RU2247695C1 - Method for production of spectral-pure lithium carbonate - Google Patents

Abstract

FIELD: analytical chemistry, in particular method for production of spectral-pure lithium carbonate.

SUBSTANCE: spectral-pure lithium carbonate is obtained by reaction of lithium hydroxide with hydrochloric acid followed by reaction with ammonium carbonate. Obtained lithium chloride solution hawing pH 8-9 is filtered and fed into chelating resin. Then lithium carbonate is precipitated with saturated ammonium carbonate solution, filtered, washed with hot distillated water, ethanol, and dried. Method of present invention makes it possible to obtain lithium carbonate containing <0.001 mass % (in respect to lithium) of sodium, potassium, and calcium.

EFFECT: method of improved efficiency.

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Description

The present invention relates to the field of analytical chemistry, and in particular to a method for producing spectrally pure lithium carbonate.

Recently, high demands have been placed on the purity of commercial lithium products for calcium, so the content of sodium, potassium and calcium in lithium metal battery grade should not exceed respectively 0.008 mass%, 0.003 mass% and 0.02 mass%. Requirements for the calcium content in lithium metal is 0.01 mass% fractions. To analyze products of this purity, lithium carbonate with a calcium content of 0.001 mass% by weight relative to lithium is required.

A known method of purification of industrial lithium carbonate, containing impurities of calcium, magnesium, potassium and sodium, by passing carbon dioxide through a suspension of lithium carbonate. In this case, readily soluble lithium bicarbonate is obtained, the concentration of which in the solution is 50-60 g / l of salt in terms of lithium carbonate. After separation of insoluble impurities, the unstable bicarbonate salt was destroyed by boiling, while lithium was isolated from the solution in the form of carbonate (Yu.I. Ostroushko et al. Lithium, its chemistry and technology. - M.: Atomizdat, 1960, p. 122).

The disadvantages of this cleaning method include the use of pressure equipment (autoclaves), insufficiently deep cleaning of calcium (calcium content at the level of 4 · 10 ^-2 wt.%% Relative to lithium).

Closest to the proposed method for producing spectrally pure lithium carbonate is the prototype method described in GOST 8775.3-87 (Lithium. Method for the determination of magnesium, manganese, iron, aluminum, silicon, barium. Appendix). Initially, a solution of lithium chloride is obtained by neutralizing lithium hydroxide with distilled hydrochloric acid (GOST 3118-77), and subsequently, operations are carried out by the deposition of carbonic ammonium, oxalic ammonium and filtration. In addition, the ethylene diamine-N, N, N’, N’-tetraacetic acid diammonium salt and saturated ammonium carbonate solution are added to the lithium chloride solution until the precipitation of lithium carbonate ceases, the solution is stirred and allowed to settle. The precipitate is washed three times with hot distilled water, ethyl alcohol, acetone, dried on a tray and in an oven.

The disadvantages of this method of obtaining spectrally pure lithium carbonate include the duration of the process and the fact that the purification of the obtained lithium carbonate with calcium (<0.001 wt.% With respect to lithium) is not achieved.

The objective of the invention is to obtain spectrally pure lithium carbonate in a more economical way with a content of sodium, potassium and calcium <0.001 mass. % fraction in relation to lithium.

The solution to this problem is achieved by the fact that in the method for producing spectrally pure lithium carbonate by reacting lithium hydroxide with hydrochloric acid according to the claims, the resulting lithium chloride solution with a pH of 8-9 is filtered and sent to a column with a chelating resin, after which lithium carbonate is precipitated with ammonium carbonate , lithium carbonate is filtered off and washed with hot distilled water, ethyl alcohol and dried.

The specified set of features is new and has an inventive step, because neutralization of lithium hydroxide with hydrochloric acid to pH 8-9 allows you to leave aluminum and heavy metal impurities in undissolved form and filter them, as well as the pH of the chelating resin cleans the solution more efficiently from calcium, the cleaning depth in calcium (<0.001 mass.% by with respect to lithium) is achieved only with the use of chelating resins, the precipitation of lithium carbonate with ammonium carbonate allows to achieve additional purification from sodium and potassium (<0.001 mass% with respect to lithium), washing the carbonate precipitate lithium is necessary to remove chlorine ion and impurities contained in the mother liquor. The washing of lithium carbonate with rectified ethyl alcohol is carried out in order to reduce lithium losses. Drying lithium carbonate to a constant weight is necessary in order to take accurate weights in the preparation of standard solutions.

The method for producing spectrally pure lithium carbonate is carried out as follows: a weighed portion of lithium hydroxide (grade LGO-1) is moistened with distilled water and neutralized with distilled hydrochloric acid of the osch grade (GOST 3118-77) to pH 8-9, then the solution is filtered on a Buchner funnel through the “blue ribbon” filter. A solution of lithium chloride is sent to a chelating resin prepared for calcium sorption (MIC, Pyurolight S940). After cleaning the lithium chloride solution on the resin from calcium, lithium carbonate is precipitated with a saturated solution of ammonium carbonate. The precipitate of lithium carbonate is filtered off and washed with hot condensate and ethyl alcohol from chlorine ion and impurities contained in the mother liquor.

An example of obtaining spectrally pure lithium carbonate:

~ 1 kg of lithium hydroxide brand LGO-1 (GOST 8595-83) is dissolved in distilled water and neutralized with hydrochloric acid (36%) brand “osch”. The resulting lithium chloride solution had a concentration of ~ 100 g / l and a pH of 8-9. The lithium chloride solution is filtered on a Buchner funnel through a blue ribbon filter and passed through a column (L = 3.5 cm; H = 100 cm) filled with Purolight S940 resin in Li-form at a rate of 200 ml / hour. After passing through the column, the solution is analyzed for sodium, potassium, and calcium. The following analysis results are obtained: Na - 1.9 · 10 ^-3 % to Li, K - 3.2 · 10 ^-3 % to Li, Ca - 8.4 · 10 ^-4 % to Li. In a container with a capacity of 20 l, ~ 7 l of saturated ammonium carbonate solution (obtained by saturating the osch ammonium hydroxide from a cylinder) and a lithium chloride solution are mixed and a lithium carbonate precipitate is mixed. After a day, the precipitate of lithium carbonate is separated by decantation from the solution and washed three times with hot distilled water.

The precipitate of lithium carbonate is mixed with rectified ethyl alcohol (2 volumes of alcohol per 1 sediment volume), and after ~ 1 hour after settling, the alcohol is drained. The precipitate is unloaded on tracing paper and dried at room temperature for one day, and then in an oven for one hour at a temperature of 100-110 ° C. The resulting lithium carbonate is analyzed for sodium, potassium and calcium. The following analysis results were obtained: Na - 4.0 · 10 ^-4 % to Li, K - 5.9 · 10 ^-4 % to Li%, Ca - 8.9 · 10 ^-4 % to Li%.

Claims (1)

A method for producing spectrally pure lithium carbonate by reacting lithium hydroxide with hydrochloric acid, characterized in that the resulting lithium chloride solution with a pH of 8-9 is filtered and sent to a column with a chelating resin, then lithium carbonate is precipitated with ammonium carbonate, lithium carbonate is filtered off and washed hot distilled water, ethyl alcohol and dried.