US3827556A - Purification of kaolin clay by froth flotation - Google Patents

Abstract

A method for removing finely divided particles of a colored titaniferous impurity from a dispersed alkaline pulp of kaolin clay by froth flotation. The collector for the impurities is a very low rosin acid tall oil which also provides controlled frothing without the addition of hydrocarbon oils to prevent overfrothing.

Description

United States Patent [191 Mallary ['11] 3,827,556 [45] Aug. 6, 1974 PURIFICATION OF KAOLIN CLAY BY FROTH FLOTATION [75] Inventor: Miller B. Mallary, Macon, Ga.

[73] Assignee: Engelhard Minerals & Chemicals Corporation, Woodbridge, NJ.

. 7/1958 Duke 3,635,337 l/l972 Mercade 209/166 X 3,640,382 2/l972 Jepsen 209/166 FOREIGN PATENTS OR APPLICATIONS 598,311 5/1960 Canada 260/975 Primary Examiner -Robert Halper Attorney, Agent, or Firm-Melvin C. Flint; Inez L. Moselle [57] ABSTRACT A method for removing finely divided particles of a colored titaniferous impurity from a dispersed alkaline pulp of kaolin clay by froth flotation. The collector for the impurities is a very low rosin acid tall oil which also provides controlled frothing without the addition of hydrocarbon oils to prevent overfrothing.

5 Claims, No Drawings PURIFICATION OF KAOLIN CLAY BY FROTH FLOTATION BACKGROUND OF THE INVENTION in various froth flotation processes. These oils are among the cheapest organic materials available and they are considerably less expensive than oleic acid and other pure higher fatty acids. In many cases, the impure tall oils are more selective than pure fatty acids as collectors. It is well known, however, that the high rosin tall oils tend to cause overfrothing of alkaline flotation pulps, especially so in the case of slimey pulps. Overfrothing results in dilution of mineral values by floating slimes when the values are recovered in the froth. Low recoveries of mineral values are experienced when the mineral values report in the flotation tailings,

To avoid the excessive, voluminous froth obtained when tall oil'is used as a collector in a strongly alkaline pulp, it is common practice to modify the flotation pulp by adding a neutral hydrocarbon oil tov control the froth. In some cases, petroleum sulfonates may be used as a substitute for a portion of the tall oil. However, even when the combination of collectors is employed, it is usually essential to use a neutral oil to control the froth.

The factors discussed above have been instrumental in the selection of a four oil system for floating colored titania impurities from Georgia kaolinclay in commercial froth flotation. In the process, colored impurities, principally yellowish titaniferous impurities, are floated from an alkaline dispersed pulp of impure kaolin clay with an anionic collector and a calcite carrier. The collector reagent is a mixture of a relatively high rosin content tall oil (28 percent rosin acids) with an oilsoluble petroleum sulfonate. The two oils are added to a deflocculated alkaline clay pulp during conditioning. In order to curb the froth which would be produced during conditioning, a neutral oil, preferably a lube oil, is added during conditioning. Flotation is carried out on a continuous basis. The rougher froth which is a concentrate of the carrier particles and the colored impurities is successively refloated in stages and the froth products from reflotation and scavengering may be impounded. The machine discharge products (tailings) are combined and contain the dispersed purified clay which is recovered. During rougher and cleaner flotations a neutral hydrocarbon oil, preferably fuel oil, is added to the pulp in order to minimize losses of clay in the froths. Typically 5-7 lbs/ton of a neutral lubricating type oil is added during conditioning and a total of 3 lbs/ton of fuel type oil is added during flotation.

By such practices there is efficient removal of colored impurities at clay recoveries above 85 percent. However, in some instances trace residues of the flotation oils contaminate the slip of flotation purified clay and the clay will fail to respond to the expected extent to bleaching by a hydrosulfite salt (which is a conventional bleach reagent for clay).

Various methods have been suggested to remove the residual oils from flotation beneficiated clay. However, these solutions merely compensate for a problem and do not attack the source of the difficulty. It is apparent that there is a need for developing a clay flotation process which utilizes a reasonably inexpensive collector 2 which is adequately selective to the colored impurities in the clay and which obviates the need to use neutral 7 oils for froth control purposes.

THE INVENTION An object of the invention is to provide an improvement in a process for removing colored impurities from kaolin clay whereby a single oil may be used as the collector-frother.

Another object is to provide a method for floating titaniferous impurities from kaolin clay which provides high yields of uncontaminated purified clay at a commercially feasible reagent cost.

The essence of my invention resides in subjecting a pulp of impure kaolin to froth flotation in the presence of tall oil containing 1 percent to 5 percent rosin acids and the balance essentially a mixture of unsaturated higher fatty acids as the sole oily reagent, the tall oil functioning both as the collector for the titania and to provide controlled frothing. The use of this limited class of tall oils obviates the need for amultiple oil system while providing adequate collection of titania and controlled frothing. The beneficiated clay has better brightness both before and after bleaching as a result of reduced reagent contamination. These results may be achieved without increasing the cost of flotation reagents.

PRIOR ART The following US. patents disclose the use of various fatty acids or-tall oil acids as collectors for titania impurities in the froth flotation of kaolin clay.

No. 2,569,680 Leek No. 2,990,958 Greene et a].

No. 3,224,582 lannicelli No. 3,450,257 Cundy No. 3,599,879 Clark No. 3,151,062 to Duke is concerned with the problem of froth control in the flotation beneficiation of kaolin clay and is especially concerned with the use of hydrocarbon oils to control frothing.

'The references above cited, as well as others cumulative thereto with regard to their disclosures of flotation collectors for a titaniferous impurity in kaolin clay, fail to disclose or to suggest the inventive concept to which this patent application is directed.

DETAILED DESCRIPTION As used herein, the term tall oil is used in accordance with widely accepted definition (A.S.T.M. D804-54) i.e., the natural mixture of rosin acids related to abietic acid and of fatty acids related to oleic acid, together with nonacidic bodies, which is obtained by acidifying the black liquor skimmings of the alkaline paper pulp industry.. Crude tall oils usually contain from 28 percent to percent rosin acids and from about 5 percent to 24 percent nonacid bodies, depending upon the wood species which it is derived from.

The tall oils used in carrying out the present invention are obtained by refining crude tall oil by distillation with recovery of a fatty acid-enriched fraction or by distillation plus other conventional refining such as acid treatment or adsorption to remove color bodies and oils. These refined tall oils are usually appreciably lower in nonacid bodies than crude tall oils and consist essentially of rosin acids and fatty acids, the fatty acids being present in proportions typical of the parent crude oils. Thus, the single flotation oil I employ to beneficiated clay is a refined tall oil containing 1 percent to percent, preferably 2 percent to 4 percent rosin acids, the balance being essentially a mixture of oleic acid and linoleic acid in weight proportions of about 50/50. Nonacid bodies (unsaponifiables) are-usually below 2 percent. The combined fatty acid and rosin acid content of the refined tall oils I employ is usually 98 percent or above.

Tall oils containing less than 1 percent rosin acids lack the selectivity of tall oils having a higher rosin content and the use of such highly refined oils is therefore outside the scope of my invention. Similarly, pure fatty acids such as oleic or linoleic acid, or mixtures thereof, have been found to be less selective than tall oils having a small but significant rosin acid .content. Consequently, it is essential to use an oily collector containing a small but limited amount of rosin acids. Further, the pure fatty acids and the essentially rosin-free tall oil acids are considerably more expensive than the low rosin tall oil products I employ. On the other hand,

when the rosin content of a tall oil exceeds 5 percent, the clay recovery is reduced in the absence of oily froth modifiers which I exclude to avoid excessive contamination of the clay product. Tall oil products containing rosin acids in the preferred range of 2 percent'to 5 percent by weight provide the best balance between clay recovery, selectivity and cost.

In putting my invention into practice, the low rosin tall oil may be used in acid form or the acids may be saponified before addition to the pulp. Alternatively the tall oil may be emulsified in a dilute solution of ammonium hydroxide.

The preferred deflocculating agent for the clay pulp is sodium silicate which is preferably added as a dilute hydrosol, as described in Mercade Pat. No. 3,337,048.

The presently preferred flotation process uses a flotation carrier, preferably calcite, as described in U.S. Pat. No. 2,990,948. Such process is hereinafter referred to as Ultraflotation. It is within the scope of the invention, however,'to omit the carrier, especially when beneficiating coarse kaolins or.when employing high energy conditioning (e.g., energy inputs of 50 hp. hr./ton or above).

The amount of low rosin tall oil used is generally within the range of 5 to lbs./ton of dry clay when practicing Ultraflotation. When a carrier reagent is not employed, the quantity of the tall oil may be reduced, e.g., to 1 to 2 lbs/ton.

Conventional frothers, e.g., pine oil, are not required when using a low rosin tall oil as the collector-frother in my process. I have found that the use of pine oil in conjunction with a low rosin tall oil reduced the yield of beneficiated clay.

The patents cited hereinabove provide detailed descriptions for preparing kaolin clay crudes for flotation. Briefly, the steps involve blunging, degritting, particle size fractionation and deflocculation of the pulp. Procedures conventional in the flotation art may be used for conditioning and flotation. Reference is made to U.S. Pat. No. 2,990,958 for details of the Ultraflotation process. As shown in this patent, the froth from the rougher flotation is reconditioned without addition of collector and refloated to remove residual clay. The froth of this flotation may be cleaned one or more times by reflotation. The final froth may be discarded. The

combined tailings, which contain the purified clay, are usually flocculated by addition of acid or alum and then the clay is bleached, filtered and washed. The bleach reagent used will depend upon the type of clay employed. Conventional soft white clays may require only a reduction bleach (e.g., a hydrosulfite salt). Gray kaolins may require treatment with a strong oxidant such as ozone or potassium permanganate prior to the reduction bleach unless the gray clay has been ozonated or otherwise oxidized prior to flotation.

The invention and its advantages will be better understood from the illustrative example which follows.

In the example, all brightness values were obtained by the conventional TAPPI procedure (T-646 m-54). Quantities of reagents were reported as pounds per ton of dry clay in the clay pulp.

The clay used as the starting material in all tests was a soft sedimentary Georgia kaolin crude representative of the clays used to provide No. 1 coating clays. The crude was blunged in water at 40 percent solids. The resulting pulp was partially dispersed by adding a 5 percent solution of soda ash (2.2 lbs/ton), bringing pH to 7.5. To the pulp there was added as a deflocculant a hydrosol obtained by mixing a 5 percent solution of N sodium silicate solution with a 1 percent solution alum in amount corresponding to 6 lbs/ton N and 0.6 lb./ton alum. The pH was about 8.5. The pulp was allowed to stand for 10 minutes to permit grit to settle out and the supernatant was decanted. The decanted slip was fractionated in a centrifuge and a slip of fine clay percent finer than 2 microns) was recovered. All slips of clay used in the example had been prepared in this manner.

EXAMPLE This example demonstrates the necessity for selecting a low rosin acid oil in a single oil process for floating colored titania from clay in order to obtain a high recovery of high brightness beneficiated kaolin clay.

In tests carried out to study the effect of the rosin content of tall oil on flotation parameters, oils containing 0 percent, 0.6 percent, 3.0 percent, 7.0 percent, 26 percent and 45 percent were used. Since a rosin-free tall oil was not available, it was synthesized by making a 50/50 (wt.) blend of oleic acid and linoleic acid. The other oils were commercial products which are characterized in Table I.

Portions of the slip of degritted fractionated clay at 20 percent solids were conditioned for 22 minutes in a Fagergren conditioner with 400 lbs/ton Drikalite (minus 325 mesh calcite), ammonium sulfate (5 percent solution) added to pH 8.2, and 9 lbs/ton of one of the tall oil products described above. After conditioning the pH was adjusted to 8.6 with ammonium hydroxide. No other oils or frothers were used. Flotation was carried out in a batch laboratory cell for minutes. The underflow (machine discharge product or MD-1) of the flotation cell containing the partially purified clay was Weighed to scertain yield f h 5 percent to 26 percent. However, the high rosin acid rougher flotation. The froth from the rougher flotation system was impractical because of the low clay yield. was diluted and cleaned by reflotation for 10 minutes. The froth was discarded and the underfl0 Data in Table 11 therefore show that the Ultraflotawas recovered and weighed o determine recovery- The tion could be carried out in the absence of a petroleum MDl and MD-2 products Were com ined to pr 10 sulfonate or fuel oil modifiers without sacrificing clay the beneficiated clay slip. yield by using a commerical tall oil containing 3 per- A portion of each beneficiated slip Wa leach n cent rosin acids. When the oil contained less than 1 standard co ent a manne as o s- Th slips percent rosin acids, titania removal was less than could were acidified by addi g sulfuric acid o pH and n be obtained with 3 percent rosin acid and when the oil Zine hydrosulfite was ed in a o n of lbs/i011- 15 contained 7 percent rosin acid or more clay recoveryv During bleaching, pH was maintained at 3.0 by addiwas i d t tion of sulfuric acid. Bleaching time was one-half hour. 1 i

Three runs were made for .each collector investi- 1. In a method for removing discrete colored titanifgated. erous impurities from a fine size fraction of degritted Analyses of the flotation yields and kaolin clay wherein a dispersed alkaline pulp of the iml ached and unbleached brightness, n t ni pure clay is subjected to froth flotation in the presence analysts are g p age values) in able II. r n anionic collector for the titaniferous impurities TABLE ll percent when rosin acid was 26 percent. Unbleached brightness results reflected this trend. Bleached brightness (standard) increased from 90.4 percent to 90.9 percent when rosin acid content was increased from 0 EFFECT OF ROSlN ACID CONTENT OF TALL OlLS ON FLOTATlON BENEFlClATlON OF KAOLlN CLAY SINGLE OlL-FROTH FLOTATION Weight Percent Brightness percent Flotation Yield Weight percent TiO Unbleached Bleached Rosin In I Collector MD-l MD-2 Total a d OR" 0 76.3 11 3 87.6 0.53 87.5 90 4 90.6 0.6 71.5 18 5 90.0 0.49 85.0 90.2 90.6 3.0 60.0 27.3 87.3 0.43 85.6 90.4 91.1 7.0 44.5 29.3 73.8 0.42 86.1 90.2 91.0 26.2 34.4 32.4 66.8 0.31 89.1 90 7 9l.l 43.0 32.3 37 7 70.0. 0.33 89.0 91 2 91.7 Control (no 1.64 81.0

flotation) 'zns o, ""KMnO +ZnS,O

Data in Table II for flotation yields obtained with tall oils of varying rosin acid contents as the single flotation oil show that thev yield of clay in the rougher flotation (MD-l) varied from 76 percent, when no rosin was present, to only 32 percent, when the rosin acid content was 43 percent. Overall recovery varied from 90.0 percent, when 0.6 percent rosin was present, to 70.0

percent with 43 percent rosin. The yield during rougher flotation was 60 percent when the tall oil contained 3 percent rosin acids, whereas the rougher yield was percent lower than this value when the tall oil contained 7 percent rosin acids. Total yield was almost 15 percent greater when the tall oil contained 3 percent rosin acids than it was when using tall oil with 7 percent rosin acids.

The results for yields on rougher and cleaner flotation clearly indicate that when the rosin acid content of a tall oil is substantially in excess of 3 percent, more flotation cells will be required to clean the clay and the recovery of beneficiated clay will be less than when using tall oils containing less rosin acids.

Titania analyses in the table show that titania removal was directly related to the rosin content of the oily collector. When the collector was free from rosin, 68 percent TiO was removed This was increased to 81 and means is provided for imparting controlled frothing characteristics to the pulp, the improvement which consists of using as the collector for the impurities a refined low rosin tall oil product containing 1 percent to 5 percent by weight rosin acids and the balance substantially a mixture of oleic acid and linoleic acid, said low rosin tall oil product also serving to provide controlled frothing characteristics, said low rosin talloil product being the sole flotation oil added to the pulp.

2. The method of claim 1 wherein the rosin acid content is within the range of Z'percent to 4 percent by weight.

3. The method of claim 1 wherein the flotation is carried out in the presence of added minus 325 mesh calcite particles to aid in the flotation of the titania impurities and said tall oil is used in amount within the range of 5 to 10 lbs./ton of clay in the flotation pulp.

4. The method of claim 3 wherein said fine size fraction is about percent by weight less than 2 microns.

5. The method of claim 4 wherein the pulp containing the impure fine size fraction of clay and calcite is conditioned in a single stage with said tall oil.

t i I! I

Claims (4)

1. 2. The method of claim 1 wherein the rosin acid content is within the range of 2 percenT to 4 percent by weight.
2. 3. The method of claim 1 wherein the flotation is carried out in the presence of added minus 325 mesh calcite particles to aid in the flotation of the titania impurities and said tall oil is used in amount within the range of 5 to 10 lbs./ton of clay in the flotation pulp.
3. 4. The method of claim 3 wherein said fine size fraction is about 90 percent by weight less than 2 microns.
4. 5. The method of claim 4 wherein the pulp containing the impure fine size fraction of clay and calcite is conditioned in a single stage with said tall oil.