US3082872A - Froth flotation of cryolite - Google Patents

Description

United States Patent 3,082,872 FROTH FLOTATION F CRYOLITE Artur Ernst Heinrich Bergmann, Meggen A.D. Lenne, Germany, assignor to Klockner-Humholdt-Deutz Aktiengesellschaft, Koln-Deutz, Germany, a corporation of Germany No Drawing. Filed May 3, 1961, Ser. No. 107,327 Claims priority, appiication Germany May 6, 1960 4 Claims. (Cl. 209-167) My invention relates to a froth flotation method for cryolite.

Cryolite deposits generally contain about 80 to 85% cryolite, the remainder being fluorspar, iron spar (siderite), quartz, sulfides, thomsenolite, pachnolite and hagemannite.

It is an object of my invention to eliminate the just mentioned impurities by a froth flotation method.

Since the ore is often intimately mixed with gangue, the ore must be ground down to minus 100 microns (0.1 millimeter).

According to a known method, the ore is first subjected to sulfide flotation, whereafter the cryolite itself is activated by addition of sodium fluoride, so that it can be carried off by means of fatty acids or their soaps, after several subsequent purifying stages. This method has the following disadvantages:

(1) Several subsequent purifying stages are necessary (2) A long froth-forming time and therefore a large cell volume is necessary, because the major portion of the ore, cryolite, is floated away;

(3) Cryolite, enriched in the froth, causes considerable difliculties in the further fabricating processes because such cryolite is no longer wettable.

According to my invention, a considerable improvement of the flotation process is achieved by proceeding as follows. The pulp, in acidic condition, is provided with copper sulfate or a similar medium and is processed by means of a collecting agent and a frothing agent, in order to float away the major portion of the impurities. The first stage discharge is then floated in a second stage by use of a fatty-alcohol-phosphorus acid ester salt, likewise in an acidic bath, in order to float away the residue of the impurities. The flotation is eliected in an acidic pulp in order to prevent floating of the cryolite.

In the first stage, the sulfides of the gangue are sufficiently activated by the addition of copper sulfate and an acid. Conversely, the cryolite is sufliciently passivated by addition of the copper sulfate. When quartz is present in the gangue, the method of the invention can be further improved by adding a cation-active medium, for example an amine, to the second stage. This has the advantage of increasing the elimination of quartz.

The following example relates to an ore containing on the average 80% cryolite, 3% fluorspar, 8% siderite, the residue consisting of quartz, sulfides, pachnolite, thomsenolite and hagemannite. The ore was ground to a grain size of minus 100p and was processed in the first flotation stage at 250 g. solids per liter. Sulfuric acid was used to adjust the pH of the pulp to about 5.0. City water of Cologne, Germany, having a hardness of 17 DH was the water used. The reagents used were as follows:

Stage 1 1O kg./t. CuSO 300 g./t. H 50 200 g./t. potassium ethyl xanthate (collecting agent) 40 g./ t. pine oil (frothing agent) The first stage concentrate was supplied to a second flotation stage in which the following reagents were consumed:

Stage 2 250 g./ t. sodium laurylphosphate 55 g./t. laurylpyridiniumbromide (cationic collecting agent) It is preferable that the sodium lauryl phosphate is added to the second stage in two portions, of which the second portion is added toward the end of the second flotation stage. It is also preferable to add the cationic collecting agent at this time. As a rule, it is not necessary to add acid in the second stage, because the addition of acid to the first stage is suflicient in most cases for the second stage also to be acidic. In the example described above, the pH value in the second stage increased to about 6.8.

The flotation had the following result:

Cryolite Weight Percent Percent Percent Output Froth products 30. 6 36. 00 14. 0 Concentrate 69. 4 97. 08 86. 0

In another example, the following reagents were consumed:

Stage 1 10 kg./t. CuSO 200 t. H2804 200 g./t. potassium ethyl xanthate (collecting agent) 40 g./t. pine oil (frothing agent) Stage 2 250 g./t. sodium laurylphosphate 55 g./t. laurylpyridiniumbromide The pH values were similar to those listed in the first example.

The flotation had the following result:

1. A froth flotation method for recovering cryolite, comprising acidifying a cryolite ore pulp, said cryolite ore pulp containing impurities comprising sulfides, fluorspar and siderite, adding in a first stage copper sulfate, potassium ethyl xanthate and pine oil to float the sulfide impurities, adding in a second stage sodium laurylphosphate to float the remainder of the impurities.

2. A froth flotation method for recovering cryolite, comprising acidifying a cryolite ore pulp, said cryolite ore pulp containing impurities comprising sulfides, fluorspar, siderite and quartz, adding in a first stage copper sulfate, potassium ethyl xanthate and pine oil to float the sulfide impurities, adding in a second stage sodium laurylphosphate and laurylpyridiniumbromide to float the remainder of the impurities.

3. A froth flotation method for recovering cryolite, comprising acidifying a cryolite pulp containing impurities comprising sulfides, fluorspar and siderite to a pH of 5, adding in a first stage copper sulfate, potassium ethyl xanthate and pine oil to float the sulfide impurities, adding in a second stage sodium laurylphosphate to float the remainder of the impurities.

4. A froth flotation method for recovering cryolite, comprising acidifying a cryolite pulp containing impurities comprising sulfides, fluorspar, siderite and quartz to 5 a pH of '5, adding in a first stage copper sulfate, potassium ethyl xanthate and pine oil to float the sulfide impurities, adding in a second stage sodium laurylphosphate and laurylpyridiniumbromide to float the remainder of the impurities, whereby the major portion of the cryolite 10 remains in the concentrate,

References Cited in the file of this patent UNITED STATES PATENTS Schranz July 17, 1934 Lenher Oct. 11, 1938 Zenftman Aug. 21, 1956 Goldenhar Dec. 20, 1960 Hazen June 5, 1962 FOREIGN PATENTS Germany Aug. 27, 1937

Claims (1)

1. A FROTH FLOTATION METHOD FOR RECOVERING CRYOLITE, COMPRISING ACIDIFYING A CRYOLITE ORE PULP, SAID CRYOLITE ORE PULP CONTAINING IMPURITIES COMPRISING SULFIDES, FLUORSPAR AND SIDERITE, ADDING IN A FIRST STAGE COPPER SULFATE, POTASSIUM ETHYL XANTHATE AND PINE OIL TO FLOAT THE SULFIDE IMPURITIES, ADDING IN A SECOND STAGE SODIUM LAURYLPHOSPHATE TO FLOAT THE REMAINDER OF THE IMPURITIES.