuSO4, (NH4)2SO4, mixt depressants, and flotation time for the flotation were investigated to evaluate PGMs recovery and grade as responses. The desliming and flotation sensibilities through ANOVA were assessed. Suitable models for predicting the optimum operating conditions, parameter contributions and interactions during PGMs recovery and Design Space were generated. A satisfactory recovery of 79% (17.82 g/ton PGMs) was obtained after the desliming at optimum pH and pulp density of 10.29 and 25.08 Wt.%, while a satisfactory recovery of 39% (45 g/ton PGMs) was obtained after rougher flotation at optimum pH of 9.94 with MIBX, CuSO4, (NH4)2SO4, mixt depressants of 150.51, 39.697, 60, and 50 g/ton, respectively. Results revealed that RSM through the SSD and the DS play a significant role in monitoring the desliming and flotation process by showing impacting parameters, degree of contribution and correlation within parameters.

Protein enrichment by foam Fractionation: Experiment and modeling

• BSA protein adsorbs irreversibly on the bubble interface. • A surface equation of state was provided for BSA using surface compression tests. • The rising bubble was emulated through flow-on-bubble experiments. • Foam coalescence accelerates the liquid drainage leading to higher protein enrichment. • A modeling was proposed to estimate recovery and grade in protein flotation. This work investigates the enrichment of bovine serum albumin (BSA) protein through foam fractionation. Here, we performed experiments using BSA and measured the recovery and grade of the extract. Additionally, an unsteady-state simulation of the protein foam fractionation process was carried out by numerically solving the liquid drainage equation in the foam. Thereby, the extracted liquid volume and protein concentration were calculated. Required quantities such as foam stability, interface coverage or bubble size distribution were measured in corresponding experiments and were fed into the model. The experiments showed that the foam coalescence accelerates the liquid drainage leading to dryer extract and higher protein enrichment. The modeling also reproduced the liquid recovery and extract concentration of the foam fractionation tests within a reasonable error range. The modeling solely relies on experimental inputs and does not require any tuning parameters. It can be further used for optimization or up-scaling of protein foam fractionation.

Enhancing the floatability of smithsonite mixed with silicate minerals by using a novel dispersant of cetylpyridinium bromide

Silicate minerals often coexist in nonferrous metal ores. In the flotation process, the fine clay particles are easy to slime-coating on the target mineral surface and lead to the deterioration of the flotation efficiency. In this study, the flotation behaviors of single smithsonite and its mixture with fine kaolin or chlorite were studied using octadecvlamine acetate (OCTA) as the collector. It was found that the single mineral of smithsonite had a high flotation recovery, while the mixed minerals of smithsonite with kaolin or chlorite possessed a poor processability. To eliminate the adverse effect of kaolin and chlorite on the floatability of smithsonite, a cetylpyridinium bromide (CPB) was introduced in the flotation process as a novel dispersant. The micro-flotation results showed that the addition of CPB greatly improved the separation efficiency of smithsonite from the mixed ores. It was believed that the adsorption of CPB on the surface of kaolin and chlorite eliminated the hydrophobic attractive force between the smithsonite and clay particles and thus prevented the slime-coating of kaolin and chlorite on the smithsonite surface. As a result, the floatability of smithsonite mixed with kaolin or chlorite was greatly enhanced. This work deepens our understanding of the flotation process of nonferrous metal ores mixed with fine clay minerals, and provides a novel dispersant of CPB which is expected to be applied in the flotation separation of mixed ores.

Effect of deep oxidation of chalcopyrite on surface properties and flotation performance

In this study, chalcopyrite was oxidized in hydrogen peroxide (H 2 O 2 ) solutions of different concentrations to simulate different degrees of oxidation in real ores, and the effects of H 2 O 2 treatment on chalcopyrite surface properties and flotation performance were investigated by surface analysis techniques and floatation experiments, which implied the reason for the poor grade and recovery of oxidized chalcopyrite concentrate in the production process of the ore. Flotation results showed that when the concentration of H 2 O 2 increased from 0% (by weight) to 5%, the flotation recovery of chalcopyrite decreased sharply. However, with increasing H 2 O 2 concentration from 5% to 30%, chalcopyrite recovery improved relatively to different degrees with different collector concentrations. Analyses of X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma-atomic optical emission spectrophotometry (ICP-OES) results indicated that the pretreatment with H 2 O 2 caused that hydrophilic substance formed on chalcopyrite surface with the dissolution of copper ions, and the dissolution amount of copper increased with the increase of H 2 O 2 concentration. UV–visible spectrophotometer and Fourier Transform Infrared spectrum (FTIR) studies indicated that the pretreatment of chalcopyrite with H 2 O 2 had little effect on the adsorption amount of potassium butyl xanthate (PBX) on chalcopyrite surface. However, due to the dissolution of copper ions, PBX interacted with chalcopyrite mainly as buthyl dixanthogen (BX) 2 .

Enhanced fine flake graphite flotation and reduced carbon emission by a novel water-in-oil kerosene emulsion

Kerosene is a frequently-used collector in graphite flotation; however, its consumption substantially increases due to its poor dispersibility in water and the depletion of graphite resources. We prepared a novel water-in-oil type kerosene emulsion as a more efficient collector for graphite flotation. The effect of preparation parameters on the emulsion stability was investigated by particle size analysis, stratification test, and electrical conductivity test. The results indicated that particle size played a dominant role in the stability of emulsified kerosene. The smaller emulsified kerosene droplets contribute to a more stable emulsion dispersion. Optical microscope and Cryo-SEM techniques visualized a stable and homogenous emulsion with an average particle size of 1–2 µm. Furthermore, batch flotation and adsorption tests indicated that the emulsified kerosene outperformed pristine kerosene as a collector in fine flake graphite flotation, increasing the flotation recovery by approximately 3%, with 26%− 34% kerosene consumption reduction. Our study provides a valuable pathway for developing emulsified collectors for clean flotation of graphite ores, especially for reducing carbon emission.

Sedimentation of Fine Arsenopyrite with PEI and the Flotation Significance

The flotation of fine mineral particles is always a difficult problem. The flotation of fine arsenopyrite particles (−20 μm) in a sodium butyl xanthate (SBX) system was studied by using polyethyleneimine (PEI) as a flocculant. The flocculation properties of PEI on fine arsenopyrite were studied using sedimentation tests. The results showed that the optimum pH for the sedimentation of PEI was approximately 7.5; the higher the molecular weight (M.W.) of the flocculant, the better the sedimentation effect. In the flotation experiments, it was found that the flotation recovery of PEI-3 with high M.W. as flocculant was only 57%, while the flotation recovery of PEI-2 with medium M.W. was 90% under respective optimum conditions. The contact angle tests showed that the natural contact angle of arsenopyrite was 37°; the addition of moderate PEI-2 had a slightly negative influence on the hydrophobicity of arsenopyrite in the SBX system. From the size analysis results, the maximum particle size (D100) and median size (D50) of the arsenopyrite increased from 20 and 11 μm to 48 and 28 μm after treatment with 40 mg/L PEI-2, a size more conducive to bubble capture. From the combination of these results, it can be concluded that PEI-2 improved the flotation of fine arsenopyrite mainly by increasing the particle size to a suitable range through flocculation. The XPS results indicated that the adsorption of PEI-2 on the arsenopyrite surface was due to the chemisorption between the imino group and the active Fe/As sites. Applying PEI-2 to a fine disseminated arsenopyrite-type gold ore, a concentrate containing 36 g/t Au with a Au recovery of 88% can be obtained.

Uncovering the flotation performance and adsorption mechanism of a multifunctional thiocarbamate collector on malachite

In this paper, a novel collector N-octanoyl-S-carboxyethyl thiocarbamate (OCETC) containing CO, CS and -COOH groups was synthesized and applied to recover malachite. The flotation performance and adsorption mechanism of OCETC on malachite surface were systematically investigated by DFT calculation, zeta potential, FTIR, XPS, contact angle measurements and flotation experiments. It was found that CO, CS and -COOH groups were the functional sites which could react with Cu(II) ions on malachite surface and formed COCu(I) and CSCu(I) bonds. The adsorption of OCETC on malachite surface significantly improved its surface hydrophobicity since the contact angle of water on malachite changed from 46.5° to 78.0°. The flotation experiments demonstrated that 6 × 10−5 mol/L OCETC enabled the recovery of up to 98.24% malachite at pH 8.0. Under the same flotation conditions, OCETC exhibited comparable flotation recovery for malachite compared to octyl hydroxamic acid (98.43%), but much better than that by benzoyl hydroxamic acid (54.13%).

Effect of copper ions on sulfidization flotation of smithsonite: Surface properties and adsorption mechanism

This work proposed a promising method to increase the flotation recovery of smithsonite in the sulfidization xanthate system by activation with copper ions prior to addition of Na2S. The effect of copper ions on surface properties, sulfide adsorption, and floatability of smithsonite was examined using micro-flotation experiments, solution composition determination, and surface measurements. The flotation recovery of smithsonite activated by copper ions was superior to that in the direct sulfidization system, along with a maximum increase by approximately 19%. It was ascribed to an increase in active sites on smithsonite surfaces due to the formation of –O–Cu complexes. Cu2+ in the pulp solution bonded to O sites on smithsonite surfaces, and Cu(OH)+ interacted with –OH species through dehydration reaction to form activation products. It was beneficial to the interaction of sulfide species with smithsonite surfaces, and more sulfidization products formed on the mineral surface. The sulfidization products were composed of copper sulfide and zinc sulfide species in the enhanced sulfidization system, and copper sulfide species exhibited higher affinity to xanthate than zinc sulfide. It greatly improved the surface hydrophobicity of smithsonite after enhanced sulfidization with copper ions, thereby promoting the flotation recovery of smithsonite, which is significant for the sustainable production of refractory zinc oxide ores.

High-efficiency flotation of smithsonite in the presence of fine chlorite by using dispersant of sodium lignosulfonate

In the flotation process of non-ferrous metal ores, fine silicate minerals often cover the surface of the useful ores and have a serious adverse impact on the floatability of the ores. In this study, the effect of fine chlorite on the flotation behavior of smithsonite was investigated with sodium oleate (NaOL) as the collector. The micro-flotation tests showed that the flotation recovery of smithsonite was greatly affected by the chlorite, which was attributed to the slime-coating of the fine chlorite on the smithsonite surface. To eliminate the influence of chlorite on the flotation of smithsonite, sodium lignosulfonate (SLS) was introduced as a dispersant. It was found that the addition of SLS considerably improved the flotation efficiency of smithsonite. Fourier infrared spectroscopy (FT-IR) analysis, contact angle measurements and scanning electron microscope (SEM) characterization showed that SLS can adsorb on the surface of chlorite and prevent the further adsorption of NaOL so that the chlorite keeps a hydrophilic surface, avoiding the generation of hydrophobic attraction between chlorite and smithsonite and thereby attenuates or even eliminates the covering of chlorite on the smithsonite surface. Therefore, the dispersant of SLS significantly enhanced the flotation recovery of smithsonite in the presence of fine chlorite. The findings in this work indicate that the SLS as a novel dispersant might find its application in the flotation separation of nonferrous metal ores containing fine clay minerals.

Limitations of conventional sulphidisation in restoring the floatability of oxidised chalcocite

The secondary copper sulphide mineral, chalcocite, is the second most important copper mineral and its flotation is significantly affected by the surface oxidation. There is scarcity of reports on sulphidisation of oxidised chalcocite and literature suggests that the conventional sulphidisation experiences difficulties in activating sulphides that are prone to oxidation. Thus the objective of this study was to understand the sulphidisation of chalcocite, the copper sulphide most prone to surface oxidation. To achieve this, surface analysis by Cryogenic X-ray photoelectron spectroscopy, Cyclic Voltammetry measurements and flotation tests were adopted. It was found that the lower flotation recovery of the oxidised chalcocite after sulphidisation at 0.10 V vs. standard hydrogen electrode was attributed to partial sulphidisation, 36.2%, of the Cu(II) oxidation species to form the desired Cu(I)-S product, while 62.8% of the species remained unsulphidised. It was revealed that all the Cu(II) oxidation species on chalcocite were sulphidised to the desired Cu(I)-S product at the lower potential of −0.20 V. Intriguingly, the flotation recovery was even lower than that obtained at 0.10 V. The limited improvement in flotation even though the surface was fully sulphidised was attributed to the high electrochemical activity and re-oxidation of the Cu(I)-S product formed.

New insights into the impact of acid surface pretreatment on the flotation of three classified ilmenites

The effect of acid surface pretreatment on the flotation behaviors and surface properties of three classified ilmenites was studied with sodium oleate (NaOL) collector. Three ilmenites had different flotation recoveries in the range from 38% to 64% at the NaOL concentration of 1.0 × 10−4 mol·L−1. After acid surface pretreatment, their flotation recoveries all reached the maximum of over 82%, and the NaOL adsorption and the surface hydrophobicity increased to a close level. XPS analyses proved that the acid surface pretreatment changed the active sites chemisorbed with NaOL collector from Fe3+ ion to Fe3+, Fe2+, Ti4+, and Mg2+ ions on three ilmenite surfaces due to the dissolution of elements. Meanwhile, the XPS and AFM analysis results confirmed that after surface dissolution of elements, the action strengths and distribution densities of the main Fe and Ti elements with collector were enhanced on three ilmenite surfaces. Hence, their floatability all enhanced greatly.

Mechanism of manganese ion interaction with the surface of scheelite and calcite and its effect on flotation separation

Scheelite and calcite have similar surface physicochemical qualities and share the same calcium ion active sites in the mineral surface, making their separation more challenging. In this work, the effect of manganese chloride on the flotation separation of scheelite and calcite was explored utilizing flotation tests, Zeta potential tests, Fourier-transform infrared spectroscopy (FTIR), adsorption amount estimation, and X-ray Photoelectron Spectroscopy (XPS). The flotation test revealed that scheelite recovery increases gradually with increasing manganese chloride following manganese chloride addition, while the recovery of calcite gradually decreases. The recovery difference between the two minerals reached 82.84% points, achieving a better separation of scheelite and calcite. Manganese chloride produced manganese ions on the surface of scheelite, as confirmed by infrared spectroscopy, adsorption measurements, and X-ray Photoelectron Spectroscopy (XPS). Manganese ions were adsorbed on the surface of scheelite when manganese dichloride was added, increasing the number of cations on the surface and improving scheelite sodium oleate (NaOL) interaction. Furthermore, the addition of manganese ions increased the selectivity of sodium silicate, which increased its inhibition on the calcite surface, reducing sodium oleate adsorption on the calcite surface and thus reducing flotation recovery, achieving the goal of separating the two minerals.

Strengthening the flotation recovery of silver using a special ceramic-medium stirred mill

Strengthening the flotation recovery of silver by fine grinding with special ceramic-medium stirred mill (SCSM), steel ball-medium stirred mill (SBSM) and ball mill (BM) were investigated, respectively. Grinding with SCSM exhibited better performance in terms of Ag recovery, which was approximately 2% higher than those obtained by grinding with SBSM and BM. The reduction of iron ions produced during grinding with SCSM was conducive to the recovery of silver minerals. Additionally, it was found that high liberation degree of silver minerals from gangue minerals was achieved by grinding with SCSM, and this is mainly attributable to good flow characteristics of ceramic medium. The liberation degree of silver minerals in the grinding products was as high as 77.33% after using SCSM to grind the ore to 85% passing 74 μm, suggesting that most silver minerals in the ore have been liberated. The Ag content and Ag recovery of the silver concentrates were basically the same in the cases of grinding with SBSM and BM. SCSM showed considerable potential in fine grinding of non-ferrous and noble metal ores.

Efficacy of sustainable polymers to mitigate the negative effects of anisotropic clay minerals in flotation and dewatering operations

The depletion of high-grade ore resources and ongoing demand for mineral products has led to an increase in the exploitation of low-grade and complex ores, which often contain colloid clay particles (e.g., kaolinite) that are detrimental to flotation and dewatering unit operations in mineral processing. During flotation, clay particles increase the pulp viscosity and produce a slime coating by adsorption on the surface of valuable minerals resulting in the reduction of the flotation grade and recovery. Clay particles are also suspended in mine tailings that can cause dewatering challenges in flocculation operations. The clay mitigation strategies employed during flotation (dilution and use of dispersants) and dewatering (addition of flocculants) involve reagents from non-renewable sources that can have deleterious consequences on the environment and aquatic biota. As part of an effort to find environmentally benign reagents, we evaluated the performance of six sustainable polymers (protein- and polysaccharide-based biopolymers) for their potential as dispersants and flocculants of kaolinite clay particles. Their effectiveness was assessed via chalcopyrite froth flotation, settling, and turbidity tests. Zeta potential, adsorption isotherm by total organic carbon, and X-ray scattering tests were also conducted to understand the interactions between biopolymers and kaolinite mineral surfaces. At pH 7 and 10, the anionic polysaccharide pectin showed promising dispersant efficiency in flotation and the cationic protein protamine significantly improved kaolinite flocculation in dewatering operation. Outcomes of this investigation demonstrate that commercially available sustainable polymers or “biopolymers” have a significant potential to use to mitigate the negative effects of clay particles in minerals processing to reduce environmental issues arising from inorganic and synthetic organic reagents from non-renewable sources.

Effect of TIPA/TEA combined grinding aid on the behavior of quartz flotation in DDA system

In this paper, different dosages of TIPA, TEA and their combined grinding aid were added to the process of quartz grinding and their influence on the grinding efficiency and flotation recovery in DDA system was investigated. From the grinding and flotation experiments, It can be known that the effect of the combined grinding aid was better than that of a single reagent, which can not only significantly improve the grinding efficiency of quartz, but also increase the recovery of quartz from flotation. Based on the results of FT-IR spectroscopy, XPS analysis, quantum chemistry and solution chemistry calculations, it can be seen that the hydroxyl groups in the TIPA/TEA combined grinding aid formed hydrogen bonds with O on the (101) surface of quartz, while collector DDA was mainly electrostatically adsorbed on the surface of quartz with negative potential, and the introduction of combined grinding aid improved the adsorption of DDA, the grinding aid and collector played a synergistic role instead of competitive adsorption. The detection of contact angle and surface tension showed that the combined grinding aid can improve the hydrophobicity of quartz, reduce the surface tension and CMC value of DDA, and enhance the dispersibility of quartz, therefore, it can increase the recovery of quartz from flotation.

Comparison of the Effects of Sodium Oleate and Benzohydroxamic Acid on Fine Scheelite and Cassiterite Hydrophobic Flocculation

Sodium oleate (NaOL) and benzohydroxamic acid (BHA) are commonly used scheelite and cassiterite flotation collectors. Hydrophobic flocculation flotation of fine minerals has been extensively studied and reported under a NaOL system, but not under a BHA system. In this paper, the particle size distribution and flotation behaviour of fine scheelite (−10 μm) and cassiterite (−37 + 10 and −23 μm) after shear stirring in NaOL, BHA, and Pb2+ + BHA systems were studied by laser particle size analysis and flotation tests. The measured particle size distribution results revealed that the fine minerals could aggregate under a NaOL system, and the aggregate size increased with increasing stirring time and speed, with scheelite aggregating faster than cassiterite. BHA did not cause scheelite or cassiterite to form hydrophobic aggregates. At low stirrer speeds, the minerals could form small, weak, and easily broken aggregates when Pb2+ + BHA was added. The results of the flotation tests revealed that increasing the stirring time and speed increased the flotation rate and recovery when NaOL and BHA were added. When Pb2+ + BHA was added, however, the changes in flotation rate and recovery were not noticeable when the stirring conditions were changed.

Molecular Dynamics Simulation Study on the Interactions of Mixed Cationic/Anionic Collectors on Muscovite (001) Surface in Aqueous Solution.

In this study, the adsorption mechanisms of dodecylamine hydrochloride(DDAHC), sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate(SDBS), and their mixed anionic/cationic collectors at ten different molar ratios on a muscovite (Mcv) surface in neutral aqueous solution were assessed by molecular dynamics simulations (MDS). According to the snapshot, interaction energy, radial distribution function (RDF), and density profile between the Mcv surface and collector molecules, the individual DDAHC collector was an effective collector for the flotation of Mcv. The molar ratio of anionic/cationic collectors was determined to be an essential factor in the flotation recovery of Mcv. The DDAHC collector was involved in the adsorption of the mixed anionic/cationic collectors on the Mcv (001) surface, whereas SDS and SDBS collectors were co-adsorbed with DDAHC. The mixed cationic/anionic collector showed the best adsorption on the Mcv surface in a molar ratio of 2. Additionally, SDBS, which has one more benzene ring than SDS, was more likely to form spherical micelles with DDAHC, thus resulting in better adsorption on the Mcv surface. The results of micro-flotation experiments indicated that the DDAHC collector could improve the flotation recovery of Mcv in neutral aqueous solution, which was in agreement with MDS-derived findings. In conclusion, DDAHC alone is the optimum collector for Mcv flotation under the neutral aqueous conditions, while the mixture of DDAHC and SDBS collectors (molar ratio = 2:1) exhibits the similar flotation performance.

The effect of high voltage electrical pulses on iron ore comminution to improve desulfurization flotation recovery

The effect of high voltage electrical pulses on iron ore comminution to improve desulfurization flotation recovery

Prediction of grade and recovery in flotation from physicochemical and operational aspects using machine learning models

Machine learning (ML) models for predicting flotation behavior focus on operational variables. Fundamental aspects, e.g., physicochemical variables that describe mineral surfaces for bubble–particle interactions, are largely neglected in these models; however, these physicochemical variables of mineral particles, including bubbles and pulp, influence the flotation behavior. Thus, this study aimed to advance the prediction of flotation behavior by including physicochemical variables. Among four ML models used for the prediction, the random forest model had the best performance and was therefore subsequently used to investigate variable importance. Contact angle, particle diameter, bubble diameter, particle charge, collector concentration, flotation time, and number of mineral species were the most important variables. Limitations (e.g., assumptions and empiricism) and implications of our study were presented. Finally, our expectation was to encourage more attention to physicochemistry in flotation using ML for a more generalized empirical flotation model.

Simulation of bubble–particle attachment process and estimation of attachment probability using a coupled smoothed particle hydrodynamics–discrete element method model

The bubble–particle attachment is an important step in determining the success of recovery in froth flotation. In this study, the bubble–particle attachment process was investigated using a coupled smoothed particle hydrodynamics (SPH)–discrete element method (DEM) model. The effects of particle inertia and the drag of fluid flow on the particle motion were examined. The sliding time was determined for different particle sizes, densities, and bubble sizes, and the simulated sliding time was compared with the analytical solution and our own experimental results using a high-speed camera. As the particle size and density increased, the sliding time decreased. However, this value was independent of the bubble size. The induction time was calculated as a function of the particle size and contact angle from an empirical model, and it was used to determine the attachment and net probabilities in a dynamic simulation. Based on the SPH–DEM simulation results, novel probability models were developed for bubble–particle interactions. Both attachment and net probabilities could be decoupled into hydrodynamic and thermodynamic effects, given that the collision probability was also derived as a single function of the particle Stokes number. The developed probability models embodying the mutual influence of bubbles and particles can be extended to macroscopically describe flotation cells and evaluate cell performance including particle recovery.