Flotation Collector Research Articles

Synthesis and characterization of hydroxamic acid N,3-dihydroxy-2-naphthamide and its copper (II) complex per keto/enol forms and rare earth flotation

Flotation is the most common beneficiation process used for separating minerals, but for rare earth minerals (REMs), performance can suffer due to the dilute nature of the rare earth elements. Furthermore, the REMs tend to possess smaller grain sizes, making the use of traditional flotation cells difficult if total liberation is needed. Consequently, improved efficiencies are needed for extracting REMs from various sources. For these systems, hydroxamic acids are commonly used as flotation collectors. Two such hydroxamic collectors were studied in this work: salicylhydroxamic acid (SHA) and N,3-dihydroxy-2-naphthamide (H2O5). Because there is no documented synthesis route for H2O5, several synthesis approaches were examined. Furthermore, because there is no information on H2O5, important structural and characteristic data was gathered regarding its (1) preferred structural isomer as a Cu2+ complex and (2) electrostatic potential values of the possible dentate groups in different tautomeric forms, thereby allowing H2O5 to be compared to SHA, particularly regarding flotation behavior. Hydrogen nuclear magnetic resonance (H-NMR), Laser Raman Spectroscopy (LRS), and predominantly Fourier-Transform Infrared (FT-IR) spectroscopy showed that both SHA and H2O5 preferred to be keto tautomers when uncomplexed; however, once chelated to Cu2+ ions, the collectors adopted enol forms. Molecular modeling using Spartan software showed an increase in the electrostatic potential of the possible dentate groups in both molecules for the enol form. H2O5 also resulted in an increased recovery by flotation of REMs of about 23% compared to SHA at similar reagent dosages.

Adsorption of salicyl hydroxamic acid and octyl hydroxamic acid mixture on the cassiterite minerals

Salicylhydroxamic acid (SHA) and octyl hydroxamic acid (OHA) are two commonly used hydroxamic acid-based collectors in fine cassiterite flotation. While some reports suggest that a mixture of OHA and SHA yields superior results compared to their individual use, there is a lack of experimental exploration and theoretical analysis. In this study, the flotation performance and the associated adsorption mechanism of SHA, OHA and their mixture on fine cassiterite particles was systematically investigated. The results demonstrate a synergistic effect between SHA and OHA in enhancing fine cassiterite flotation, with the most significant enhancement occurring at a 1:1 mass ratio under the natural pH conditions. This finding is corroborated by contact angle and zeta potential tests. When both SHA and OHA are present, SHA likely attaches to the cassiterite surface via chemisorption in the form of a five-membered chelate ring, while OHA adheres through physical adsorption, primarily establishing hydrogen bonds with oxygen sites on the cassiterite surface or with SHA molecules. The adsorption ratio of SHA to OHA onto cassiterite surfaces is approximately 69%: 31% when an equal mass of SHA and OHA interact with cassiterite under the natural pH condition.

Thiourea compounds with diverse hydrophobic group used as selective flotation collectors for galena

Hydrophobic group is a crucial yet underutilized component of a collector molecule. Herein we examine the flotation behaviors of thioureas with various hydrophobic groups for a galena/sphalerite mixed flotation system and compare them with sodium ethyl-xanthate (SEXT). Flotation experiments show that thiourea collectors with shorter alkyl chain and less nucleophilic amine nitrogen display better separation performance. Larger contact angles and adsorption capacities between the thiourea collectors and galena are the key to the enhanced selectivity.In the homogeneous Zn2+/Pb2+ mixed solution, thiourea collectors exhibit strong coordination ability with Pb2+, and their selectivities are noticeably higher than that of SEXT. FTIR and single crystal X-ray diffraction studies prove that thiourea collectors coordinate with metal ions through the S atom only. DFT calculations reveal how side-chain size and type can affect the selectivity.

Recycle of Pb-BHA collectors based on the adsorption and desorption mechanism on scheelite surface

Tungsten, as an important strategic mineral resource, has significant importance for the economic and social development of our country. In recent years, the application of the lead complex of benzohydroxamic acid (Pb-BHA) as a collector in tungsten flotation has greatly facilitated the efficient and clean separation of complex scheelite resources. However, the residual Pb-BHA agents on the surface of scheelite concentrate not only severely hinder subsequent the hydrometallurgical processes but also result in substantial wastage of collectors. Based on the adsorption configuration of the Pb-BHA complex on the scheelite surface, this study conducted experimental research on the desorption and reuse of residual Pb and BHA. The experimental results demonstrate that alkaline treatment can effectively desorb over 90% of Pb and BHA, effectively addressing the foam issues encountered during hydrometallurgical process. Furthermore, the recycling of desorption solution to the original tungsten flotation process in actual ores could significantly decrease the dosage of Pb-BHA by 25% without compromising the concentrate grade, achieving the effective recycling of Pb-BHA on the surface of scheelite concentrate.

Performance Comparison of Waste Cooking Oil on Coal Slime Flotation with Sunflower Oil and Gas Oil

This study explores the potential use of waste cooking sunflower oil (WSO) as an eco-friendly collector for coal slime flotation. WSO and coal slime are both wastes and are hazardous to human health and the environment, if not disposed of properly. In this study, co-disposal of the two wastes was investigated; a gas oil (petroleum derived oil) and crude sunflower oil (CSO) were used for collector efficiency comparisons. This study also presents a green, low-cost and environmentally friendly alternative. Kinetic flotation tests were carried out to study the flotation selectivity, flammability and combustible recovery. Contact angle measurements were performed with 3 different oils (CSO, WSO and gas oil) by sessile drop technique to determine the hydrophobicity and surface properties of coal. Fourier-transform infrared (FTIR) spectroscopy was utilized to analyze the chemical composition of both waste oil and coal samples. 
 Keywords: Sunflower oil, waste cooking oil, gas oil, coal slime, flotation

An insight into fine cassiterite recovery: A novel surfactant-phenylpropylhydroxamic acid and its adsorption mechanism

The effective recovery of fine-grained cassiterite is a difficult problem in tin ore beneficiation. For enhancing the performance of the traditional collector for fine cassiterite flotation, a novel surfactant phenyl propyl hydroxamic acid (PHA) was designed by introducing one ethyl group (–CH2-CH2-) into benzohydroxamic acid (BHA).The study of flotation properties and the adsorption mechanism of PHA onto cassiterite surface were systematically investigated by scanning electron microscopy-energy dispersive X-ray spectroscopy testing (SEM-EDS), adsorption measurements, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Density functional theory (DFT). The results indicate that PHA has an excellent flotation performance for fine cassiterite compared with BHA and salicylhydroxamic acid (SHA), and the interaction between PHA and the surface of mineral mainly exhibited chemisorption attributed to new Sn-O chemical bonds. Meanwhile, DFT calculations showed that PHA adsorbed on the cassiterite surface via chelating interaction by the formation of a five-membered chelate ring.

Selective Separation Behavior and Study on the Interaction Mechanism of 2-Hydroxy-3-Naphthylmethyl Hydroxamic Acid and Cassiterite

In this study, the performance of 2-hydroxy-3-naphthylmethyl hydroxamic acid (NHA) in cassiterite flotation was investigated. The aim was to understand the mechanism of action of NHA for the first time. The effect of NHA as a collector in the flotation separation of cassiterite, calcite, and quartz was investigated via microbubble flotation experiments. The experimental results showed that the maximum recovery of cassiterite in the presence of NHA was 91.76%. This was attributed to the selective adsorption of NHA on the cassiterite surface. NHA showed a stronger collection performance for cassiterite than calcite and quartz. Therefore, the mechanism of NHA-cassiterite interaction was investigated using zeta potential, the logarithmic solubility plot (LSD), Fourier Transform Infrared (FT-IR), X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscope (SEM) analyses. This study introduces a new adsorption process and mechanism for the NHA-based adsorption of cassiterite. The results show that, under neutral conditions, the solute components of cassiterite surface lattice ions mainly exist in the form of Sn–OH complexes. Chemisorption occurs between cassiterite and NHA which is adsorbed onto the cassiterite surfaces through interaction with O sites, rather than Sn sites as is traditionally expected. Further, the hydroxyl and hydroxyl groups of NHA are chemically coordinated with Sn–OH on the surface of cassiterite to form a six-membered chelate ring. This proposed mechanism can be extended to most systems in which metal ions interact with hydroxamic acids bearing hydroxyl groups. This contributes to a better understanding of the activation mechanism of hydroxamic acid collectors in cassiterite flotation.

Synthesis and application of dithiocarbamate oxadiazole thione for flotation separation of malachite from quartz and calcite

In this paper, 5-methyl hexyldithiocarbamate-1,3,4-oxadiazole-2-thione (MHCODT) was synthesized for the first time and introduced as a flotation collector in malachite flotation separation process from quartz and calcite. During the micro-flotation experiment, it was found that MHCODT showed stronger flotation ability and selectivity for malachite than conventional collector octyl hydroxamic acid (OHA), and achieved effective separation and enrichment of malachite. Measurements of contact angles, ζ-potentials and UV spectra demonstrated that MHCODT specifically adhered to the surface of malachite rather than quartz and calcite. Then, FTIR and X-ray photoelectron spectroscopy (XPS) demonstrated that Cu of malachite surface combined with S and N of MHCODT to form MHCODT-Cu(I) complexes, accompanied by the reduction of divalent Cu. The result of density functional theory (DFT) method indicated that the CS bonds and NH bonds in oxadiazole thione and the dithiocarbamate groups were the chemical reaction center. Based on the above test results, the adsorption models of MHCODT-Cu+ and MHCODT-Cu2+ were proposed.

Efficient adsorption of butyl xanthate by imidazolium ionic liquid modified fumed silica

Butyl xanthate (BX) usually serve as an available collector in the sulfide mineral flotation. However, it will cause severe pollution and be harmful for living beings when discharged together with beneficiation wastewater. Adsorption, affected by sorbents structure to a great extent, is an effective strategy to treat BX-bearing wastewater. In this paper, ionic liquid-loaded fumed silica (IFS) generated by a simple process was acted as an adsorbent for removing BX from aqueous solution. The ratio of IL loaded onto silicon was about 40 %. The N elements existing in the structure of adsorbents suggested IL loaded onto silica surface successfully. The specific surface area of IFS was 65.25 m2/g, which was smaller than original material. And the total pore volume decreased from 36.75 to 15.22 cm3 g−1 after modification. Different from the virginal silica barely adsorbing BX, ionic liquid (IL) loaded silica had large uptake capacity up to 202.84 mg/g under the combined effect of functional groups modified in the silica particle and the porous structure of nanomaterial. The adsorption kinetics and isotherms are followed with the pseudo-second-order model and Langmuir model, respectively. And the functional groups, charge of adsorbent were analyzed to reveal approaching mechanism. This paper provides an alternative for xanthate and other organic contaminants treatment.

Exploring the potential of the halotolerant bacterial strain Bacillus subtilis LN8B as an ecofriendly sulfide collector for seawater flotation.

To assess the effectiveness of Bacillus subtilis strain LN8B as a biocollector for recovering pyrite (Py) and chalcopyrite (CPy) in both seawater (Sw) and deionized water (Dw), and to explore the underlying adhesion mechanism in these bioflotation experiments. The bioflotation test utilized B. subtilis strain LN8B as the biocollector through microflotation experiments. Additionally, frother methyl isobutyl carbinol (MIBC) and conventional collector potassium amyl xanthate (PAX) were introduced in some experiments. The zeta potential (ZP) and Fourier-transform infrared spectroscopy (FTIR) was employed to explore the adhesion mechanism of Py and CPy interacting with the biocollector in Sw and Dw. The adaptability of the B. subtilis strain to different water types and salinities was assessed through growth curves measuring optical density. Finally, antibiotic susceptibility tests were conducted to evaluate potential risks of the biocollector. Superior outcomes were observed in Sw where Py and CPy recovery was ∼39.3%±7.7% and 41.1%±5.8%, respectively, without microorganisms' presence. However, B. subtilis LN8B potentiate Py and CPy recovery, reaching 72.8%±4.9% and 84.6%±1.5%, respectively. When MIBC was added, only the Py recovery was improved (89.4%±3.6%), depicting an adverse effect for CPy (81.8%±1.1%). ZP measurements indicated increased mineral surface hydrophobicity when Py and CPy interacted with the biocollector in both Sw and Dw. FTIR revealed the presence of protein-related amide peaks, highlighting the hydrophobic nature of the bacterium. The adaptability of this strain to diverse water types and salinities was assessed, demonstrating remarkable growth versatility. Antibiotic susceptibility tests indicated that B. subtilis LN8B was susceptible to 23 of the 25 antibiotics examined, suggesting it poses minimal environmental risks. The study substantiates the biotechnological promise of B. subtilis strain LN8B as an efficient sulfide collector for promoting cleaner mineral production. This effectiveness is attributed to its ability to induce mineral surface hydrophobicity, a result of the distinct characteristics of proteins within its cell wall.

Study on quantitative structure–activity relationship of amine surfactants in coal reverse flotation

AbstractWith the deterioration of underground coal quality, hundreds of millions of tons of coal slime in China need to be treated using flotation methods every year. However, the design and selection of coal slurry flotation collectors lack theoretical guidance. In this paper, the quantitative structure–activity relationship (QSAR) model between the molecular structure descriptors of collectors and the flotation recovery and selectivity index is established by using pure kaolinite/clean coal flotation experiments and molecular simulation techniques. Flotation results showed that the flotation recovery rate of kaolinite by collectors with larger head group size, such as DDMAC, DDP, and DTAC, is higher than that of the other collectors with smaller head group size. DDA, DDP, and DD have similar flotation capabilities for clean coal, and their selectivity was slightly better than others. The QSAR model between the molecular structure descriptor and the selectivity index was successfully constructed by combining flotation experiments and molecular simulation results. The reliability of this model has been proven through theoretical analysis and flotation experiments. The molecular simulation results indicate that all eight collectors can advertise on 001 (−) surface of kaolinite, but the final advertisement configuration is different. DDA has less coverage on the surface of kaolinite. When the collector is DDA, the concentration of water molecules near the 001 (−) surface of kaolinite is the highest, indicating that the collector DDA has the weakest effect on improving the hydrophobicity of the 001 (−) surface of kaolinite. DDMAC and DDBAC have the best facilitation to the surface hydrophobicity of kaolinite 001 (−). The research results have theoretical guidance significance for the selection and design of mineral flotation collectors.

A review of the application of nanoparticles as collectors in ion flotation

Ion flotation is one of the most promising and unique methods for reducing or removing toxic heavy metal ions, organic pollutants, or inorganic anions and cations from mining and metallurgical wastewaters. It is a cost-effective and convenient method. In ion flotation, surface-active ions are removed from aqueous solutions by adding surfactants. Therefore, the main purpose of this review article was to summarize the application of various surfactants (nanoparticle surfactants, chemical synthetic surfactants and biosurfactants) used in ion flotation. Then, the advantages, disadvantages, and prospects of surfactants were comprehensively discussed. Recent progress regarding nanoparticle surfactants in ion flotation and the mechanism of colligends binding with nanoparticles were evaluated.

A novel sodium trans-2-nonene hydroxamate for the flotation separation of ilmenite and forsterite: Superior collecting and selectivity

Sodium trans-2-nonene hydroxamate (NaTNA), a derivative of hydroxamic acid, was successfully synthesized as an effective collector for the flotation separation of ilmenite and forsterite. Micro-flotation results showed that NaTNA exhibits a superior flotation performance for ilmenite compared to sodium oleate. To elucidate the flotation process, the zeta potential, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used to analyze the interaction between the reagents and mineral surfaces. The results indicated that NaTNA was strongly adsorbed on the ilmenite (Ti and Fe active sites) surface by chelation but weakly adsorbed on the forsterite surface through electrostatic attraction. Quartz crystal microbalance with dissipation results suggested that a slim NaTNA layer with an adsorption density of 112.50 ng/cm2 was detected on the forsterite surface, whereas a significantly thicker NaTNA layer with an adsorption density of 4415.00 ng/cm2 was detected on ilmenite. Moreover, a molecular dynamics simulation was employed to investigate the adsorption mechanism of NaTNA on ilmenite and forsterite, revealing that the O‐O distance (2.746 Å) in TiO42- sufficiently matched with the O‐O distance (2.723 Å) of NaTNA. This facilitated bond formation between the reagents and ilmenite. Overall, NaTNA is a promising collector for ilmenite flotation, exhibiting excellent collection ability and selectivity.

Quantitative evaluation of collector flotation performance II: The creation of a collector property index based on molecular structure

The evaluation and prediction of flotation performance is a key step in the development of high-performance collectors for the efficient flotation separation of low-grade complex ores. In our previous work, we have created the flotation index (FI) for a comprehensive and standardized evaluation of collector flotation performance. However, as an experiment-based index, FI does not possess the quantitative predictive power that is fundamental to rational flotation reagent design. In this work, the collector properties were obtained by quantum chemistry (QC) calculation. By ranking the importance of the QC properties, machine learning (ML) aids the selection of key properties representing different aspects of a collector (polar, non-polar and overall polarity). The key properties were incorporated into a theory-based collector property index (CPI). Based on a quantitative structure–activity relationship (QSAR), the bridge between theory and experiment were established by searching for the relationship CPI and FI, enabling convenient evaluation and prediction of collector flotation performance. The accuracy of our QSAR model was verified using the galena-pyrite separation system. Our QSAR model demonstrates transferability in that it can predict collectors with diverse skeletons or types, pushing the limit of most conventional QSAR models, which only apply to collectors with similar skeletons or types. This work provides an alternative pathway for the rational design and performance prediction of flotation surfactants.

Interaction mechanisms of typical collectors with zircon surfaces and their influence on surface morphology and hydrophobicity for selective flotation

Zircon is the primary mineral that contains the critical metals zirconium and hafnium. However, the extraction of pure zircon from its natural ore is challenging. The inadequate understanding of the interaction mechanisms between traditional flotation collectors, namely n-octyl phosphonic acid (nOPA), octyl-hydroxamic acids (OHA), and oleic acid (OL), with zircon, has hindered the development of highly selective flotation reagents. Therefore, a combination of atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), Zeta potential tests, contact angle measurements, and flotation tests was employed to elucidate the mechanism of collector adsorption on surface morphology and the chemical bonding interactions at the interface. The AFM, XPS, and DRIFTS results consistently demonstrate that all three reagents can chemically bond with zircon surfaces. nOPA exhibits stronger interactions with zircon compared to OL and OHA, as it coordinates with two zirconium sites to form a monolayer. Zeta potential and contact angle measurements reveal that the surface morphology and weak adsorption, which is driven by weak interactions, contribute to an improvement in hydrophobicity. Flotation results further validate that the three reagents can selectively float zircon in specific pH ranges. The interfacial bonding interactions, which are influenced by weak interactions, play significant roles in the flotation of zircon.

A quantitative innovation perspective on synergism and selectivity mechanism of mixed collectors in flotation

Use of mixed collectors in froth flotation confirmed effective separation of minerals with better selectivity and synergistic effects. But the underlying interaction mechanism still keep vague and have not been interpreted clearly so far. This work proposed a quantitative perspective to account for experimental flotation behavior from active site calculation, which has not been involved in flotation areas yet. Specifically, the mineral site distributions of diaspore and kaolinite were quantitatively characterized through calculated collector (sodium oleate (NaOL) and benzohydroxamic acid (BHA)) adsorption intrinsic constants. The algorithm principle was radically different from common homogeneous solution system without electric double layer. Using collector adsorption constants, all the initial and adsorbed product sites were counted in any circumstances to compare with corresponding flotation tests. The results showed that the 5 % higher recovery of diaspore at NaOL/BHA = 9:1 was attributed with 2 % more adsorption sites occupied than a single NaOL when both doses were controlled at 5 × 10-4 mol/L. On the contrary for kaolinite, the overall coverage of collectors was much smaller, indicating its poor recovery. Despite 10 % NaOL replacement by BHA in mixed collectors, neither the adsorbed site content nor the flotation efficiency for kaolinite was facilitated finally. Therefore, the significant discrepancies in adsorptions and flotations between diaspore and kaolinite contribute to their separation with the better selectivity of mixed NaOL/BHA than individual NaOL. The method established in this study may draw further attention for complex collector adsorption to facilitate flotation development.

Investigation on the preparation of coal slime flotation microemulsion collector: A combination of experimental and simulation method

Microemulsion collector is a new type of highly efficient collector for coal slime flotation, but the research on their formulation is complexity and time-consuming, which restricts the development and application of the collector. In this work, an efficient method was designed for preparing microemulsion collectors through combined experiments and simulation. The dissipative particle dynamics simulation studies showed that CPE-12 was the surfactant for the preparation of microemulsion collector, and n-pentanol was the cosurfactant. And the Km value range was between 1.0 and 1.5. The experimental studies based on simulation showed that the Km value was 1.2 and the content of water was greater than 20%. The composition of the microemulsion collector was 22.91% CPE-12, 19.09% n-pentanol, 28.00% n-dodecane, and 30.00% water. The centrifugation and short-term storage experiments showed HB-MC has good stability for daily storage and transportation. The flotation test studies showed that, under the condition of similar ash content of clean coal, the yield of clean coal floated by the HB-MC was 1.42% higher than that of n-dodecane, and its dosage was 18.18% of that of n-dodecane. Moreover, the flotation of long flame coal slime using HB-MC without adding frother.

Study on the flotation mechanism of cobalt-bearing pyrite: A DFT calculation

The adsorption mechanism of flotation collector methyl xanthate on the pure and Co-doped FeS2 (100) crystal plane was investigated by density functional theory (DFT) calculation. For the purpose of comprehensive calculation, the top sites on the two nearest neighbor Fe atoms (TFe-Fe-I) of the FeS2 (100) crystal plane, and on the one Co atom and one nearest neighbor Fe (TFe-Co) as well as on the top sites on the two nearest neighbor Fe atoms (TFe-Fe-II) of the Co-doped FeS2 (100) crystal plane are taken into account, respectively. The adsorption energy analysis showed that the TFe-Co sites on the Co-doped FeS2 (100) crystal plane were more favorable for methyl xanthate adsorption. Furthermore, From the charge density difference and Bader charge analysis results of the most stable adsorption configuration of methyl xanthate on TFe-Co sites of the Co-doped FeS2 (100) crystal plane, it can be clearly seen that the direction of charge transfer is S to Fe and Co after methyl xanthate adsorption on mineral surfaces. The results of projected density of states (PDOS) and crystal orbital Hamilton population (COHP) in terms of the complex interactions atomic orbitals and chemical bonds further reveal that Co substitution of Fe in FeS2 promoted the adsorption of methyl xanthate onto the Co-doped FeS2 (100) surface.

N-[6-(hydroxyamino)-6-oxohexyl]octanamide: A collector derived from the structure of octyl hydroxamic acid and its application in bastnaesite flotation

Bastnaesite has always been faced significant challenges in its flotation separation from its associated gangue minerals like fluorite. Despite being a commonly employed collector for oxide mineral flotations, octyl hydroxamic acid (OHA) still exhibits insufficient selectivity. Consequently, a novel hydroxamic acid, N-[6-(hydroxyamino)-6-oxohexyl]octanamide (NHOO), is synthesized and employed as a collector in bastnaesite flotation, building upon the structure of OHA. Flotation experiments under neutral conditions demonstrate the effective ability of NHOO to achieve a difference of nearly 60% in the recoveries between bastnaesite and fluorite during their separation. Concordant outcomes from zeta potential characterizations, adsorption tests, and X-ray photoemission spectroscopy validate heightened adsorption quantities of NHOO on bastnaesite surface relative to fluorite under identical dosage conditions. Ab initio calculations unveil the capability of NHOO to establish a pentacoordinate chelate ring on bastnaesite surface, whereas on fluorite, it can only form a singular chemical bond. Consequently, NHOO shows a considerably lower energy associated with its adsorption on bastnaesite surface in comparison to its energy on fluorite surface.

Effect of ultrasonic treatment on physicochemical characteristics of flotation collectors used in sylvinite ore desliming

Effect of ultrasonic treatment on physicochemical characteristics of flotation collectors used in sylvinite ore desliming