The tantalum and niobium ore beneficiation and roughing generally adopts the gravity separation method, and the selection adopts the gravity separation, flotation, electromagnetic separation or combined process of beneficiation and smelting. To deal with ores with high content of powder or primary mud, the washing operation is essential. High-efficiency grinding and grading equipment to reduce sliming of tantalum and niobium minerals.

Commonly used collectors for tantalum-niobium flotation include fatty acids, arsine acids, phosphonic acids, hydroxamic acids, and cationic collectors. With the development of the chemical industry, there will be a wide range of raw material sources, a simple synthesis process, easy biodegradation, good selectivity, non-toxic and harmless, and reasonably priced agents will continue to appear to meet the needs of tantalum and niobium concentrators.1. Mineral technology characteristics of tantalum-niobium ore

The general chemical formula of niobite-tantalite is AB2O6, and the two are referred to as niobium tantalite. A is iron and manganese, and B is niobium and tantalum. The different forms, from pure niobium to tantalum, have a range of isomorphous structures characterized by variable ratios of iron and manganese. It contains Nb2O5 1.97~78.88%, Ta2O5 5.56~83.57%, MnO 1.26~16.25%, FeO 1.89~16.25%. There are also isomorphic mixtures such as Ti, Zr, W, TR, and U. If niobium is in the majority, the mineral is called niobite, and if tantalum is in the majority, it is called tantalite. The crystal lattice of the mineral is an orthorhombic structure, and the space group symbol is Pcan. The structure consists of layers of A and B octahedra. Identical octahedrons are connected in layers by edges to form chains and then connected to common vertices. An A octahedral layer is connected to the adjacent B octahedral layer from two sides through a vertex to form a BAB structure.

The lattice parameters of many minerals of niobite-tantalite are related to the composition of the sample, and their fluctuation ranges are as follows: a=0.5133~0.5054nm; b=1.445~1.405nm; c=0.5762~0.5683nm. The atomic spacing in niobium-tantalum manganese ore: Mn-O=2.12~2.14 angstroms, Ta-O=1.86~2.12 angstroms. Mineral colors are black, brown-black and reddish-brown. The Mohs hardness is: niobite 4.3~6.5; tantalite 6.5~7.2. The microhardness value of niobite is 2400~8000MPa, and that of tantalite is 8000~10700Mpa.

The magnetic susceptibility of niobite-tantalite is (22.1~37.2)×10-6. The dielectric coefficient of niobite is 10~12, and that of tantalite is 7~8. The density of the mineral is 5.15~8.20 (increases with the content of tantalum).2. The beneficiation technology of tantalum and niobium ore

The tantalum-niobium ore beneficiation generally adopts gravity separation to discard most of the gangue minerals to obtain low-grade mixed rough concentrate. Various beneficiation methods such as gravity separation, flotation, electromagnetic separation or combined beneficiation and smelting process are used for selection, so as to achieve the separation of various useful minerals.

2.1 Foreign tantalum and niobium beneficiation

When dealing with fine ores with high content of primary mud, washing operation is essential. The weathered pegmatite alluvial clay roughing plant in Greenbush Mine, Australia, is equipped with two washing systems. The clay balls enter the self-grinding machine to grind about 4mm, and then sieve with a cylindrical sieve with an aperture of 10mm. The materials under the sieve are selected, and the materials on the sieve are discarded or returned for regrinding. The water consumption for ore washing is 5m3/t, and the processing capacity of the cylindrical screen reaches 350 tons/hour.......... Taiwan.

Foreign tantalum and niobium concentrators attach great importance to the use of high-efficiency grinding and grading equipment to reduce the sliming of tantalum and niobium minerals. The primary pegmatite roughing plant of the Greenbush Mine used the peripheral discharge rod mill and the vibrating screen closed circuit to achieve good results. The Bernick Lake tantalum mine in Canada has been continuously improved, and the grinding process currently used is very distinctive. The mine uses a Ф2.4m×3.6m Massey-type grid ball mill AC horizontal vibrating screen (linear screen) closed circuit, the sieving particle size is 2.5mm, and the sieve is classified by 0.2mm with a Derek sieve, -2.5+0.2mm particles The grade is classified by a spiral concentrator, and the tailings are dewatered by an arc screen and then returned to be ground again. The ball mill has two kinds of products to form a cycle, that is, one mill is used to realize two-stage closed-circuit grinding. The cyclic load rate of the grinding circuit is usually about 180% after adjustment, and it is easy to cause over-grinding if the cyclic load is small.

The roughing of tantalum-niobium iron ore in foreign countries is still dominated by gravity separation, and high-efficiency gravity separation equipment is often used, and the process is simple. For example, Greenbush Mine directly uses jig for roughing of -10mm raw ore. The gravity separation-flotation-gravity separation process formed in the 1980s at the Bernick Lake tantalum mine in Canada is becoming more and more perfect. The process is still dominated by gravity separation, and flotation is only used to treat fine mud. The gravity separation equipment uses GEC spiral concentrator, 3-layer suspended Dyster shaker, Holman mud shaker, and cross-flow belt concentrator. In the former Soviet Union, flotation was used to separate tantalite, fine spar and topaz in the gravity concentrate. The collector was hydroxamic acid, and the regulator was oxalic acid. In hydrochloric acid medium (pH2) flotation, when feeding ore When the content of Ta2O5 is 2.52%, the concentrate grade is 27% and the recovery rate is 90%.

The beneficiation method of pyrochlore ore mainly adopts flotation method. In order to improve the quality of concentrate and reduce the consumption of chemicals, the pyrochlore beneficiation process has strengthened the operations of desliming, iron removal, desulfurization, phosphorus, lead and barium in recent years. Neobeck pyrochlore ore -0.2mm was selected as raw ore with a cyclone to remove -10μm slime, and sorted according to the mud and sand. First, apatite and carbonate minerals were flotated with fatty acid collectors, then magnetic separation was carried out to remove iron, and then pyrochlore was flotated with amine collectors, and finally pyrite flotation was carried out on the pyrochlore concentrate. and hydrochloric acid leaching to reduce sulfur, phosphorus and carbonate mineral content. When the raw ore contains 0.6%~0.7% Nb2O5, the final concentrate grade is 58%~62%, and the recovery rate is 60%~65%.2.2 Domestic tantalum and niobium beneficiation

2.2.1. Tantalum-niobium ore roughing

Domestic tantalum-niobium ores are generally of low grade, and their minerals are brittle and dense. In order to ensure the grinding particle size and avoid over-grinding, the stage grinding stage separation process is generally adopted. Jiangxi Yichun Tantalum and Niobium Concentrator adopts lateral arc screen instead of linear vibrating screen for screening. The results of on-site exploration test show that the fineness of the upper screen can be reduced by 14.70%, the thickness of the underscreen can be reduced by 4.3%, and the screening efficiency can be improved by 17.72% %. The successful test of the equipment provides a new way for the transformation of the first stage of grinding and screening on site. Nanping, Fujian is a large-scale granite pegmatite deposit. In 1998, we conducted a beneficiation test study on the ore to provide a design basis for the construction of the plant. Don't craft. The first section uses a rod mill and forms a closed circuit with a sieve to reduce over-grinding. The second-stage grinding adopts a ball mill and forms a closed circuit with a high-frequency vibrating fine screen. In addition to strictly controlling the particle size, it can also increase the processing capacity and improve the grinding efficiency. The ore roughing adopts a single gravity separation process. The gravity separation equipment includes GL spiral concentrator, spiral chute and shaking table. The selected raw ore contains (TaNb)2O5 0.0499%, Sn 0.0598%, the rough concentrate obtained after roughing is 0.248%, contains (TaNb)2O5 14.94% (including Ta2O5 10.79%), and the recovery rate of the raw ore is 0.248%. 74.30% (Ta2O5 recovery rate is 74.96%); with Sn 15.71%, the recovery rate of raw ore is 65.11%.

2.2.2. Selection of tantalum and niobium ore

The rough concentrate obtained by the roughing process is generally mixed rough concentrate, which needs to be further selected to separate out a variety of useful minerals. The mineral composition of the rough concentrate is different, and the separation methods used are also different. Generally, a combination of methods is used. For example, the selection of tantalum and niobium in Nanping, Fujian adopts a combination of magnetic-heavy-floating. First, use 6% hydrochloric acid solution to clean the mineral surface, then use weak magnetic separation to remove strong magnetic minerals and iron filings, dry and sieve into +0.2, +0.1 and -0.1mm three grades, respectively use a dry magnetic separator to obtain tantalum and niobium concentrate through one roughing and one sweeping separation. The selected concentrate is subjected to flotation to remove sulfide ore to obtain tin concentrate. Selection results: the tantalum and niobium concentrate rate is 0.0764%, containing (TaNb)2O5 45.64% (Ta2O5 32.57%), the recovery rate of raw ore is 69.92% (Ta2O5 recovery rate is 69.071%), and the recovery rate of selection operation is 94.11%; tin concentrate The recovery rate is 0.0581%, containing Sn60.25%, the recovery rate of raw ore is 58.49%, and the recovery rate of selection operation is 89.84%.

2.2.3. Flotation of fine-grained tantalum-niobium ore

The No. 69 ore body in the Dajishan tungsten deposit in Jiangxi Province is a large tantalum-niobium-tungsten-tungsten granite ore body. The main useful minerals in this ore are wolframite, scheelite, tantalum-niobite and fine spar, and useful minerals are embedded. The particle size is very fine, most of the particle size is 40~74μm, so the conventional gravity separation method is used, and the recovery rate of ore dressing is low, and the recovery rate of tantalum is only 25%~33%. Guangzhou Nonferrous Metal Research Institute adopts the combined heavy-flotation process to recover tantalum, niobium and associated tungsten minerals. When flotation feeds WO3 0.088% and Ta2O5 0.0145%, the flotation concentrate rate is 0.7%, and the concentrate contains WO3 10.84%. , Ta2O51.8%, the recovery rates of tungsten and tantalum are 85% and 87% respectively, and the enrichment ratio of concentrate is more than 100 times. Then re-selection enrichment, hydrometallurgical separation of tantalum and tungsten. The recovery rate of tantalum dressing and smelting reaches 44%.

The ore properties of the Bayan Obo Mine in Baotou are very complex. In particular, niobium minerals are famous for their lean, fine and miscellaneous beneficiation. Although the current beneficiation technology has made great progress compared with the past, the recovery rate of rare earth beneficiation is still low. The beneficiation recovery is still in the research stage. Guangzhou Institute of Nonferrous Metals uses flotation method to enrich niobium minerals from rare earth flotation tailings, using Pb(NO3)2 as activator, D-1 as calcium mineral inhibitor, and a combination of hydroxamic acid as the main trapping agent. Collecting agent, carry out niobium flotation in pH6 medium, after flotation-enriched niobium coarse concentrate is desulfurized, it is selected by weak magnetic-shaking table process to obtain rich niobium iron concentrate and iron concentrate. The rich niobium iron concentrate 1 contains 1.66% Nb2O5, the concentrate 2 contains 0.59% Nb2O5, and the total recovery rate of niobium is 35.58%. After studying the rare earth flotation tailings in Bayan Obo Mine, Chen Quanyuan et al. proposed that after the rare earth flotation tailings are concentrated and deslimed, oxide paraffin soap, water glass anti-flotation fluorite and residual rare earth minerals are added, and the products in the tank are concentrated. Then, add ammonium fluorosilicate and paraffin soap to flotate iron minerals to obtain iron concentrate, and add sulfuric acid, carboxymethyl cellulose, salicylic hydroxamic acid, C5-9 hydroxamic acid and oxalic acid to the iron tailings. The niobium flotation concentrate containing 1.67% of Nb2O5 and the recovery rate of 40.14% was obtained by roughing and three-time beneficiation. The concentrate was then subjected to strong magnetism to separate iron and niobium to obtain niobium concentrate of non-magnetic products and niobium secondary of magnetic products. concentrate. In addition, the magnetic-levitation process can also obtain rare earth foam products and iron ore concentrates.3 Research status and progress of tantalum-niobium ore flotation reagents

The mineral resources of tantalum and niobium are famous for their poor, fine and miscellaneous beneficiation. Although the current beneficiation technology has made great progress compared with the past, the beneficiation recovery rate is still low. In recent years, many scholars at home and abroad have carried out a lot of research work on the flotation reagents of tantalum and niobium. Among them, the more effective collectors are fatty acids, arsine acids, phosphonic acids, hydroxamic acids, and cationic collectors. .

3.1. Tantalum and Niobium Mineral Collectors

(1) Fatty acid collectors. In 1959, the former Soviet Union Polykin С И and Gladkikh Ю А used oxide mineral collectors: oleic acid, sodium oleate, sodium tridecanoate, sodium alkyl sulfate and sodium isooctyl phosphate. Floatability of niobate-tantalite, tourmaline and garnet. Experiments show that when fatty acid is used as collector, the collecting ability of saturated hydrocarbon group is worse than that of unsaturated one. When the pH value is 6~8, the flotation of niobate-tantalite with sodium oleate is very effective, and it is inhibited in strong acid medium and strong alkaline medium.

Modification of fatty acids can improve their selective capture. For example, new effective active groups such as sulfonic acid group, polycarboxyl group, sulfuric acid group, halogen, amine (amino) group, aminoacyl group and amide group are introduced into the molecule.

(2) Arsinic acid collectors. Arsinic acid can form strong surface compounds with rare metal minerals such as tantalum and niobium, and the hydrocarbon groups are outward, making the minerals hydrophobic. However, there is no such chemical adsorption with gangue minerals, so the collection ability is strong and the selectivity is good. The disadvantage is that there are pollution problems in the production and use of arsine-containing substances. Benzylarsinic acid and toluarsinic acid are effective collectors for tantalum-niobium minerals, wolframite and cassiterite. Mixing arsinic acid with xanthate can greatly improve the recovery rate of wolframite and cassiterite, and can also improve tantalum-niobium minerals. Recovery rate.

(3) Phosphonic acid scavengers. The solubility of phosphonic acid in aqueous solution changes with the change of pH value. Generally, it has good solubility in alkaline medium. In fact, it is dissolved by the formation of alkali metal salts. Phosphonic acid and Ca2+, Fe2+, Fe3+, Sn2+ and other metal ions form insoluble salts, so it can capture tantalum and niobium minerals. The research on collecting ferroniobium rutile with bisphosphonic acid shows that when the pH value of the slurry is 2~4, bisphosphonic acid is a good collector of ferroniobium rutile, and its recovery rate reaches 90.87%~91.70%. The acid is adsorbed on the surface of ferroniobium rutile, and the adsorption form is mainly chemical adsorption.

(4) Hydroxamic acid collectors. Hydroxamic acid and its salts were used for flotation of malachite and hematite in the early days, and later used as collectors for various rare metal ores. Naphthalene hydroxamic acid has good selective collection performance for wolframite, but very weak collection ability for quartz and fluorite. C7~9 hydroxamic acid is used for flotation of yellow greenite ore, the concentrate contains Nb2O5 6~20%, and the recovery rate is 65~66%. A tantalum and niobium fine mud ore in a certain place in my country uses industrial hydroxamic acid and transformer oil for rough separation. When the feed ore contains 0.094% Nb2O5, the crude concentrate grade Nb2O5 0.9~1.0% can be obtained, and the recovery rate is about 90%.

(5) Cationic collectors. In neutral medium, cationic collectors are effective collectors for tantalum-niobium minerals; in strong acid medium, the surface of tantalum-niobium minerals is mostly positively charged, which is not conducive to the flotation of cationic collectors;

From the point of view of solution chemistry, cationic collectors undergo hydrolysis reaction in aqueous solution. In strong alkaline medium, high OH-concentration is not conducive to the hydrolysis reaction, and the cationic concentration of collectors is reduced, which is unfavorable for flotation. Brazil's Araxa processing plant uses amines as collectors, and the flotation of pyrochlore has achieved good results. Another study shows that ammonium lauryl acetate can effectively flotate niobate minerals in neutral medium.

(6) Other collectors. The research on the collection performance of tantalum-niobium minerals by using the new agent N2 shows that N2 with high carbon chain is an effective collector of tantalum-niobium minerals, and the adsorption on the surface of tantalum-niobium minerals is chemical adsorption. Flotation of Bayan Obo niobium ore with N-nitrosophenylhydroxylamine has achieved good results. The exploratory test of the former Soviet Union Berger Γ С shows that the hydrocarbyl sulfate is also suitable for the flotation of niobate-tantalite in pegmatite deposits.

Many flotation agents, especially collectors, are not very effective when used alone, but when some agents are used in combination in a certain proportion, the effect is not a simple additive effect, but a synergistic effect, that is, 1 +1>2 synergy. For example, xanthate and hydroxamic acid are combined for flotation of copper oxide; sodium oleate and hydroxamic acid are combined for flotation of andalusite; Mixed use of Tal soap, flotation of wolframite fine mud; F203 and salicylic hydroxamic acid mixed with flotation of cassiterite fine mud have achieved good results.1. Tantalum-niobium ore flotation regulator

The main gangue minerals of tantalum niobium are silicate minerals, fluorite and carbonate minerals. Typical inhibitors of these minerals are water glass, sodium hexametaphosphate, starch, pyrophosphoric acid, sodium hydrogen phosphate, sodium lignosulfonate, tannins, lactic acid, citric acid, tartaric acid, and the like. The pH value has a great influence on the flotation process of tantalum and niobium, and the regulators commonly used to adjust the pH value are sulfuric acid, hydrochloric acid, sodium hydroxide, soda, etc.

2. Analysis of existing problems in flotation of tantalum-niobium ore

(1) The problem of the collector's ability to collect. The molecules containing functional groups -COOH, -SO4H, -SO3H have strong collecting ability and poor selectivity, and are only suitable for flotation of tantalum-niobium fine mud with simple mineral composition and quartz as the main gangue. The ability of hydroxamic acid to collect tantalum-niobium fine mud is weaker than that of fatty acid, but it is better to choose. Phosphonic acid has a relatively strong ability to collect tantalum-niobium ore, but is sensitive to Fe2+ and Ca2+ ions. have a greater impact on the flotation process.

(2) The environmental pollution of collectors and the cost of chemicals. Arsonic acid can form strong surface compounds with metal minerals such as tantalum and niobium, and the hydrocarbon groups are outward, making the minerals hydrophobic, and there is no such chemical adsorption with gangue minerals, so the collection ability and selectivity are strong. It is insensitive to Ca2+ and Mg2+ ions, and has strong adaptability to ores with high calcite content. However, arsine acid is highly toxic and may cause environmental pollution. The modifier sodium fluorosilicate or sodium fluoride used in conjunction with phosphonic acid and sulfosuccinic acid also has certain toxicity. In the flotation of tantalum and niobium fine mud, the dosage of chemicals used is large and the price is high; at the same time, some chemicals are more toxic, which requires increased environmental protection costs, thereby increasing the cost of beneficiation. When using hydroxamic acid flotation, the effect is better, but the dosage is larger.

In recent years, many scholars at home and abroad have done a lot of work in the selection and development of tantalum-niobium flotation reagents, and found many collectors with good selectivity. Although some progress has been made in the research of tantalum and niobium flotation reagents, due to the high price of reagents, only a few foreign niobium mines have adopted flotation methods, such as Canada Oka Concentrator and Brazil Araksa Mine. With the development of more and more refractory tantalum and niobium resources, it is expected that the demand for tantalum and niobium beneficiation agents with good selectivity and reasonable price will continue to increase.