Flotation Of Dolomite Research Articles

A selective flotation of fluorite from dolomite using caustic cassava starch and its adsorption mechanism: An experimental and DFT Study

Due to the small difference in floatability between dolomite and fluorite, the problems of low grade of fluorite concentrate occur. It is very important to find a depressant that can selectively inhibit the floating of dolomite. As a natural polymer, starch is often used as a gangue depressant because of its low price and easy availability. In this paper, the effects of caustic cassava starch (CS) on the single mineral flotation performance of fluorite and dolomite and the flotation separation of mixed ore were studied. Its selective inhibition mechanism was investigated. The results of flotation tests with single minerals stated that the flotation of dolomite was vastly inhibited, while the fluorite was hardly affected when CS was added in flotation using sodium oleate as the collector. The concentrate grade of artificially mixed ore flotation fluorite reached 90.15%, and the recovery rate was 89.54%. The physical adsorption of CS on the surface of dolomite blocked the adsorption of hydrophobic sodium oleate on the surface of dolomite, thus depressing dolomite. The adsorption energy of dolomite and CS was much larger than that of fluorite and CS. This greatly deteriorated the flotation of dolomite and achieved flotation separation between fluorite and dolomite. The results demonstrate that CS is a promising depressant for dolomite in fluorite flotation.

Effects of common ions on the flotation of fluorapatite and dolomite with oleate collector

In this study, the effects of common ions, especially Ca2+, on the reverse flotation of fluorapatite and dolomite in acidic conditions with NaOL collector were investigated using micro-flotation, zeta potential, contact angle, adsorption analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and density functional theory-based first principal calculations. It is found that the dolomite flotation recovery was enhanced and the fluorapatite flotation was depressed by the addition of CaCl2 at pH 5. For dolomite, in the presence of CaCl2, the solubility of metal ions was increased, especially for Ca2+. The Ca and Mg sites exposed on the dolomite surface, increased the NaOL adsorption, thus, enhancing the dolomite flotation. However, the formation of Ca(H2PO4)2 species on fluorapatite surface inhibit its flotation.

Double roles of sodium hexametaphosphate in the flotation of dolomite from apatite

Sodium hexametaphosphate (SHMP), as a common flotation agent, is widely used in various mineral processing. In this study, effects of SHMP on the flotation of fine apatite and dolomite were investigated. It was proved to play a role as depressant for both of the minerals by single and artificially mixed minerals flotation, while the effective improvement of apatite concentrates under low amount SHMP addition demonstrated that it worked as another unknown role. Solution chemistry analyses, zeta potential measurements, X-ray photoelectron spectroscopy (XPS) and DLVO calculation were carried out to systematically investigate the corresponding mechanism of SHMP effect in the flotation process. DLVO theory calculation verified the dispersion function of SHMP for mineral particles. Hence, SHMP played double roles in the flotation process. On the one hand, it worked as a depressant by increasing the hydrophilicity of apatite, through promoting the formation of CaHPO4 and Ca(H2PO4)2 on the apatite surface. On the other hand, it acted as a dispersant by increasing the total interaction energy between apatite and dolomite mineral particles, enhancing the dispersion of dolomite and adhesion of agents and bubbles to the minerals. Both roles were favorable for the separation of mixed minerals in flotation.

Simultaneous separation of quartz and dolomite from magnesite using monosodium phosphate as a regulator via reverse flotation

In this study, monosodium phosphate (MSP) was used as a regulator for simultaneous separation of quartz and dolomite from magnesite with dodecylamine (DDA) as a collector via reverse flotation. The results of micro-flotation tests indicated that MSP had a selective activation effect on the dolomite flotation, which made the flotation behavior of dolomite similar to that of quartz under DDA as a collector. Further, batch flotation results showed that MSP could effectively simultaneous removal of quartz and dolomite from magnesium-bearing carbonate ores. Contact-angle tests revealed that MSP could selectively increase the contact angle of dolomite, resulting in the high hydrophobicity of dolomite in the presence of DDA, but it has no such effect on magnesite and quartz surface. Field emission scanning electron microcopy (FESEM) with an energy dispersive X-ray spectrometer (EDS) detection suggested that MSP was mainly adsorbed on dolomite and changed its surface characteristics rather than quartz and magnesite. Based on the Fourier transform infrared (FTIR) analysis, MSP could selectively improve the adsorption of DDA onto the dolomite surface.

Analysis of selective modification of sodium dihydrogen phosphate on surfaces of magnesite and dolomite: Reverse flotation separation, adsorption mechanism, and density functional theory calculations

In the present work, the flotation separation of magnesite from dolomite was enhanced using sodium dihydrogen phosphate (SDP) as an activator for dolomite and dodecylamine (DDA) as a collector. Based on the findings of micro-flotation examinations, SDP possessed selective-activation effects on the dolomite flotation; however, it had no such effect on the magnesite flotation. Zeta potential measurements revealed that SDP, with its negatively charged functional group, could selectively reduce the dolomite surface potential, which promoted the adsorption of DDA with cationic functional groups on the dolomite surface, while it only included a slight impact on the magnesite. Fourier transform infrared (FTIR) analysis revealed that SDP could be adsorbed selectively on the dolomite surface. Based on the X-ray photoelectron spectroscopy (XPS) analysis, SDP could selectively improve the adsorption of DDA onto the dolomite surface, and also proved that the SDP adsorption selectively onto dolomite could be related to the selective reaction with Ca. Density functional theory (DFT) calculations indicated that the spontaneous adsorption interaction intensity between magnesite and SDP was considerably weaker than that between SDP and dolomite.

Sodium tripolyphosphate as a selective depressant for separating magnesite from dolomite and its depression mechanism

Efficient separation of magnesite from dolomite remains challenging owing to the similar floatability of the two minerals. Therefore, understanding the adsorption behaviors of surfactants (depressants and collectors) on their surfaces is essential for improving separation efficiency. In this study, the ability of sodium tripolyphosphate (STPP) to separate magnesite from dolomite was evaluated in sodium oleate (NaOl) systems, with an emphasis on its effect on the depression of dolomite. The mechanisms underlying the differential adsorption and depression of STPP were investigated through surface analyses, namely Fourier transform infrared spectroscopy, zeta-potential analysis, adsorption-quantity analysis, and X-ray photoelectron spectroscopy. The flotation results indicated that STPP facilitated the removal of dolomite from magnesite in the NaOl system because it significantly depressed dolomite, whereas its effect on magnesite was negligible. Surface analyses revealed that the preferential adsorption of STPP on dolomite was due to the interaction between the –PO4 tetrahedra of STPP and Ca sites. Furthermore, in the presence of STPP, small amounts of NaOl were adsorbed onto dolomite, inhibiting the flotation of dolomite. However, substantial amounts of NaOl were adsorbed onto magnesite, maintaining the good floatability of magnesite. Therefore, STPP can be considered as a promising depressant for separating magnesite from dolomite via direct flotation.

Selective flotation separation of apatite from dolomite utilizing a novel eco-friendly and efficient depressant for sustainable manufacturing of phosphate fertilizer

Phosphate ores upgraded by froth flotation are widely used as vital raw materials for the sustainable production of phosphate fertilizer to maintain the food supply. In the flotation process, the efficient recovery of apatite from dolomite-bearing phosphate ore for phosphate fertilizer production depends significantly on the use of high-selectivity depressants. At present, traditional depressants used for phosphate ore flotation (e.g., sulfuric acid, phosphoric acid, cellulase enzyme, and β-naphthyl sulfonate formaldehyde condensate) have several disadvantages in practice, such as large dosages, poor selectivity, and high toxicity, resulting in high costs, low efficiency, and potential environmental damage in practice. Therefore, this study proposed a novel eco-friendly depressant, namely, acrylic acid-2-acrylamido-2-methylpropanesulfonic acid copolymer (P (AA-AMPS)), for the effective recovery of apatite from dolomite-bearing phosphate ore using a collector, sodium oleate (NaOl). The separation performance and adsorption mechanisms of P (AA-AMPS) onto apatite and dolomite were systematically explored via flotation experiments, infrared spectral (IR) detection, surface electrical characterization, X-ray photoelectron spectroscopy (XPS), and adsorption capacity studies. Micro-flotation results indicated that the addition of P (AA-AMPS) could achieve the efficient separation of apatite from dolomite at pH 8.5 by selectively depressing the dolomite flotation, in which more than 87.4% of apatite was recovered whereas the dolomite recovery was less than 14.7%. Surface analyses demonstrated that much greater amounts of P (AA-AMPS) were adsorbed onto dolomite than apatite, which might be attributed to the intense interaction of P (AA-AMPS) with magnesium sites of dolomite. Furthermore, the pre-adsorption of P (AA-AMPS) substantially prevented NaOl from being adsorbed onto dolomite, thereby strongly depressing its flotation. However, the significant adsorption of NaOl onto apatite contributed to its excellent floatabilty even in the presence of P (AA-AMPS). As a result, P (AA-AMPS) could accomplish the effective removal of dolomite from phosphate ore, as demonstrated by the high-quality apatite concentrate that was produced, which had a P2O5 grade of 38.53% and a MgO grade of 0.85%. Thus, P (AA-AMPS) can be considered as an eco-friendly and efficient depressant in the effective removal of dolomite to obtain clean apatite from phosphate ore via direct flotation for the sustainable manufacturing of phosphate fertilizer.

Differential adsorption of hydrolytic polymaleic anhydride as an eco-friendly depressant for the selective flotation of apatite from dolomite

Differential adsorption of surfactants (e.g., collectors and depressants) on the minerals plays a key role in mineral flotation through selectively altering the surface wettability of minerals. In this study, to improve the removal efficiency of dolomite from apatite by direct flotation, hydrolytic polymaleic anhydride (HPMA) was introduced as an eco-friendly depressant for dolomite. The depressing performance and adsorption mechanism of HPMA on the dolomite and apatite surfaces were studied through flotation tests and surface analyses. Flotation results demonstrated that HPMA displayed an intense depressing impact on the dolomite flotation while affected slightly the apatite flotation. Surface wettability analysis indicated that the selective adsorption of HPMA at the dolomite/water interface declined significantly the dolomite hydrophobicity even in the case of sodium oleate (NaOl). Surface adsorption detection and zeta-potential results demonstrated that HPMA had a much stronger interaction with dolomite than apatite, resulting in the intense adsorption of HPMA onto dolomite. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) further evidenced that compared with apatite, the strong interaction between HPMA and magnesium sites of dolomite enhanced the chemisorption of HPMA onto dolomite surface, which prevented strongly NaOl adsorption onto dolomite. As a result, dolomite was strongly depressed by HPMA to achieve the effective recovery of apatite. Based on these findings, HPMA can be potentially utilized as an eco-friendly and high-selectivity depressant for removing dolomite from apatite.

Influence of the pH regulator on the dolomite hydrophobization process

Abstract A study was carried out to investigate the combined effect of released ions in the pulp by pH regulator and mineral surface on dolomite flotation. The tests were carried out using a dolomite sample in a bench flotation cell with automatic froth remover. Zeta potential measurements, solution conductivity and FTIR analysis were done to support the interpretation of the results. The main reagents used for pH adjustment in the alkaline range (calcium hydroxide, sodium hydroxide, and sodium carbonate) were compared using amine or sodium oleate as collector. Dolomite is a sparingly soluble-type calcium mineral (as calcite, apatite, fluorite and scheelite), releasing differ ent amounts of calcium and magnesium ions in the pulp. Amine adsorbs mainly by a chemical complexation mechanism between the molecular specie RNH2 with calcium and magnesium ions present on the dolomite surface. In this system calcium hydroxide must be used because in addition to adjusting the pH it is a calcium ion supplier, thus increasing the collector adsorption. In turn, in the dolomite flotation with oleate, the pH must be regulated with soda ash that precipitates Ca2+ and Mg2+ as carbonate al lowing for higher adsorption of the collector.

Effects of monohydric alcohols of varying chain lengths and isomeric structures on magnesite and dolomite flotation by dodecylamine

Monohydric alcohols with varying chain lengths and isomeric structures, which had significant effects on improving the magnesite and dolomite flotation, were added separately to replace part of dodecylamine (DDA). The intensified effects of alcohols differ with different chain lengths and isomeric structures. Alcohols can enhance the adsorption of DDA and reduce the adsorption distance of DDA on both surfaces of magnesite and dolomite. And the adsorption energy of the mixed collector decreased with the increasing chain length of alcohol. The isomeric alcohols presented more significant effects on lowering the adsorption energy of the collectors. The co-adsorption of alcohol compressed the hydration layer and dilute the water concentration in the hydration layer. Changes of the hydration layer were greater with adding alcohol with a long carbon chain and isomeric structure. Thus, alcohols with long chain lengths and isomeric structures performed better in improving the flotation of magnesite and dolomite.

Selective adsorption of a new depressant Na2ATP on dolomite: Implications for effective separation of magnesite from dolomite via froth flotation

Up to now, there is still a great challenge to efficiently separate magnesite from calcium-bearing carbonate minerals, especially dolomite, via froth flotation owing to their similar physicochemical properties. In this investigation, a novel depressant adenosine 5′-triphosphate disodium salt (Na2ATP) was introduced into the flotation process using the collector sodium oleate (NaOl), which was proved to be effective for the separation of dolomite and magnesite. The flotation results demonstrate that Na2ATP exhibits a more intense depression on the flotation of dolomite than that of magnesite and can separate effectively magnesite from dolomite, which depends on much less NaOl adsorption onto dolomite in the presence of Na2ATP. Zeta-potential detection and adsorption amount tests illustrate that the pre-addition of Na2ATP strongly interferes with the interaction between NaOl and dolomite so that a more significant reduction in adsorption of NaOl on the surface of dolomite in comparison with magnesite. Moreover, infrared spectral (IR) and X-ray photoelectron spectroscopy (XPS) measurements further confirm that the depressant Na2ATP is adsorbed more strongly onto dolomite than magnesite. And the selective adsorption of Na2ATP onto dolomite rather than magnesite was mainly due to the strong bonding of its phosphate groups and the calcium sites only exposed to the dolomite surface, resulting in selectively depressing the flotation of dolomite.

Improving flotation separation of apatite from dolomite using PAMS as a novel eco-friendly depressant

Froth flotation is widely used as an effective method for separating apatite from dolomite. However, it is of difficulty to realize the efficient separation of apatite and dolomite using the traditional fatty acid collectors without any depressants due to their similar physicochemical properties. In this work, the depression performance of poly (acrylic acid-co-maleic acid) sodium salt (PAMS) acting as a new depressant was evaluated via the flotation experiments, when sodium oleate (NaOl) was employed as the collector. The results from flotation experiments illustrated that PAMS effectively depressed the dolomite flotation whereas it exhibited weak influences on the floatability of apatite. It was also found that the reagent scheme of 14 mg/L PAMS and 100 mg/L NaOl could effectively remove dolomite from apatite at pH 9.00. Moreover, the adsorption mechanism of PAMS onto the two minerals was uncovered through the surface analyses. The analyzed results indicated that the interaction of PAMS with magnesium ions exposed to dolomite played a vital part in the selective adsorption of PAMS onto dolomite. Magnesium, as a major component of dolomite rather than apatite, enhanced the chemisorption of PAMS onto dolomite. Furthermore, the larger pre-adsorption of PAMS onto dolomite than apatite significantly led to the much less adsorption of NaOl on the dolomite surface, thereby reducing the hydrophobicity of dolomite in NaOl system and intensively depressing the dolomite flotation. Therefore, PAMS can be utilized as a potential depressant for removing dolomite from apatite by direct flotation.

Selective adsorption of a high-performance depressant onto dolomite causing effective flotation separation of magnesite from dolomite

This research focused on the adsorption features and depression mechanism of 1-hydroxyethylene-1,1-diphosphonic acid (HEDP) used as a novel dolomite depressant on dolomite and magnesite surfaces, to extend the application of HEDP for the selective flotation of magnesite from dolomite. The depression impacts of HEDP on the flotation behaviors of the two minerals were investigated through micro-flotation tests. The flotation results indicated that, when sodium oleate (NaOl) was used as the collector, HEDP displayed an outstanding depression effect on the dolomite flotation, whereas it had only a slight influence on the magnesite flotation. Dolomite and magnesite could be efficiently separated at approximately pH 10 with a reagent scheme of 200 mg/L HEDP and 120 mg/L NaOl. The selective depression mechanism of HEDP for dolomite was revealed using contact angle, X-ray photoelectron spectroscopy (XPS), zeta potential, and infrared spectrum (IR) analyses. The results from the contact angle tests indicated that HEDP selectively reduced the surface hydrophobicity of dolomite in the NaOl system. Besides, zeta-potential measurements and IR analyses revealed that the addition of HEDP prior to NaOl had no significant impact on the adsorption of NaOl onto magnesite; however, this addition strongly prevented NaOl from being adsorbed onto dolomite, resulting in a significant difference in the flotation performances of the two minerals. Furthermore, crystal chemistry calculations and XPS analyses confirmed that the strong adsorption of HEDP on the dolomite surface could be attributed to the interaction between the HEDP electron-rich groups and the calcium species exposed to dolomite. Thus, HEDP could be used as a high-performance depressant for the dolomite flotation to realize the decalcification of the magnesite flotation.

Study on the effect of collector and inhibitor acid on the floatability of collophane and dolomite in acidic media by TOF‐SIMS and XPS

Most of the phosphate ore in southern China is contained within siliceous dolomite phosphate rock, and more than 90% of it is medium and low‐grade collophane. Reverse flotation of carbonate gangue minerals (dolomite) from phosphate in acidic media is still the most economical method for the reduction of carbonate in collophane concentrates. It has been recognized that the collophane and dolomite in acidic media affect the surface properties of minerals, thereby affecting their flotation properties. In this paper, HCl and H3PO4 were used as regulators or inhibitors to study the flotation behaviour of collophane and dolomite. The inhibition mechanism of collophane and dolomite in two acid media was studied by time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) and X‐ray photoelectron spectroscopy (XPS) analyses. It was found that the addition of an inhibiting acid can partially depress the collophane and improve the flotation of dolomite, thus achieving their flotation separation, and the inhibition effect of H3PO4 on collophane is better than that of HCl. And it was found by TOF‐SIMS analysis that the increase in acid concentration did not reduce the adsorption concentration of the collector, and the main reason for the inhibition was not the decrease in the adsorption concentration of the collector. The adsorption capacity of collector on dolomite surface with H3PO4 is greater than that with HCl. The XPS test indicated that metaphosphate (PO3−1) is the pivotal ion for depressing collophane under acid conditions.

Promising Options for Solving the Dolomite Problem of the Florida Phosphate Resources—a Brief Review

Separation of dolomite from phosphate is the most challenging problem in phosphate mineral processing. Over 50% of the future phosphate reserve in Florida contains too much dolomite to process using the current industry practice. The current phosphoric acid production practice requires less than 1% MgO in the phosphate concentrate as the feed material. The Florida Industrial and Phosphate (FIPR) Institute has collaborated with worldwide experts in the field to address this issue. As a result, the industry is now offered three feasible options. Option 1 offers three methods for reducing MgO content in the concentrate from the Crago process, including adding a dolomite depressant in the rougher flotation step, dolomite flotation of the cleaner concentrate, and scrubbing the cleaner concentrate in quartz sand. These methods could reduce MgO content in the final concentrate by 20–40%. Option 2 involves crushing and grinding of high-dolomite phosphate pebbles followed by dolomite flotation at slightly acidic pH using a new collector that does not require phosphoric acid as a phosphate depressant, achieving a final concentrate analyzing less than 0.9% MgO at about 87% P2O5 recovery. Option 3 is a gravity separation technique using an innovative separation jig, and its full potential remains to be demonstrated.

Effect of Sodium Pyrophosphate on the Reverse Flotation of Dolomite from Apatite

In this study, the effect of sodium pyrophosphate (NaPP) on the separation of apatite from dolomite by flotation was systematically investigated. Flotation results revealed that NaPP could selectively depress the flotation of apatite, thus realizing the separation of apatite from dolomite. Further, the selective depression mechanism of NaPP was studied through zeta potential measurements, contact angle measurements, and X-ray photoelectron spectroscopy (XPS) analysis. The results demonstrated that the adsorption of sodium oleate (NaOL) onto apatite surface was depressed by the preferential interaction of NaPP with active Ca sites. For dolomite, while the presence of NaPP hindered the interaction of NaOL with active Ca sites, it appeared to enhance the reactivity with active Mg sites. Thus, the adsorption of NaOL onto dolomite surface was hardly influenced. In this way, the separation of apatite from dolomite was achieved.

Application of New Flotation Machine on Phosphate Flotation

Phosphate is a typical oxide ore characterizing that generating abundant froth during flotation. In this research a new flotation machine was employed in the flotation of phosphate. Comparing to regular flotation machine, in the reverse flotation of dolomite the recovery and grade of MgO has no significance improvement. While, in the case of reverse flotation of silicon dioxide, the new flotation machine has significance advantage. In 5 minutes of flotation time, the yield of froth is 20.66% with new machine, which equals to yield using regular machine under 8 minutes. The flotation time has been shorten by new machine. In addition, the recovery of silicon dioxide improved by 6% and the grade of silicon dioxide in phosphate concentrate decreased by 1.3% comparing the regular flotation machine. The results demonstrate that new flotation machine is more suitable and efficient for phosphate flotation

Mechanisms involved in reactive flotation of dolomite

Dolomite impurities are increasing in the currently mined phosphate deposits in Florida. Several research efforts have been conducted in various laboratories around the globe to find methods to economically removing the dolomite. However, a universal and cost-effective process is not now in commercial use. In this paper, a new process for dolomite/apatite separation is presented. The differential solubility of dolomite in slightly acidic solution is utilized to generate micro CO2 bubbles at the dolomite/water interface. Particle (dolomite)/bubble aggregates float to the surface leaving phosphate concentrate with low MgO content. Interestingly, up to 6.0 mm particles can be floated by such micro-bubble/particle aggregates. Different surface-active agents were tested to stabilize the bubbles. Results of these tests are presented, and the mechanisms involved are discussed.

Statistical significance of some operating parameters on dolomite removal from phosphate using amphoteric collector

An amphoteric collector was tested for dolomite removal from phosphate ore. The effects of some operating parameters and their significance on the flotation of dolomite were studied using statistically designed experiments. The parameters studied were impeller speed, pH and collector dosage. Analysis of the results showed that pH is the most significant parameter. Moreover, a concentrate containing 0.53% MgO and ≈31.1% P2O5 with a recovery of ≈ 90% can be achieved at optimum values of studied parameters, i.e., a pH of 12, an impeller speed of 1,000 rpm and a collector dosage of 2.5 kg/t.

Processing Florida dolomitic phosphate pebble in a double reverse fine flotation process

A double reverse fine flotation process was employed to process Florida high-dolomitic phosphate pebbles. In this study, the dolomitic phosphate pebble sample was ground to −150 μm (100 mesh) for liberating the phosphate to achieve the maximum phosphate grade and recovery. The selective fatty-acid-type collector for dolomite and H3PO4/H2SO4, in the ratio of 2:1, as both phosphate depressant and pH modifier, were used to effectively float dolomite at pH 5 to 5.5. The dolomite flotation sink product, rich in phosphate, was sized at 37 μm (400 mesh). The oversized fraction was further subjected to a siliceous flotation using a fatty-acid amine collector to reject silica. The amine flotation sink product was combined with the undersized fraction of dolomite flotation sink product to form a composite phosphate concentrate. The final composite phosphate concentrate had the grade of 31.6% P2O5 and 0.8% MgO, with a 92% P2O5 recovery, from the fine feed containing 26.7% P2O5 and 2.2% MgO. The effects of pH and reagent dosages on the efficiency of dolomite separation were studied. Two fatty-acid-type collectors were evaluated by flotation rates. This double reverse fine flotation process was also used effectively in processing Florida high dolomitic phosphate pebble samples obtained from various locations.