Alkyl dimethyl betaine activates the low-temperature collection capacity of sodium oleate for scheelite

The impact of alkyl dimethyl betaine (ADB) on the collection capacity of sodium oleate (NaOl) at low temperatures was evaluated using flotation tests at various scales. The low-temperature synergistic mechanism of ADB and NaOl was explored by infrared spectroscopy, X-ray photoelectron spectroscopy, surface tension measurement, foam performance test, and flotation reagent size measurement.The flotation tests revealed that the collector mixed with octadecyl dimethyl betaine (ODB) and NaOl in a mass ratio of 4:96 exhibited the highest collection capacity. The combined collector could increase the scheelite recovery by 3.48% at low temperatures of 8–12℃. This is particularly relevant in the Luanchuan area, which has the largest scheelite concentrate output in China. The results confirmed that ODB enhanced the collection capability of NaOl by improving the dispersion and foaming performance. Betaine can be introduced as an additive to NaOl to improve the recovery of scheelite at low temperatures.

Flotation separation of scheelite from calcite using luteolin as a novel depressant

This paper proposes luteolin(LUT)as a novel depressant for the flotation-based separation of scheelite and calcite in a sodium oleate(NaOL)system.The suitability of LUT as a calcite depressant is confirmed through micro-flotation testing.At pH=9,with LUT concentration of 50 mg·L^(-1) and NaOL concentration of 50 mg·L^(-1),scheelite recovery reaches 80.3%.Calcite,on the other hand,exhibits a recovery rate of 17.6%,indicating a significant difference in floatability between the two minerals.Subsequently,the surface modifica-tions of scheelite and calcite following LUT treatment are characterized using adsorption capacity testing,Zeta potential analysis,Fourier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS),and atomic force microscopy(AFM).The study in-vestigates the selective depressant mechanism of LUT on calcite.Adsorption capacity testing and Zeta potential analysis demonstrate sub-stantial absorption of LUT on the surface of calcite,impeding the further adsorption of sodium oleate,while its impact on scheelite is min-imal.FT-IR and XPS analyses reveal the selective adsorption of LUT onto the surface of calcite,forming strong chemisorption bonds between the hydroxyl group and calcium ions present.AFM directly illustrates the distinct adsorption densities of LUT on the two miner-al types.Consequently,LUT can effectively serve as a depressant for calcite,enabling the successful separation of scheelite and calcite.

Efficient desorption and reuse of collector from the flotation concentrate:A case study of scheelite

Flotation is the most common method to obtain concentrate through the selective adsorption of collectors on target minerals to make them hydrophobic and floatable.In the hydrometallurgy of concentrate,collectors adsorbed on concentrate can damage ion-exchange resin and increase the chemical oxygen demand(COD)value of wastewater.In this work,we proposed a new scheme,i.e.,desorbing the collectors from concentrate in ore dressing plant and reusing them in flotation flowsheet.Lead nitrate and benzohydroxamic acid(Pb-BHA)complex is a common collector in scheelite flotation.In this study,different physical(stirring or ultrasonic waves)and chemical(strong acid or alkali environment)methods for facilitating the desorption of Pb-BHA collector from scheelite concentrate were explored.Single-mineral desorption tests showed that under the condition of pulp pH 13 and ultrasonic treatment for 15 min,the highest desorption rates of Pb and BHA from the scheelite concentrate were 90.48%and 63.75%,respectively.Run-of-mine ore flotation tests revealed that the reuse of desorbed Pb and BHA reduced the collector dosage by 30%for BHA and 25%for Pb.The strong alkali environment broke the chemical bonds between Pb and BHA.The cavitation effect of ultrasonic waves effectively reduced the interaction intensity between Pb-BHA collector and scheelite surfaces.This method combining ultrasonic waves and strong alkali environment can effectively desorb the collectors from concentrate and provide“clean”scheelite concentrate for metallurgic plants;the reuse of desorbed collector in flotation flowsheet can reduce reagent cost for ore dressing plants.

Texture and Geochemistry of Multi-stage Hydrothermal Scheelite in the Mamupu Cu-Au-Mo(-W)Deposit,Eastern Tibet:Implications for Tungsten Mineralization in the Yulong Belt

Multistage tungsten mineralization was recently discovered in the Mamupu copper-polymetallic deposit in the southern Yulong porphyry copper belt(YPCB),Tibet.This study reports the results of cathodoluminescence,trace element and Sr isotope analyses of Mamupu scheelite samples,undertaken in order to better constrain the mechanism of W mineralization and the sources of the ore-forming fluids.Three different types of scheelite are identified in the Mamupu deposit:scheelite A(Sch A)mainly occurs in breccias during the prograde stage,scheelite B(Sch B)forms in the chlorite-epidote alteration zone in the retrograde stage,while scheelite C(Sch C)occurs in distal quartz sulfide veins.The extremely high Mo content and negative Eu anomaly in Sch A represent high oxygen fugacity in the prograde stage.Compared with ore-related porphyries,Sch A has a similar REE pattern,but with higher ΣREE,more depleted HREE and slightly lower(^(87)Sr/^(86)Sr)i ratios.These features suggest that Sch A is genetically related to ore-related porphyries,but extensive interaction with carbonate surrounding rocks affects the final REE and Sr isotopic composition.Sch B shows dark(Sch B-I)and light(Sch B-II)domains under CL imaging.From Sch B-I to Sch B-II,LREEs are gradually depleted,with MREEs being gradually enriched.Sch C has the highest LREE/HREE ratio,which indicates that it inherited the geochemical characteristics of fluids after the precipitation of HREE-rich minerals,such as diopside and garnet,in the early prograde stage.The Mo content in Sch B and Sch C gradually decreased,indicating that the oxygen fugacity of the fluids changed from oxidative in the early stages to reductive in the later,the turbulent Eu anomaly in Sch B and Sch C indicating that the Eu anomaly in the Mamupu scheelite is not solely controlled by oxygen fugacity.The extensive interaction of magmatic-hydrothermal fluids and carbonate provides the necessary Ca^(2+)for the precipitation of scheelite in the Mamupu deposit.

Application of EDTMPS as a novel calcite depressant in scheelite flotation

In this study, the innovative use of ethylenediamine tetramethylene phosphonic sodium(EDTMPS) as a calcite depressant in scheelite flotation was investigated by flotation experiments, and its selective depression mechanism was revealed by contact angle measurement, FTIR analysis, Zeta potential test and XPS analysis. The flotation experiment results showed that scheelite and calcite could be efficiently separated under the following conditions: pulp p H=9.5, Na OL concentration of 1.5×10^(-4)mol/L, EDTMPS concentration of 3.0×10^(-5)mol/L, a scheelite concentrate with WO3grade of 65.49%, recovery of 83.29%and separation efficiency of 65.29% could be obtained from the artificially mixed minerals. The analysis results of mineral surface properties demonstrated that EDTMPS was strongly adsorbed onto the calcite surface through the reaction between the phosphonate group and the calcium ions, which hindered Na OL adsorption and increased the hydrophilicity of calcite. However, EDTMPS had weak adsorption strength on the scheelite surface, which didn’t affect further adsorption of Na OL, hence, the scheelite remained hydrophobic. Consequently, the selective adsorption of EDTMPS on the two minerals’ surfaces increased a difference in wettability and thus enabling them to be separated by flotation. Finally, the mechanism model of this flotation separation process was established.

Flotation separation depressants for scheelite and calcium-bearing minerals: A review

Owing to the depletion of wolframite, the focus of tungsten extraction has gradually shifted to scheelite. However, separating the associated minerals(e.g., apatite, fluorite, and calcite) and scheelite is challenging because their surface physicochemical properties are similar to those of scheelite. Fortunately, researchers have made substantial progress in separating the minerals of scheelite by using depressants. This study reviews the application and inhibition mechanism of inorganic depressants in obtaining tungsten from its calcium-bearing minerals. The application of new organic depressants in obtaining tungsten from its calcium-bearing minerals and the associated mechanisms are also summarized. After an objective assessment of inorganic and organic depressants’ advantages and disadvantages, possible future research directions for inorganic and organic depressants are proposed. Herein, we provide a theoretical basis for developing scheelite flotation depressants.

Diffusion of Sm-Nd in Scheelite and its Significance to Isotopic Dating and Tracing

As the principal ore mineral in various tungsten(-gold)deposits,scheelite(CaWO_(4))plays an important role in directly dating the timing of ore formation,and in tracing associated material sources through the study of its Sm-Nd geochronology and Nd isotopic characteristics.Since the retention of Sm-Nd systematics within scheelite is presently unconstrained,equivocal interpretations for isotopic data resulting from this method have occurred quite often in previous studies that apply these isotopic data.In order to better elucidate the closure of Sm-Nd in scheelite,the kinetics of Sm and Nd within this mineral lattice were investigated through calculation of diffusion constants presented herein.The following Arrhenius relations were obtained:D_(Nd)=4.00exp(-438 kJ·mol^(–1)/RT)cm^(2)/s D_(Sm)=1.85exp(-427 kJ·mol^(–1)/RT)cm^(2)/s showing diffusion rate of Nd is near identical to Sm in scheelite when at the same temperature.However,compared to other rare earth elements(REEs),which have markedly different atomic radii to either Nd or Sm,these are shown to exhibit a great variation in diffusivities.The observed trends in our data are in excellent agreement with the diffusion characteristics of REEs in other tetragonal ABO4 minerals,indicating that ionic radius is a key constraint to the diffusivity of REEs in the various crystal lattices.With this in mind,the same substitution mechanism and a very slight discrepancy in radii will allow us to infer that significant Sm/Nd diffusional fractionation in scheelite is unlikely to occur during most geological processes.Based upon the diffusion data determined herein,Sm and Nd closure temperatures and retention times in scheelite are discussed in terms of diffusion dynamics.Those results suggest that closure temperatures for Sm-Nd within this mineral are relatively high in contrast to the temperature ranges of ore-formation responsible for scheelite-related deposits,and any later thermal environments.It is likely,therefore,that relevant isotopic information could be easily retained under most geological conditions,since initial crystallization of the scheelite.In addition,comparison of this mineral-element pair over a range of temperatures with some other common minerals used as geochronometers(e.g.,zircon and apatite)indicates that Sm-Nd system has a slower diffusive rate in scheelite than for Sr in apatite or Ar in quartz,and only a little faster than for Pb in zircon.It should be noted,within most hydrothermal deposits where zircon has crystallized,its size is typically no more than 100μm,whereas scheelite commonly occurs as macroscopic grains.For this reason,the larger dimensions of scheelite would provide a robust Sm-Nd system more able to resist perturbations,relating to any later thermal process.As such Sm-Nd investigations of scheelite are akin to U-Pb within zircon samples used in isotopic dating.These observations indicate that Sm-Nd age and isotopic information can provide reliable data in all but the most extreme case,especially when data are extracted from macroscopic grains of scheelite that are chosen to be“pristine”(i.e.,free of surface alteration and/or fractures).

Preparation of cinnamic hydroxamic acid collector and study on flotation characteristics and mechanism of scheelite

In this paper,using methyl cinnamate as raw material,the new cinnamic hydroxamic acid collector(CIHA)was synthesized by the hydroxylamine method.The collector performance of hydroxamic acid was investigated for scheelite and gangue calcite,and the flotation separation test of scheelite and calcite was carried out with CIHA as the collector.The interaction mechanism between hydroxamic acid and scheelite minerals has also been investigated through zeta potential,Fourier transform infrared spectroscopy(FTIR)experiments,X-ray photoelectron spectroscopy(XPS)experiments,and density functional theory(DFT)calculation.The single mineral flotation test and artificially mixed ore showed that CIHA had an excellent collection effect and selectivity.Zeta potential,FTIR,and XPS showed that CIHA was adsorbed on the scheelite surface by strong chemical adsorption.The active group of CIHA was analyzed through quantum chemical calculation.It was speculated that C=O and N-O bonds could synthesize a five-membered chelated hydroxamic acid group with Ca element chelate on scheelite surface,changing hydrophobicity and making it more likely to emerge from the pulp.

Surface energies and appearances of commonly exposed surfaces of scheelite crystal

Surface energies of five different surfaces of scheelite crystal were calculated using density functional theory （DFT）. Based on the calculation results, the predominantly exposed surfaces in the morphologies of scheelite crystals were predicted. {112} and {001} cleavage surfaces and {112} crystal surface are the commonly exposed surfaces, which are consistent with both previous literatures and the present experimental observations based on the XRD. Cleavage generates more easily along {112} surfaces than along {001} surfaces due to their different interlayer spacings. The surface roughness and appearance of different predominantly exposed surfaces were then investigated using AFM. The roughness of smooth {112} cleavage surface is the lowest among these three surfaces. On {001} cleavage surface, terraces are flat and separated by steps of about 10 nm in height. Subsequently, contact angle measurements were adopted to evaluate the wettability and surface energies of these surfaces. The surface energies evaluated directly correspond to the trend calculated with DFT.

Effects of particle size and particle interactions on scheelite flotation

Effects of size distribution (particle size and content of fine fraction (<10μm)) on scheelite flotation were studied using flotation tests and theoretical calculations. The results show that particle size influences the scheelite recovery and the performance of combined reagents. The scheelite recovery is lowered by adding fine particles (<10μm) into the pulp containing coarse particles. Extended DLVO (EDLVO) theory confirms that the fine fractions (<10μm) could interface with the coarse fractions. The interaction energy and fluid forces are relative to the particle size, which might explain why the fine fractions influence the scheelite flotation. The highest recovery of scheelite using combined reagents as collector and optimum ratio of combined reagents were determined by scheelite particle size and reagent performance. However, the optimum adding order was only determined by reagent performance, which has nothing to do with particle size.

A decomposing technique for scheelite concentrate and low-grade scheelite concentrate

The effect of different decomposition conditions on tungsten recovery forscheelite concentrate has been examined. The results show that tungsten recovery can be more than98% under decomposing conditions as follows: the amount of caustic soda is 2.2 and 3.2 times oftheoretical respectively, ratio of water and ore is 0.7-0.8, temperature is 160℃, and preservationtime is 2.0 h for scheelite concentrate (63.21 % WO_3) and low grade scheelite concentrate (55.17%WO_3).

Decomposing scheelite and scheelite-wolframite mixed concentrate by caustic soda digestion

Scheelite and scheelite-wolframite mixed concentrates with different grades were decomposed by caustic soda digestion, and the effects of caustic soda（NaOH） dosage, the ratio of water to ore and the stirring rate on tungsten recovery were studied. The results show that under the conditions that the ratio of water to ore is （0.8,） stirring rate is 500 r·min-1 and the heating time is 2.0 h at （160 ℃,） the recovery of tungsten reaches 98% for scheelite （w（WO3） is （65.04%）） and wolframite containing high proportion of calcium （w（WO3） is 65.58%, w（Ca） is （7.53%）,） when caustic soda dosage is 2.2 and 2.0 times of theoretical value, respectively; the recovery of tungsten can be more than 98%,98% and 96% respectively for low-grade scheelite-wolframite mixed concentrate with （55.78%,） 45.32% and 25.21% WO3, when caustic soda dosage is 2.6,3.2 and 5.5 times of theoretical value, respectively.

Froth flotation of scheelite – A review

Froth flotation of scheelite has regained new focus since the 2010s and research regarding floatability and reagents has made great progress over the years. The main objective was and remains the selective flotation of scheelite from other calcium-bearing minerals, in particular calcite, fluorite and apatite. Due to similar properties, most attempts have limited success or only specific application(linked to a type of ore or a location). This article aims at reviewing all general physical-chemical information on froth flotation of scheelite, including electrokinetic properties, influence of p H and already existing reagents as well as ones still under examination. It appears that chelating or mixed collectors and modified versions of sodium silicate and quebracho hold great promise for scheelite flotation, while the use of said depressants and/or promoters seems inevitable.

A novel green depressant for flotation separation of scheelite from calcite

Polyaspartic acid(PASP)was used as a novel environmental-friendly depressant,and its inhibition effect on flotation performance of scheelite and calcite using sodium oleate(NaOL)as a collector was investigated by ways of flotation experiments,zeta potential measurement,contact angle measurement and infrared spectroscopic analysis(IR).The results show that PASP exhibits stronger inhibition capability and selectivity than acidified water glass,and the flotation separation of scheelite from calcite can be realized in the presence of 6 mg/L PASP and 20 mg/L NaOL at pH>6.In the presence of PASP,the zeta potential of calcite surface almost keeps unchanged after adding NaOL,and the contact angle decreases sharply.Therefore,it is indicated that PASP significantly decreases the adsorption of NaOL on calcite surface.By contrast,it has no distinct effect on the adsorption of NaOL on the scheelite surface,which is further confirmed by IR results.

Review on development of low-grade scheelite recovery from molybdenum tailings in Luanchuan, China: A case study of Luoyang Yulu Mining Company

Luanchuan area is one of the regions with the largest scale of scheelite beneficiation and the largest output of scheelite concentrate in the world. After years of innovation and progress, the beneficiation technology of low-grade scheelite associated with molybdenum tailings in Luanchuan area is becoming more and more perfect. In this study, the development process of low-grade scheelite recycling technology in Luanchuan area was reviewed, including raw ore properties, beneficiation process, flotation equipment and flotation reagents. Meanwhile, taking Luoyang Yulu Mining Co., Ltd. as an example, the effects of various technical transformations such as the optimization of the beneficiation process, the column-machine combined process, and the high-efficiency flotation reagents were elucidated in detail. However, the recycling technology of low-grade scheelite of Luanchuan area is still possible to be improved. As a result, coupled with the latest research progress, the development direction of low-grade scheelite beneficiation in Luanchuan area was also prospected. It is of great significance to further improve the recovery efficiency of low-grade scheelite resources in Luanchuan area and this can provide technical reference for other scheelite plants.

Comparative kinetic analysis of conventional and ultrasound-assisted leaching of scheelite by sodium carbonate

For further comprehending the mechanism of the intensification of ultrasound for extraction,the difference of leaching kinetics between the ultrasound-assisted and conventional sodium carbonate leaching of scheelite was studied,and the corresponding kinetic equations were established.The results indicate that the obtained apparent activation energy with or without ultrasound is same 72 kJ/mol,and both reactions are controlled by surface chemical reaction.By comparing the leaching kinetics of scheelite by Na2CO3,NaOH and Na3PO4 reactants with or without ultrasound,a general conclusion for scheelite hydrometallurgy is obtained.For the process with the formation of compact product layer,the intensification of the tungsten extraction with ultrasound mainly reflects in the stripping and elimination of product layer,corresponding to the transformation of kinetic controlling step from diffusion controlling step and reduction of apparent activation energy.For the one without compact product layer or with a loose and porous product layer,the intensification mainly embodies in the increase of frequency factor,and the controlling step and apparent activation energy of the reaction always remain constant.

Leaching kinetics of scheelite concentrate with sodium hydroxide in the presence of phosphate

The reaction kinetics for the leaching of low-grade scheelite concentrate was investigated in an autoclave with sodium hydroxide in the presence of phosphate. The effects of stirring speed (300-600 r/min), reaction temperature (353-383 K), sodium hydroxide concentration (1.69-6.76 mol/L) and phosphate concentration (0.68-1.69 mol/L) on the WO3 dissolution ratio were studied. The results showed that the WO3 dissolution ratio was practically independent of stirring speed, while it increased with increasing the reaction temperature, and the concentrations of sodium hydroxide and phosphate. The experimental data were consistent with the shrinking core model, with a surface chemical reaction as the leaching rate-determining step. The apparent activation energy was calculated as 49.56 kJ/mol, and the reaction orders with respect to the concentrations of sodium hydroxide and phosphate were determined as 0.27 and 0.67, respectively. The kinetics equation of the leaching process was established.

Collecting performance of vegetable oils in scheelite flotation and differential analysis

The composition of a collector directly affects its collecting performance in mineral flotation.In this study,three vegetable oils were used as the collectors,the flotation performance of scheelite and the differential analysis were studied through flotation experiments,zeta potential,contact angle measurement and Fourier transform infrared spectrum(FTIR)analysis.Flotation results show that the recovery of scheelite increases in the order of oleic acid<rapeseed oil<rice bran oil<soybean oil,especially in the pH range of 5-8.The distinction in the scheelite recovery is due to the different compositions of these collectors.The addition of LA,LNA and PA(<5%)can increase the recovery of scheelite with OA,but the addition of SA deteriorates the scheelite flotation.Results of zeta potential,contact angle measurement and FTIR analysis indicate that the collector adsorption on scheelite surface is enhanced when using the three vegetable oils.For the raw ore with 0.086%WO3,a rough concentrate containing 1.423%WO3 with the recovery of 84.22%is obtained using soybean oil as the collector.

Selective depression behavior of guar gum on talc-type scheelite flotation

The depression behavior and mechanism of guar gum on talc-type scheelite flotation were systematically investigated by flotation experiments, adsorption tests, zeta-potential measurements, and infrared spectroscopic analyses. The flotation results for monominerals, mixed minerals, and actual mineral samples indicated that guar gum exhibited much higher selective depression for talc than for scheelite. Bench-scale closed-circuit tests showed that a tungsten concentrate with a WO_3 grade of 51.43% and a WO_3 recovery of 76.18% was obtained. Adsorption tests, zeta-potential measurements, and infrared spectral analyses confirmed that guar gum absorbed more strongly onto the talc surface than onto the scheelite surface because of chemisorption between guar gum and talc. This chemisorption is responsible for the guar gum's highly selective depression for talc and small depression for scheelite. The flotation results provide technical support for talc-type scheelite flotation.

CAUSTIC DECOMPOSITION OF SCHEELITE AND SCHEELITE－WOLFRAMITE CONCENTRATES THROUGH MECHANICAL ACTIVATION

Based on physicochemical study of the reaction between scheelite and NaOH, a new decomposition process for scheelite and scheelitewolframite concentrate, i. e., mechenically activating caustic decomposition has been developed, and it has been successfu