Mineral Processing

Niobium-Tantalum Ore Beneficiation

This post is original posted on JXSC Mining’s Engineering Blog

Tantalum and niobium ore beneficiation coarse separation is usually used the gravity separation method, also, the flotation, electromagnetic selection and electrometallurgical separation are used in a combined process, when dealing with powder or primary mud content of ore, washing and scrubber operations are essential, while the use of high-efficiency grinding and classification equipment to reduce the mud of tantalum and niobium minerals. 

In flotation processing, the commonly used trapping agents for tantalum-niobium flotation are fatty acids, arsenical acids, phosphonic acids, hydroxamic acids, cationic trapping agents, etc. And something you should specially focus on is environmental pollution of trapping agents and the cost of pharmaceuticals.

Characteristic of Tantalum-niobium minerals

The chemical formula of niobium-iron ore-tantalite is AB2O6, both of which are referred to as niobium-tantalum. Where A in the formula stands for iron and manganese, and B stands for niobium and tantalum

The magnetization rate of niobium-iron ore-tantalite is (22.1 to 37.2) × 10-6. The dielectric coefficient of niobium-iron ore is 10 to 12, and tantalite is 7 to 8. The density of the mineral is 5.15 to 8.20 (increases with the increase of tantalum content).

Tantalum-niobium ore beneficiation technology

Tantalum and niobium ore beneficiation generally uses gravity separation to discard most of the vein minerals and obtain a low-grade mixed crude concentrate, and the mineral composition of the crude concentrate entering the selection operation is complex, generally containing a variety of useful minerals, which is difficult to sort, and usually uses a variety of beneficiation methods such as gravity separation, flotation, electromagnetic selection or combined electrometallurgical process for selection, so as to achieve the separation of a variety of useful minerals.

General tantalum-niobium beneficiation process

Washing operations are essential for processing ores with a high content of fines or primary mud. Australia Greenbus mine weathered pegmatite alluvial clay coarse separation plant, with two washing systems, the raw ore with a diameter of 1.5m, aperture 10mm cylindrical sieve twice after washing, sieve down into the selection, sieve on the large pieces and clay balls into the self-mill grinding about 4mm, and then aperture 10mm cylindrical sieve screening, sieve down into the selection of materials, sieve on the material discarded or returned to re-mill. Washing water consumption of 5m3 / t, cylinder sieve capacity of 350 tons / hour – set.

International tantalum-niobium processing plants attach importance to the use of high-efficiency grinding and classifying equipment to reduce the mudification of tantalum-niobium minerals. 

For example, the Greenbus mine primary pegmatite roughing plant with peripheral discharge rod mill and vibrating screen closed circuit to achieve better results. Canada’s Lake Bernicke tantalum mine by continuous improvement, the current use of the grinding process is very distinctive. The mine with a Ф2.4m × 3.6m Masi type lattice ball mill A-C horizontal vibrating screen (linear sieve) closed circuit, sieve size 2.5mm, under the sieve with Drake sieve by 0.2mm classification, -2.5 + 0.2mm particle size with spiral concentrator separation, its tailings by the arc sieve dewatering back to re-mill. The ball mill has two products constituting the cycle, i.e. one mill is used to achieve two closed circuit grinding. The grinding circuit is usually adjusted to a cycle load rate of about 180%, with a small cycle load prone to the formation of over-crushing.

At present, the international roughing of tantalum-niobium iron ore is still dominated by gravity separation, and more efficient gravity separation equipment with a simple process. For example, the Greenbosch Mine uses jigger directly for roughing of -10mm raw ore. The process of gravity separation-flotation-gravity separation formed in the 1980s in Canada’s Bernicke Lake tantalum mine is becoming more and more perfect, and the process is still mainly based on gravity separation, and flotation is only used to deal with fine mud. The gravity separation equipment mainly adopts spiral concentrator, 3-layer suspended Dexter shaker, Holman mud shaker, cross-flow belt concentrator.

Flotation was once used in the Soviet period to separate tantalite, fine crystals and topaz in the gravity separation concentrate, the trapping agent was isohydroxamic acid, the adjusting agent was oxalic acid, flotation in hydrochloric acid medium (pH=2), when the feed contains Ta2O52.52%, the concentrate grade is 27%, the recovery rate is 90%.

Some tantalum-niobium beneficiation practices from China

Tantalum-niobium ore coarse beneficiation

The raw grade of domestic tantalum-niobium ore in China is generally very low, and its minerals are brittle and dense. In order to ensure the grinding size and avoid over-crushing, the stage grinding stage beneficiation process is generally used.

Jiangxi Yichun tantalum-niobium beneficiation plant uses a lateral arc screen to replace the linear vibrating screen for screening, and the results of the field exploration test show that: the screen can reduce 14.70% of the fine pinch, the screen can reduce 4.3% of the coarse pinch, and the screening efficiency can be increased by 17.72%. The successful test of this equipment provides a new way for the transformation of a section of the grinding screen on site. Fujian Nanping is a large granite pegmatite deposit, in 1998 by the Guangzhou Institute of Non-ferrous Metals on the ore beneficiation test research, to provide design basis for the construction of the plant, according to the tantalum niobium and cassiterite mineral size embedding characteristics, proposed the use of stage grinding, stage separation process. A rod mill is used in the first stage and forms a closed circuit with the screen to reduce over-crushing. The second stage grinding adopts ball mill and forms a closed circuit with high frequency vibrating fine screen, which can increase the processing capacity and improve the grinding efficiency in addition to strictly controlling the particle size. The mine uses a single gravity separation process for roughing. The gravity separation equipment has GL spiral concentrator, spiral chute and shaking table. The mine into the original ore containing (TaNb)2O50.0499%, Sn0.0598%, after roughing to obtain the coarse concentrate mineral rate of 0.248%, containing (TaNb)2O514.94% (of which Ta2O5510.79%), the recovery of the original ore 74.30% (Ta2O5 recovery of 74.96%); containing Sn15.71%, the recovery of the original ore Recovery rate of 65.11%

Tantalum-niobium ore selection

The crude concentrate obtained from the roughing process is generally a mixed crude concentrate, which needs to be further selected to separate a variety of useful minerals. Such as tantalum niobium selection in Nanping, Fujian Province, the first 6% hydrochloric acid solution to clean the surface of the mineral, and then weak magnetic separation to remove the strong magnetic minerals and iron filings, drying and sieving into +0.2, +0.1 and -0.1mm three levels, respectively, with a dry strong magnetic separator by a roughing, a sweeping tantalum niobium concentrate, selection results: tantalum niobium concentrate rate of 0.0764%, containing (TaNb)2O545.64% ( Ta2O532.57%), recovery of 69.92% to the original ore (Ta2O5 recovery 69.071%), recovery of 94.11% for the selection operation

Flotation of fine-grained tantalum-niobium ore

Jiangxi Dajishan tungsten ore body No. 69 is a large tantalum-niobium-bearing tungsten granite ore body, the tantalum-niobium-iron minerals in this ore are embedded in a very fine particle size, most of the particle size is 40-74μm, so using the conventional gravity separation method, the beneficiation recovery is low, and the tantalum recovery is only 25%~33%.

Guangzhou Institute of Non-Ferrous Metals uses a combined heavy-flotation process to recover tantalum-niobium minerals, in flotation feed Ta2O50.0145%, the flotation concentrate rate is 0.7%, the concentrate contains Ta2O51.8%, tantalum recovery of 87%, the concentrate enrichment ratio is more than 100 times. Then gravity separation enrichment and hydrometallurgical separation of tantalum and tungsten. It makes the electrometallurgical recovery of tantalum reach 44%.

Baotou Baiyun Ebo ore is very complex in nature, especially niobium minerals to poor, fine, miscellaneous difficult to select, Guangzhou Institute of non-ferrous metals flotation method of rare earth flotation tailings for niobium mineral enrichment, using Pb (NO3) 2 as activator, D-1 as inhibitor of calcium minerals, hydroxamic acid-based combination of trap, niobium flotation in a pH 6 medium, by flotation enrichment of niobium crude concentrate desulfurization After flotation, the niobium-rich iron concentrate and iron concentrate were selected using a weak magnetic-shaking process. Niobium-rich iron concentrate 1 contained 51.66% Nb2O and concentrate 2 contained 50.59% Nb2O, with a total recovery of 35.58% niobium.

After the study of rare earth flotation tailings from Baiyun Ebo mine by Chen Quangyuan et al. proposed that after the concentration and desliming of the rare earth flotation tailings, the addition of oxidized paraffin soap, water glass reverse flotation of fluorite and residual rare earth minerals, the concentration of the product in the tank, the addition of ammonium fluorosilicate, oxidized paraffin soap flotation of iron minerals to obtain iron concentrates, iron beneficiation tailings with sulfuric acid, carboxymethyl cellulose, salicylic hydroxamic acid, C5-9 hydroxamic acid and oxalic acid, after one roughing and Three selections to obtain a niobium flotation concentrate containing 51.67% Nb2O with a recovery of 40.14%, which is then subjected to strong magnetic separation of iron and niobium to obtain a niobium concentrate of non-magnetic products and a niobium sub-concentrate of magnetic products.

Research status and progress of flotation chemicals for tantalum-niobium ore

Tantalum-niobium mineral trapping agent

Tantalum niobium ore more effective trapping agents are fatty acids, arsenical acids, phosphonic acids, hydroxamic acids, cationic trapping agents.

1, fatty acid class trapping agent in the former Soviet Union, Poliquin and Gladkirch two people have used oxidized ore trapping agent: oleic acid, sodium oleate, sodium tridecanoate, sodium alkyl sulfate and sodium isooctyl phosphate detailed study of niobium-iron ore – tantalite floatability. Tests have shown that: when using fatty acids as trapping agents, the trapping ability of saturated hydrocarbon groups is worse than unsaturated ones. Flotation of niobium iron ore-tantalite with sodium oleate was extremely effective when the pH was 6-8, and was inhibited in both strongly acidic and strongly alkaline media. Modification of fatty acids can improve their selective catchability. For example, the introduction of new effective active groups sulfonic acid group, polycarboxyl group, sulfate group, halogen, amine (ammonia) group, amino acyl group and amide group in the molecule.

2, arsenate trapping agent arsenate can form a solid surface compound with tantalum, niobium and other rare metal minerals, hydrocarbon group outward, making the mineral hydrophobic. However, there is no such chemical adsorption with vein minerals, so the trapping ability is strong and selective. The disadvantage is that arsine-containing substances have pollution problems in both production and use. Benzyl arsenate and toluene arsenate is an effective trapping agent for tantalum-niobium minerals, arsenate mixed with yellow medicine can greatly improve the recovery of tantalum-niobium minerals.

3, phosphonic acid class trapping agent with bisphosphonic acid trapping niobium-iron rutile research shows that: in the pulp pH 2 ~ 4, bisphosphonic acid is a good trapping agent for niobium-iron rutile, its recovery rate of 90.87% to 91.70%, and that bisphosphonic acid is adsorbed on the surface of niobium-iron rutile, the adsorption form is mainly chemisorption.

4, hydroxamic acid class trapping agent tantalum niobium fine mud ore in one part of China with industrial iso hydroxamic acid with transformer oil for roughing, when the feed ore containing Nb2O50.094%, can get crude concentrate grade Nb2O50.9 ~ 1.0%, recovery rate of about 90%.

5, cationic trapping agent research shows that dodecyl amine acetate in neutral media can effectively flotation of niobium iron ore minerals.

6, other trapping agents using the new agent N2 on tantalum-niobium minerals trapping performance studies show that the high carbon chain of N2 is an effective trapping agent for tantalum-niobium minerals. The use of N-nitrosamine flotation of niobium ore in Baiyun Ebo achieved better results. Exploratory tests in the former Soviet Union showed that hydrocarbon sulfate is also adapted to the flotation of niobium-iron-tantalite in pegmatite deposits. Many flotation agents, especially the trapping agent, when used alone, the effect is less than ideal, but when certain agents are used in a certain proportion of the combination, the effect is not a simple sum effect, but a synergistic effect, that is, 1 + 1 > 2 synergistic effect. Such as yellow medicine and hydroxamic acid combination flotation of copper oxide; sodium oleate and hydroxamic acid combination flotation of red pillar; arsenical acid mixed with yellow medicine, copper and iron spirit mixed with benzol hydroxamic acid, benzol hydroxamic acid mixed with Tal soap, flotation of wolfram fine mud; F2O3 mixed with salicyl oxime acid flotation of cassiterite fine mud have achieved better results.

Tantalum-niobium ore flotation adjuster

The main vein minerals of tantalum-niobium ore are silicate minerals, fluorite and carbonate minerals. Typical inhibitors of these minerals are water glass, sodium hexametaphosphate, starch, pyrophosphate, sodium hydrogen phosphate, sodium lignosulfonate, tannin, lactic acid, citric acid, tartaric acid, etc. The pH value has a large impact on the tantalum-niobium flotation process, and the adjusting agents commonly used to adjust the pH value are sulfuric acid, hydrochloric acid, sodium hydroxide, soda, etc.

Analysis of tantalum-niobium ore flotation problems

1, the catchability of the trapping agent problem.

Molecular containing functional groups – COOH, – SO4H, – SO3H strong capture ability, poor selectivity, only for flotation of tantalum-niobium fine mud with simple mineral composition, quartz as the main vein. Hydroxamic acid has a weaker trapping capacity than fatty acid for tantalum-niobium fine mud, but has better selection. Phosphonic acid has a stronger trapping capacity for tantalum-niobium ore.

2, environmental pollution of the trapping agent and the cost of the agent.

Arsenous acid can form a solid surface compound with tantalum, niobium and other metal ores, hydrocarbon group outward, making the minerals hydrophobic, while there is no such chemical adsorption with vein minerals, so the trapping ability is strong and selective, while arsenous acid is insensitive to Ca2+ and Mg2+ ions, and is highly adaptable to ores containing high calcite. However, arsenious acid has high toxicity and may cause environmental pollution. In the flotation of tantalum-niobium fine mud, the amount of drug used is large and the price is high; at the same time, some agents are more toxic and need to increase the environmental protection cost, thus making the cost of mineral processing rise. When using hydroxamic acid flotation, the effect is better, but the dosage of pharmaceuticals is larger.

In recent years, the domestic tantalum and niobium flotation agent research has made some progress, but because the price of the agent is too high, only a few foreign niobium mines using flotation methods, such as Canada’s Oka beneficiation plant, Brazil’s Alaksa mine.