DD262845A1 - PROCESS FOR THE EXCLUSION OF BASTNAESITE CONCENTRATES - Google Patents

Abstract

The invention relates to the digestion of Bastnaesit concentrates with 25-38% SE2O3 and greater levels of minor minerals such as barite, fluorite, calcite, iron and manganese ores. According to the invention, the bastnaesite concentrates are reacted with concentrated sulfuric acid using the exothermic reaction to form a dry granulate, which is subsequently heated to 200-300C. By leaching the digestion products with water, the rare earth sulfates are dissolved, followed by separation of the rare earths from other soluble impurities by precipitation of sodium rare earth double sulfates, potassium rare earth double sulfates or rare earth oxalates.

Description

Field of application of the invention

The invention relates to the digestion of bastnäsite concentrates with medium contents of rare earths and larger contents of accompanying minerals such as baryte, fluorite, calcite and iron and manganese ores, by simple enrichment processes, in particular by refining of bastnasite ore from heavily weathered near-surface layers of the ore body a deposit of 10-12% SE ₂ O ₃ (rare earth oxides).

Characteristic of the known state of the art

Bastnäsit ores are mined in various countries (USA, Australia, PR China, Burundi, Madagascar) with contents of 2-10, preferably 7-10% SE2O3 and worked up by predominantly flotation on commercial concentrates with> 60% SE ₂ O ₃ .

Bastnäsite ores from the Mountain Pass / USA deposit with 7-10% SE ₂ O ₃ are finely minced by wet grinding and hot floated. In several flotation stages concentrates with 63% of SE ₂ O ₃ are obtained with 75-80% yield. The flotation aids used are sodium silicofluoride, ammonium lignosulfonate and oleic acid. The concentrate can be re-enriched to 68-74% SE ₂ O ₃ by treatment with hydrochloric acid and leaching of alkaline earth carbonates. (DRManeval, Mineral Industries 31 [1962], 8, 1-8)

From the Baiyun-ebo / PR China deposit bastnaesite concentrate with> 68% SE ₂ O ₃ is recovered by flotation with alkyl and arylhydroxyamic acids and oleic acid (Xu Xuefang, Wu Xianglin, Huang Linxuan, New Frontiers in Rare Earth Science Applications , Beijing 1985, 71-78).

The digestion of bastnäsite concentrates with high contents of rare earths can be done by various methods. Bastnäsit concentrate with> 60% SE ₂ O ₃ is added to 1.3 times the amount of concentrated sulfuric acid; The mixture is heated to 480 ° C and held at this temperature until the evolution of hydrogen fluoride is completed. The dry granulated sulphates are calcined at 650-750 ⁰ C, with most of the ingredients, except the Seltenerdsulfate be water-insoluble. The rare earth sulfates are leached from the digestion mass with cold water; By introducing the rare earth sulfate solution into boiling 50% sodium hydroxide solution, quite pure rare earth hydroxides are obtained (VE Shaw et al., according to LR Eyring, Progress in the Science and Technology of the Rare Earths, Vol 1, Oxford-London-New York-Paris 1964, pp. 42-43).

According to other data bastnaesite is digested at 200 ⁰ C with 100% excess of 98% sulfuric acid and complete to complete the removal of the Aufschlussesund Fluorsauf 900 ⁰ C heated. The resulting anhydrous rare earth sulfates are dissolved in cold water (R. Callow, Industrial Chemistry of the Lanthanons, Yttrium, Thorium, and Uranium, Oxford, London, 1967, pp. 78-79). According to another method, bastnaesite concentrate is treated with concentrated hydrochloric acid with 68-72% of SE ₂ O ₃ , whereby a part of the rare earths is obtained as a rare earth chloride solution. The insoluble residue consists of rare earth fluorides. By treatment with alkali hydroxide, the rare earth fluorides are converted to rare earth hydroxides. The washed rare earth hydroxides are used to neutralize excess hydrochloric acid in the previously obtained rare earth chloride solution (PR Kruesi and G. Düker, Journal of Metals 17 [1965], 847-849).

Also known is the calcination at about 65O ⁰ C of enriched by flotation to 60% SE ₂ O ₃ Bastnäsit concentrate, wherein the 3-cerium is converted into cerium (IV) oxide and fluorine is largely expelled. By treating the calcined product with hydrochloric acid, the trivalent rare earths are dissolved to leave a highly enriched cerium (IV) oxide (Anon., World Mining 19, 19666.3, 40-43).

Bastnäsite concentrates may also be treated by heating a suspension with concentrated caustic at 100-150 ° C to remove the fluorides contained. The rare earths are obtained as rare earth hydroxides. By heating to 500-700 ⁰ C residues of fluorocarbonates contained are destroyed and at the same time converted cerium (III) hydroxide to cerium (IV) oxide. By treating with hydrochloric acid, trivalent rare earth oxides are dissolved and cerium (IV) oxide remains unsolved (US Pat. No. 3,619,128).

Concentrates with> 60% SE2O3 are used in all of the processes mentioned. During enrichment to these levels, however, substantial amounts (over 25%) of the rare earths contained in the mined ores are lost during flotation.

It has therefore already been attempted to chemically work up bastnäsite ores with low contents of rare earths directly, bypassing 'flotation processes. Thus, a process has been reported in which bastnasite is calcined with 10% SE 2 O ₃ and proportions of CaCO ₃ , SiO ₂ and BaSO ₄ and treated with 57% nitric acid. After separating insoluble fractions, the rare earths are separated from alkaline earth nitrates by liquid-liquid extraction with tributyl phosphate and recovered by reextraction with water as a rare earth nitrate solution in 98% yield (CJ Baroch, M. Smutz, EH Olson, Mining Engineering 11, 1959, 3; 315-319). From bastnaesite ore containing 10.4% of SE ₂ O ₃ and proportions of CaCO ₃ , SrCO ₃ and BaSO ₄ , CaCO ₃ and SrCO _{3 were} selectively dissolved by the controlled addition of hydrochloric and nitric acid; the resulting residue from Seltenerdfluorcarbonat and BaSO ₄ was digested with concentrated sulfuric acid at 350 ⁰ C and the Seltenerdsulfate dissolved with water (DD Patent 233 810).

A disadvantage of the specified method for processing of Bastnäsit ore with low levels of SE ₂ O ₃ is that on the one hand the digestion with nitric acid with subsequent liquid-liquid extraction is expensive equipment and on the other hand, the work-up according to DD Patent 233,810 is limited to such Bastnäsit ores, which are free of fluorite, manganese and iron ores.

Object of the invention

The aim of the invention is to propose an economically favorable and easy to carry out process for the digestion of Bastnäsit concentrates with 25-38% SE ₂ O ₃ and high contents of accompanying minerals, such as baryte, fluorite, calcite, iron and manganese ores.

Explanation of the essence of the invention

The invention has for its object to make the digestion of Bastnäsit concentrates so that the use of raw materials and energy kept low, the accumulation of waste products by recycling largely avoided and the corrosion of the aggregates for the implementation of the method are largely eliminated.

It has been found that bastnaesite concentrates with 25-38% SE ₂ O ₃ and larger amounts of CaF ₂ , BaSO ₄ , MnO ₂ , Fe ₂ O ₃ , SiO ₂ , which are difficult to further enrich by flotation, by combining the following steps can be worked up advantageously:

Mixing the ground bastnasite concentrate with concentrated sulfuric acid to dry granules (I)

- heating the granules to the expulsion of F ~ as SiF ₄ / H ₂ F ₂ to 200-300 ⁰ C, preferably from 200 ⁰ C (II)

Dissolving the resulting rare earth sulfates together with iron sulfate by treatment with cold water (III)

Separation of undissolved portions of BaSO ₄ , CaSO ₄ , SiO ₂ , MnO ₃ by filtration (IV)

Separation of the rare earths from other impurities contained in solution by precipitation of the rare earths as sodium rare earth double sulfates by addition of sodium sulfate, separation of the double sulfates by filtration (V)

Reaction of the sodium rare earth double sulfates with sodium hydroxide solution to form rare earth hydroxides and sodium sulfate solution, separation of the rare earth hydroxides by filtration (VI)

- Combination of the filtrates of process steps V and Vl, precipitation of the contained fractions of Fe ³⁺ and Mn ²⁺ as Fe (OH) ₃ and MnO (OH) ₂ by addition of sodium hydroxide and oxidizing agents at pH 8-9 and traces of Zn ²⁺ , Ca ²⁺ and other divalent metals by subsequent addition of Na ₂ CO ₃ , separation of the precipitated products by filtration (VII)

- crystallization of Na ₂ SO ₄ · 10 H ₂ O from the obtained in process step VII of sodium sulfate by cooling to -5 ° C to +5 ⁰ C, and separation of the crystals by centrifugation or filtration (VIII)

Concentration of the sodium sulfate solution contained as filtrate in process step VIII and recycling for the precipitation of sodium rare earth double sulfates (IX)

The process according to the invention can be modified to the effect that, starting from process step V, potassium sulfate is used instead of sodium sulfate and potassium hydroxide is used instead of sodium hydroxide solution. In this case, the K ₂ SO ₄ solutions obtained in analogy VII can be supplied to the fertilizer production.

According to the invention, the bastnasite concentrate ground to <0.5 mm grain size is rapidly mixed with 100-150%, preferably 110%, of the amounts of technical concentrated sulfuric acid calculated to convert the oxides, carbonates and fluorides contained to sulfates, using an exothermic reaction and with development of SiF ₄ , H ₂ F ₂ and CO ₂ quite dry granules are formed. The mixing must be very fast, so that a largely homogeneous mixing of sulfuric acid with the Bastnäsit concentrate is achieved before onset of the exothermic reaction. To ensure mixing, the continuous metering of sulfuric acid and bastnaesite in a continuous, corrosion-resistant mixing unit (double paddle screw, co-kneader) equipped with a suction device is expedient. The resulting granules are heated to complete the digestion and the removal of F "for another 0.5-3 hours at 200-300 ⁰ C, this step is suitably carried out continuously in a directly heated with flue gas rotary drum will not be attacked when heated to 200 ° C of the main part of the existing MnO _2. Thus, the possibility is given to leave the MnO ₂ in the treatment of the decomposition product in the digestion residue. upon heating to 250-300 ⁰ C, however, a large part of the MnO ₂ to manganese (III) sulfate implemented. in treating the digested material with water then soluble manganese fall (II) sulfate, and MnO (OH) ₂ as a result of disproportionation at. the addition of reducing agents such as H ₂ O ₂ in treating the digested material with water, the MnO (OH) ₂ can be brought into solution as manganese (II) sulfate.

It was surprising that due to the contents of non-reacting with sulfuric acid components of Bastnäsit concentrate such as BaSO ₄ and SiO _2, the digestion can be carried out practically in the solid phase, with difficulties, usually in the digestion of similar concentrates with sulfuric acid in the liquid phase (High viscosity of digestion mash and thus the need to use strong stirrers, high corrosion effect of Aüfschlußmaische on the reaction vessels) can be avoided. The attack of the reaction product of Bastnäsit concentrate with sulfuric acid in the form of dry granules allows the continuation of the digestion by heating in rotary drums, both in terms of movement of the reaction product as well as in terms of energy input significant energy savings compared to the use of heated.Rührmaschinen occur.

Surprisingly, the relatively low temperature of the digestion by the process according to the invention was compared to known methods in which worked with digestion temperatures of 350-900 ° C, relatively low temperature.

Since relatively much Fe ³⁺ passes into the rare earth sulfate solution obtained after the leaching of the digestion ^product in the process according to the invention, the separation of rare earths and Fe ³⁺ by precipitation of the rare earths is required as sodium rare earth double sulfates.

Alternatively, the separation by precipitation of the rare earths as rare earth oxalates can take place, it being advantageous that impurities, in particular Ca ²⁺ , can be better separated from the rare earths. The basic variant of the process according to the invention is characterized by the complete recovery of sodium sulfate or the return of sodium sulfate solution in the work-up process. Thus, the accumulation of water-soluble waste products and the pollution of the waters by sodium sulfate is avoided.

Alternatively, the treatment with calculated amounts of calcium chloride and calcium hydroxide instead of the reaction of the filtrate obtained as sulfate solutions with sodium hydroxide solution. Thus, the polyvalent metal ions are precipitated as hydroxides and SOl ⁺ as calcium sulfate. The precipitated products can be fed to the solids landfill after separation from the filtrate. The then only NaCl containing filtrate can be fed without hesitation to the wastewater.

The invention will be explained in more detail with reference to embodiments.

example 1

10 oz Bastnäsit concentrate with 31.2 ⁰ ASE ₂ O ₃

and grain size 100% <0.5 mm were rapidly mixed with 66 g of 96% sulfuric acid, the mixture heated to 100 ° C with evolution of SiF ₄ / H ₂ F ₂ / CO ₂ gases in an exothermic reaction. The mixture was obtained in the form of a brown, dry granule with granules of 2-5 mm diameter. The granules were heated in a bowl with occasional stirring for 2 hours at 250 ⁰ C and then had a dark green coloration by manganese (III) sulfate formed. During mixing and heating, the liberated SiF ₄ / H ₂ F ₂ gases were sucked through a funnel and absorbed in water in a wash bottle. The reaction product was cooled to 25 ⁰ C and added with stirring in 550ml of ice water. The mixture was stirred for 3 hours, whereby the existing MnO ₂ and Ce (SO ₄ ) _{2 were} reduced by gradual addition of 6 g of 96% sulfuric acid and 6 ml of 30% hydrogen peroxide. The temperature during the treatment was kept at <15 ⁰ C. The gray-white solution residue sedimented rapidly; it was then filtered off, washed with 2 × 50 ml of water and dried at 300 ×. Received:

46.6 g residue with 8.6% CaO

0.4% SrO 35.8% BaO

3.6% SE ₂ O ₃

1.5% PbO

0.2% MnO ₂

1.2% F

7.8% SiO ₂ 34.6% SO ₃ and

- 620ml acid sulfate solution with 29.5g SE ₂ O ₃

6.7 g of Fe ₂ O ₃ 3.9 g of MnO 1.2 g of CaO 0.5 g of ZnO

From this sulfate solution was precipitated by addition of 150 ml of hot Na ₂ SO ₄ solution with 40 g of Na ₂ SO ₄ and heating to 90 ⁰ C, the SE ³⁺ almost completely as sodium rare earth double sulfates. The double sulfates were filtered, washed with 50 ml of hot Na ₂ SO ₄ solution (2.5 g Na ₂ SO ₄ Zoomi solution) and dried at 100 ⁰ C. It received:

74g sodium rare earth double sulfate with 39.5% SE ₂ O ₃

1.6% CaO

By reacting the double sulfates to form rare earth hydroxides by boiling with 240 g of 10% sodium hydroxide solution, filtering, washing and drying at 100 ⁰ C were obtained:

37.5 g of rare earth hydroxides with 78.2SE ₂ O ₃

3,1CaO

Thus, 93.9% of the rare earth contained in the starting material was recovered as rare earth hydroxides. The filtrates from the precipitation of sodium rare earth double sulfates and the reboiling of the double sulfates to rare earth hydroxides were combined, adjusted to pH 8 with 50 g of 50% sodium hydroxide solution and heated to 85 ° C. after addition of 3 g of anhydrous sodium carbonate. In this case, the contents of Fe ^{3+ were} precipitated as Fe (OH) ₃ . By introducing air, the existing Mn ^{2+ was} oxidized and precipitated as MnO (OH) ₂ . The precipitate contained the amounts of Fe ³⁺ , Mn ² VMn ⁴⁺ and Zn ²⁺ contained in the combined combined filtrates. It was filtered off, washed with hot water and fed to the landfill. 1000 ml of clear sodium sulfate solution containing 120 g of Na ₂ SO ₄ were obtained as filtrate. From the solution, anhydrous sodium sulfate was recovered by a known method. The resulting mother liquor was used again for the precipitation of sodium rare earth double sulfates.

Example 2

As in Example 1, 100 g bastnasite concentrate were digested with sulfuric acid. The reaction product was leached with water. From the filtered solution, sodium rare earth double sulfates were precipitated by sodium sulfate. After separation of the double sulphates, the filtrate at 70 ⁰ C with 80 g of 20% igerCaCI ₂ solution and milk of lime according to 25g Ca (OH) ₂ was added and adjusted to pH 8.5. In this case, the contents of Fe ^{3+ were} precipitated as Fe (OH) ₃ . By introducing air into the alkaline solution, Mn ^{2+ was} oxidized and precipitated as MnO (OH) ₂ . The resulting suspension of CaSO ₄ .2H ₂ O, Fe (OH) ₃ and MnO (OH) ₂ in NaCl solution is fed to the landfill.

Example 3

100 g Bastnäsit concentrate of the composition and grain size listed in Example 1 were moistened with 10 ml of water and rapidly mixed with 60 g of 96% sulfuric acid, the mixture with evolution of SiF ₄ / H ₂ F ₂ / CO ₂ gases to 95 ⁰ C heated and a brown, dry granules formed. The granules were heated in a pan for 4 hours at 200 ⁰ C with occasional stirring. The brown remaining granules were cooled to 25 ° C and added in 600 ml of water at 8 ° C. The slurry was stirred for 4 hours, keeping the temperature <15 ° C. The brown solution residue sedimented rapidly. It was filtered off, washed with 2 × 50 ml of water and dried at 300 ° C. Received:

- 54g residue with 7.5% CaO

0.4% SrO 30.9% BaO

6.5% SE ₂ O ₃

1.3% PbO

8.5% MnO ₂

1.2% F

6.7% SiO ₂ 32.6% SO ₃ and

- 600 ml of acidic sulphate solution

The sulfate solution with pH = 0.8 was 40gtechn. With stirring. Oxalic acid (C ₂ H ₂ O ₄ 2H ₂ O) and heated to 7O ⁰ C. After cooling, the precipitated rare earth oxalates were filtered off, washed with water and dried at 105 ⁰ C. Received:

56.5g of rare earth oxalate with 49.0% SE ₂ O ₃

0.2% CaO Thus, 88.8% of rare earth contained in the raw material was recovered as a rare earth oxalate.

Claims (5)

- 1 - . CO i. Ο * ΚΪ claims: 1. A method for the digestion of Bastnäsit concentrates with average contents of rare earths and high levels of baryte, fluorite, calcite and iron and manganese ores with sulfuric acid, characterized by the method steps - Reaction of Bastnäsit concentrate with concentrated sulfuric acid to a dry granules - Heating the granules to 200 to 300 ⁰ C over 0.5 to 3 hours - Dissolve the rare earth sulfates formed in the granules by treatment with water - Precipitation of the rare earths from the solutions as sodium rare earth double sulfates, potassium rare earth double sulfates or rare earth oxalates. 2. The method according to claim 1, characterized in that for the digestion of Bastnäsit concentrate 100 to 150% of the calculated for the implementation of the oxides, carbonates and fluorides contained in sulfates amount of concentrated sulfuric acid is applied. 3. The method according to claim 1 and 2, characterized in that the implementation of Bastnäsit- , Concentrate with sulfuric acid is carried out continuously in a double paddle screw or a kneader. 4. The method according to claim 1 to 3, characterized in that the heating of the granules is carried out continuously in a directly heated rotary drum. 5. The method according to claim 1 to 4, characterized in that sodium sulfate is recovered from filtrates of the double sulfate precipitation by precipitation of polyvalent cations with sodium hydroxide solution and sodium carbonate.