Selective flotation of scheelite from calcium minerals with sodium oleate as a collector and phosphates as modifiers. I. Selective flotation of scheelite

The effects of Na₂SiO₃, Na₃PO₄, Na₄P₂O₇, (NaPO₃)₆, quebracho, tannic acid and S 808 (sulphonated product of rough phenantrene) on the floatability of the following five pure minerals: scheelite, calcite, fluorite, garnet and quartz, with sodium oleate as collector were investigated in detail as well as the role of pH on these effects. The results obtained indicate that Na₄P₂O₇ and (NaPO₃)₆ were effective modifiers for the selective flotation of scheelite. The results of the batch flotation tests on mixtures of these minerals showed that the recovery of scheelite from scheelite-silicate mixtures (31% WO₃) with (NaPO₃)₆ or Na₄P₂O₇ increased by 20% as compared with sodium silicate and the WO₃ grade of the concentrate by 5%. At room temperature, the scheelite-calcium mineral mixtures could not be separated with sodium silicate. In the separation of these mixtures with the phosphate modifiers, a concentrate grade of 47–60% WO₃ was obtained at 70–90% recovery. This showed that the flowsheet of the selective flotation of scheelite with phosphate modifiers may replace the conventional Petrov's process.     

Efficient flotation recovery of lead and zinc from refractory lead-zinc ores under low alkaline conditions

In this study, a new flotation approach, a low-alkaline and non-desliming process, was introduced for improving lead and zinc recoveries, lowering production cost and reducing environmental pollution. Lab-scale experiments results show that the new process contributed to the flotation of the complex mixed sulfide-oxide lead and zinc ore regarding two aspects: (1) High alkaline process (pH = 12±) was replaced by low alkaline process (pH = 9±) by using collector WS (a mixture of ethyl thiocarbamate, ammonium dibutyldithiophosphate and dithiophosphate-25) and combined depressant Na₂S/ZnSO₄/Na₂SO₃ for lead sulfide flotation; (2) Non-desliming process was successfully achieved by using collector MA (a mixture of ether amine, hydroxyethyl cellulose and polyacrylic acid) and combined depressant SHP/SS (sodium hexametaphosphate/sodium silicate) for zinc oxide flotation. And 43.37% Pb in the Pb concentrate was recovered, the corresponding Pb grade was 52.73%, total 84.42% Zn was recovered by the flotation of zinc sulfide minerals and zinc oxide minerals. Moreover, the two aspects of the new approach were systematically verified from lab-scale to industrial-scale application. The industrial-scale flotation tests show that Pb recovery in Pb concentrate increased by 1.86% compared with that of original system during industrial-scale tests period, and the Pb recovery increased by 4.09% compared with that of original system before industrial-scale tests period, while the Zn operating recovery in zinc oxide concentrate improved by 19.52%. Moreover, the total reagent cost of the whole new process significantly declined by 3.93 yuan per ton of ore.     

Flotation of calcareous Mussorie phosphate ore

Separation of Mussorie rock phosphate (P₂O₅ = 20%) from Uttar Pradesh, India, containing pyrite, calcite and other carbonaceous impurities by flotation has been successfully attempted to upgrade the phosphate values. Based on Hallimond cell flotation results of single and synthetic mineral mixtures of calcite and apatite using oleic acid and potassium phosphate, conditions were obtained for the separation of calcite from apatite which is considered to be the most difficult step in the beneficiation of calcareous phosphates. Further studies using 250 g of the mineral (?60 +150 and ?150 mesh fractions, deslimed) in laboratory size Fagergren subaeration machine employed a stagewise flotation viz. carbonaceous materials using terpineol, pyrite using potassium-ethyl xanthate and calcite using oleic acid respectively. Separation was, however, found to be unsatisfactory in the absence of a depressant.Among starch, hydrofluosilicic acid and dipotassium hydrogen phosphate, which were tried as depressants for apatite in the final flotation stage, dipotassium hydrogen phosphate proved to be superior to others. However, the tests with the above fractions did not yield the required grade. This was possibly due to insufficient liberation of the phosphate mineral from the ore body and different experimental conditions due to scale up operations. Experiments conducted using ?200 mesh deslimed fractions has yielded an acceptable grade of 27.6% P₂O₅ with a recovery of about 60%. The results have been explained in terms of the specific adsorption characteristics of phosphate ions on apatite and the liberation size of the mineral.     

Selective flotation of scheelite from calcium minerals with sodium oleate as a collector and phosphates as modifiers. II. The mechanism of the interaction between phosphate modifiers and minerals

The respective effects of phosphate modifiers on the solubility of calcium minerals in water, on the surface charge of the minerals and on the adsorption of the phosphates and of sodium oleate on the mineral surface were examined. The Auger spectra and the infrared spectra of the minerals treated with these reagents were also investigated. The ability of the phosphates to complex metal ions was determined by nephelometric titration. The structures of the minerals and their effects on their floatability, as well as structures of the phosphates and their effects on the complexation power were discussed. A mechanism of depression of the calcium minerals through the selective complexing dissolution of calcium ions from the mineral surface was derived and explains the higher selectivity obtained in scheelite flotation when (NaPO₃)₆ or Na₄P₂O₇ are used as modifiers.     

Interactive effects of the type of milling media and CuSO4 addition on the flotation performance of sulphide minerals from Merensky ore Part II: Froth stability

The limitations of pulp chemistry measurements in the flotation of a platinum group mineral (PGM) bearing Merensky ore were demonstrated in Part 1 of this article. In this paper the importance of the contribution of the froth structure due to changing froth stability is analysed using the batch flotation data. The effects of mild steel (MS) and stainless steel (SS) milling media and the addition of copper sulphate on the flotation performance of the sulphide minerals in Merensky ore have been evaluated in relation to the changes in stability of the froth phase. The effects of pulp chemistry and froth stability on the flotation of sulphide minerals were distinguished by using two different rate constants (k_t and k_w). The rate constant (k_w) calculated as a function of cumulative water recovery was used to describe characteristics of froth phase and k_t was calculated as a function of flotation time. The results revealed that the type of grinding media and copper sulphate addition had an interactive effect on the froth stability. While mild steel (MS) milling increased the froth stability due to the presence of hydrophilic iron hydroxides and colloidal metallic iron, the addition of copper sulphate reduced the stability, especially with stainless steel (SS) milling. Copper sulphate addition had a dual role in the flotation of Merensky ore in that it caused destabilisation of the froth zone as well as activation of selected sulphide minerals. The dominant effect was found to depend on the type of milling media and floatability of the mineral in question and this work has demonstrated the importance of using a combination of measurements to evaluate flotation performance holistically.     

Physical and thermal treatment of phosphate ores — An overview

The annual consumption of phosphate rock approached 150 million tons. The marketable phosphate is usually 30% P₂O₅ or higher. The run-of-mine material is mostly of lower grade which needs processing or upgrading. The processing techniques of phosphate ores depend mostly on the type of associated gangue minerals present in the mined rock. In some cases, simple, inexpensive techniques are enough to produce the required grade. For example, crushing and screening is used to get rid of the coarse hard siliceous material, and attrition scrubbing and desliming is used to remove the clayey fine fraction. If silica is the main gangue material, single-stage or double-stage flotation is the conventional mineral processing technique used in this case. If the ore is igneous carbonatitic alkaline or ultra basic phosphate deposit, crushing, grinding, scrubbing, and flotation associated with other steps such as magnetic and/or gravity separation is proved to be successful in upgrading this type of ore. The sedimentary phosphate ores having carbonate-apatite as the main phosphate minerals and containing carbonates (calcite and/or dolomite) represent a challenge in the field of phosphate concentration due to similarity in the physico-chemical properties of surfaces of the ore constituents. Also, if considerable amount of organic matter constitutes the main gangue material, upgrading of the ore becomes difficult. New flotation systems (techniques and reagents) are being developed to treat these challenging phosphate ores. Furthermore, calcination is another solution for upgrading these difficult-to-treat types of ores. However, calcination is indicted with some controversial drawbacks. This overview discusses and summarizes the State-of-the-Art and the existing efforts to overcome these problems and to produce a high-grade phosphate product suitable for fertilizers and other phosphate compounds.     

Pre-concentration and residual bitumen removal from Athabasca oilsands froth treatment tailings by a Falcon centrifugal concentrator

Both froth flotation and centrifugal concentration were used to pre-concentrate the oil sands froth treatment tailings prior to the recovery of heavy minerals (titanium and zirconium minerals). Over 90% of the heavy minerals were recovered into a bulk flotation concentrate that was about 50% of the feed mass at 85 °C without any reagents. The same recoveries were obtained at 50 °C with the addition of NaOH and/or sodium oleate. However, the flotation concentrate also recovered over 90% of the residual bitumen and much of the clays/slimes. Subsequent treatment of the flotation concentrate such as dewatering and bitumen removal would be difficult due to these residual bitumen and clays. On the other hand, a SB40 centrifugal concentrator recovered over 85% of the heavy minerals but less than 30% of the residual bitumen. With improved liberation the recovery of the residual bitumen into the concentrate could be further reduced. The particle sizes of the SB40 concentrates were also larger than the flotation concentrates, making subsequent processing much easier.     

Proposed upgrading techniques for East Sibaiya phosphorites,Aswan area,southern Egypt

The Late Cretaceous (Campanian-Maastrichian), low-grade phosphorite sequence of East Sibaiya, Aswan area, which is known as the Duwi (phosphate) or Sibaiya Formation, is usually intercalated with marl, oyster limestone, and chert beds. These strata, which crop out in a generally east–west trending belt spanning the middle latitudes of Egypt, are phosphorite-rich sediments and of great economic importance. Representative samples were collected from the investigated area at several localities (e.g., Umm Tundubah-2 and Wadi El-Batur) and 200 kg of phosphate rocks was used for upgrading processes of low-grade phosphorites of the East Sibaiya area. The upgrading processes included two techniques: the first technique (gravity separation) comprises crushing, sieving, gravity separation by a shaking table, and magnetic separation. This technique raised the P₂O₅ in the head sample from 24.73 to 31.91% as a phosphate concentrate. The second technique (flotation technique) depends on certain flotation parameters such as pH, grain size, and phosphate collector dose (i.e., oleic acid). The flotation technique increased the P₂O₅% from 24.73 to 31.16% as a final product of the phosphate concentrate. These data were confirmed by X-ray fluorescence analyses of major elements.     

粉石英与红柱石的浮选分离机理研究

本文以油酸钠作为捕收剂,研究了磷酸氢二钠、柠檬酸和硅酸钠等抑制剂对粉石英与红柱石浮选分离效果的影响.结果表明,磷酸氢二钠是红柱石与粉石英浮选分离的一种优良的抑制剂;在其最佳浓度0.47×10-2 mol /L,浮选液pH值为8.5时,粉石英与红柱石浮选回收率差高达47.86％.红外光谱及Zeta电位分析结果表明,油酸钠对红柱石兼有物理和化学吸附作用,对粉石英仅有物理吸附作用,因而对红柱石有更强的捕收能力;磷酸氢二钠对粉石英表面起解吸作用,能有效抑制粉石英起浮,从而实现粉石英与红柱石的分离.     

Effects of an ultrasonic field on the flotation selectivity of barite from a barite-fluorite-quartz ore

The influence of an ultrasonic field frequency of 22 kHz and intensity of 0.5 W/cm² has been examined on the flotation of barite, fluorite and quartz as well as on their ability to adsorb dodecyl- and cetylsulphates. The tests affected the flotation of pure minerals in a Hallimond tube as well as the flotation of a natural barite-fluorite ore. It has been found that ultrasonic pretreatment of minerals causes an increase in the flotation rate of barite and a decrease in the flotation rate of fluorite. Ultrasonic pretreatment of the natural barite-fluorite ore before its flotation is the most advantageous. In this case it is possible to obtain concentrates of barite composed of a low amount of CaF₂. This may be explained by the different effects of ultrasonic vibrations on barite and fluorite which cause some improvement of the selectivity of their flotation separation.For a full explanation of these results the effects of ultrasonic pretreatment of the minerals on their adsorption properties and surface topography have been investigated, as well as the direct influence of ultrasound on the adsorption process.     

Optimisation of operating variables of fine coal flotation using a combination of modified flotation parameters and statistical techniques

Optimisation of flotation parameters using rate models is not a new concept. The kinetic model based on time recovery data, which uses the extra dimension of rate, has been in vogue since time immemorial for scaling up of lab data. Often, interpretation on the performance of a flotation circuit, based only on R_∞ (the ultimate recovery) and k_s (the first-order rate constant of the component) may lead to wrong conclusions. In such cases, a modified flotation rate constant k_mod defined as the product of R_∞ and k_s, i.e., k_mod=R_∞k_s and selectivity index (SI), defined as the ratio of the modified rate constant of valuables to the modified rate constant of gangue, can be used. An attempt has been made in this paper to optimize the batch laboratory froth flotation parameters of fine coal using the above two concepts, i.e., k_mod and SI and statistical techniques.A flotation bank containing four Outukumpu cells was optimized using the results obtained from the lab study. The airflow number and the froth number were used as a basis for scale up. To gauge the performance of the froth flotation circuit, an efficiency parameter called the coefficient of separation or the CS was used. The yield from the flotation circuit improved, the froth ash reduced and the rejects ash went up.     

Removal of lead minerals from copper industrial flotation concentrates by xanthate flotation in the presence of dextrin

Potato starch and dextrins resulting from thermolysis of potato starch in the absence of reagents and presence of -amino acids are promising depressants for separation of lead and copper minerals present in the Polish industrial copper concentrates. The polysaccharides were used for differential xanthate flotation of the final industrial concentrates produced by flotation with sulfhydryl collectors in the absence of depressants. The polysaccharides depressed galena and provided froth concentrate rich in chalcocite and other copper minerals as well as cell product containing lead minerals. The best results of separation were obtained in the presence of plain dextrin prepared by a thermal degradation of potato starch. The industrial concentrate containing 18.5% Cu and 5.5% Pb was divided into a froth product containing 38.1% Cu with 77% recovery of copper and a cell product assaying 7.3% Pb with 83% recovery of lead. It was accomplished using 2500 g/t of dextrin, 50g/t of potassium ethyl xanthate, and 50 g/t of frother (α-terpineol). The pH of flotation was 8.0–8.2.     

The selective flotation of enargite from other copper minerals — a single mineral study in relation to beneficiation of the Tampakan deposit in the Philippines

The floatability of enargite (3Cu₂S.As₂S₅) has been determined as a function of pulp potential to establish whether the flotation behaviour of the mineral differs sufficiently from that of other copper minerals thus offering the prospect of rejecting arsenic from the Tampakan ore by potential control during flotation.     

Upgrading of calcareous phosphate ores by flotation: Effect of ore characteristics

Sedimentary phosphates contain-besides the phosphate minerals-, various associated gangue minerals such as: clays, silica, calcareous minerals (mainly calcite and dolomite), carbonaceous matter, iron oxides and/or pyrite. The common practiced flow-sheets for concentrating these types of phosphate ores consist of a combination of various mineral processing units such as: crushing and screening, attrition, washing, magnetic separation, and/or flotation. However, none of these combinations was successfully efficient to upgrade the calcareous ores because of the close similarity of the physical properties (density, particle size, particle shape, etc.) as well as the surface physico-chemical properties of the carbonate and phosphate minerals. For the last five decades extensive efforts have been spent to adopt flotation for separating carbonates from phosphate ores. These efforts include thermodynamic analysis, modification of the technique, controlling the pulp environment, and finding new reagents that can specifically differentiate between carbonates and phosphates.This paper reviews some of the published work on the separation of carbonates from phosphate ores by flotation and presents the flotation results of phosphate ore samples different in their physical properties and mineralogical composition. The results obtained reflect the effect of ore nature on the flotation performance and the reagents consumption.     

Interactive effects of the type of milling media and copper sulphate addition on the flotation performance of sulphide minerals from Merensky ore Part I: Pulp chemistry

It is well known that the chemical environment determines the success of the flotation process, however its characterisation and control is difficult to achieve. This paper, as two parts, Part I and Part II, evaluates the use of various measurements and their interpretation to gain an understanding of the influence of varying parameters such as the type of milling media and copper sulphate addition on the flotation performance of sulphide minerals from a platinum group mineral (PGM) bearing Merensky ore. It shows the complexity of interpretation and the importance of analysing flotation performance holistically. Part I focuses on the pulp chemistry and mineral potential measurements have been used to show the differences in the response of the various mineral electrodes to different conditions. The final flotation recoveries of the sulphide minerals in the ore followed the same trend as the decrease in mineral potential due to collector addition viz. chalcopyrite > pentlandite > pyrrhotite. Type of milling media and copper sulphate addition slightly affected the mineral electrode potential and flotation recovery of chalcopyrite. Addition of copper sulphate increased the recovery of pentlandite and particularly pyrrhotite due to activation by copper (II) ions. The copper activation mechanism was likely to be in the form of initial adsorption of copper hydroxide followed by reduction to Cu⁺ at the surface. However, the changes in flotation performance of the different minerals in the ore could not be completely described by the electrochemical changes, demonstrating the limitations of these measurements. Part II addresses the effect of froth stability as demonstrated by the variations in the mass and water recovery data resulting from the different milling conditions and addition of copper sulphate which emphasised the importance of considering the froth phase in the evaluation of flotation data.     

Rejection of arsenic minerals in sulfide flotation — A literature review

Arsenic is one of the most dangerous inorganic pollutants and thus a penalty element in many base metal concentrates. Arsenic removal in sulphide flotation has been studied extensively with various approaches, including pre-oxidation of flotation pulp, E_h control during flotation and the use of selective depressants/collectors. Pre-oxidation of flotation pulp using oxidizing agents or aeration conditioning represents a simple approach in arsenic removal and was found effective in many cases. Selective flotation of arsenic minerals through E_h control has made significant advances in recent years with promising results achieved. In addition, various depressants and collectors have also been studied in arsenic removal. In this communication, the various approaches used in selective flotation of arsenic minerals are reviewed with emphasis on the development in recent years.     

Microlaboratory study on magnetic,gravity and high-tension separation of hercynite and pleonaste from low-grade ilmenite concentrates

Some ilmenite concentrates obtained from oleate flotation of ilmenite ores from NE Poland contain less than the required 45% TiO₂ due to the presence of green spinels (hercynite and pleonaste). Such concentrates were further upgraded by different separation techniques. It was established at microlaboratory scale that magnetic, gravity and high-tension separations can provide qualified ilmenite concentrates with TiO₂ recovery in the order of 50 to 80%.     

Concentration of K-feldspar from a pegmatitic feldspar ore by flotation

Abundant reserves of Na-feldspar (albite) and K-feldspar (orthoclase or microcline) are found in granites, syenite, tracite and pegmatites. As both feldspar minerals have similar chemical structure and physicochemical properties, their separation is challenging. Flotation is known to be the only technique to enable their separation. The fundamentals on the separation of these minerals were well documented in our earlier studies. In this study, a pegmatite ore with a K₂O/Na₂O (3.78:3.37) ratio of 1.12 was studied in a Denver flotation cell both at natural and acidic pH using HF and H₂SO₄. Because of the perthitic structure of the ore no significant separation is observed at natural pH. Interestingly, a selective separation was achieved at low pH using HF and H₂SO₄ (pH 2.5–2.8). The selectivity is induced by the addition of Na⁺ ions through depression of albite. Selective separation has been carried out by stagewise flotation using the tree technique. Accordingly, a pegmatite ore composed of 3.37% Na₂O and 3.78% K₂O is upgraded to 10.51% K₂O and 3.02% Na₂O with a K₂O/Na₂O = 3.48 in HF medium and to 2.55 in H₂SO₄ medium. It is shown that products recovered in other stages are also considered as commercially significant. Especially, quartz, which is recovered in the tailings in HF medium, is suitable for glass industry. The overall results show that commercial utilization of these results is possible.     

Electrokinetic properties and flotation behaviour of apatite and calcite in the presence of sodium oleate and sodium metasilicate

Calcite is generally associated with apatite minerals in phosphate deposits. To explore the possibility of separating these minerals by a soap flotation technique, their electrokinetic properties and flotation behaviour were studied in the presence of sodium oleate.Microelectrophoresis data indicate oleate adsorption on these minerals, and from Hallimond-tube flotation tests it has been noted that in a controlled pH environment and for a certain sodium oleate concentration range, separation of these minerals is possible.The study of apatite/calcite-sodium metasilicate-sodium oleate systems indicates the preferential adsorption of silicate at the calcite surface. This suggests the potential use of sodium metasilicate as the modifying agent for the separation of apatite from calcite by depressing calcite when using sodium oleate as collector.