US2018987A - Process of preparing active bleaching clays - Google Patents

Description

Patented Oct. 29 1935 PATENT OFFICE PROCESS or PREPARING ACTIVE BLEACHING CLAYS Anton Winmiiller, Heui'eld, Oberbayern, Germany, .assignor to Bayerische Aktiengesellschaft i'iir Chemisch'e & landwirtschaftlichchemische Fabrlkate, Heuield,

Germany Oberbayern,

No Drawing. Application August 17, 1932, Serial No. 629,241. In Germany September 3, 1931 Q Claims.

It is well known to produce bleaching powder by forming a muddy suspension of raw clays in water, adding hydrochloric or sulphuric acid and boiling the mixture for an extended length of time by the introduction of steam. The quantity of acid used in this process is dependent upon the property and dryness of the resulting sediment. After boiling the mixture, it is filtered and the solid residue washed, dried and ground. The filtrate liquor is either discarded as waste or treated for the recovery of its valuable constituents.

It has also been suggested to prepare bleaching-clay by mixing raw clay with sodium-chloride and treating the mixture with sulphuric acid.

It is further known to produce bleaching-clayby reacting sulphuric acid or a bisulphate or a mixture of the two with raw clay, whereupon the mixture is partially or entirely dried.

It is further known, to treat natural chinaclay without washing or grinding the same with concentrated hydrochloric acid or an acid-forming salt or a mixture .of acid and salt. In this manner a stable granular bleaching powder may be produced.

In addition, it has been suggested to treat raw clay by means of free acid and by the application of the counter-current principle in a series of treating vessels in such a manner, that the raw material is fedin at one end of the plant and the necessary decomposing acid on the other end, so that the clay and acid are forced through the apparatus on the counter-current principle, whereby the acid will be gradually consumed and the soluble salts of the raw clay will gradually be leached out, so that finally the lixiviated earth can be removed and further treated, while the exhausted acid is withdrawn at the other end and discarded as non-usable waste. Obviously this method of operation leads to very eflicient results.

In all the above-outlined processes, the quantity of acid proportional to the raw material consumed is substantially constant where the resulting bleaching power of the product is equivalent. Prior to the present invention it was taken as granted that in order to obtain a prodnot .of the highest bleaching power, all the acidsoluble constituents must be removed from the raw material. Obviously, therefore, the quantity of acid theoretically necessary will always be n that amount necessary to dissolve the acid-solu-= ble constituents from the raw materials, whether operating with the reactants flowing in the same direction or counter-currently.

I have now discovered that it is possible to produce a bleaching powder of fully equal bleaching power by using less than the theoretical amount of acid necessary to dissolve the acid-soluble constituents from the raw clay. Furthermore, by the use of my new process the quantity of acid which is used is substantially completely utilized and the yield of bleaching powder is increased. vI obtain these results by following the procedure of the known water suspension and boiling method as above set forth with ,the additional procedure of introducing certain salts of the acid used, prior to or during the boiling period, and using a much smaller amount of the acid.

When using hydrochloric acid, for instance, it i was possible to save about one third of the former consumption, if in lieu of the saved hydrochloric acid suiiicient quantities of sodium chloride or potassium chloride are added. Likewise, it was found, that upon using ferric and aluminium chloride, or the chlorides of the alkaline earths a substantial saving in acid was rendered possible, the extent of which is dependent on the quantity and concentration of the chloride added, each time. If sulphuric acid is used as decomposing agent the corresponding sulphates I must be added.

It was further found, that a saving in acid of this nature is not only possible by using the above-mentioned salts and their compounds, but that such saving may also be efiected, if the waste liquors of the known boiling process or the boiling process according to the present invention are employed instead of the salts mentioned. The waste-liquors, depending upon the composition and condition of the raw materials used, contain besides slight quantities of free acid mainly aluminium salts as well as varying quantities of ferric salts,-alkaline earth salts and alkaline salts of the acid employed each time.

It has proved suitable to employ during the lixiviation by means of hydrochloric acid the waste-liquors of acorresponding preceding hydrochloric acid lixiviation and upon use of sulphuric acid the waste-liquors of a corresponding preceding sulphuric acid decomposition, so that with an emcient application of the process the liquor may be used in a cycle, which can. be repeated at wili.

The process according to the invention is carried out as follows:

The raw earth is diluted, either, as formerly with water by adding simultaneously or subsequently thereto, one or-several of th'esalts mentioned or by adding one of the. waste iiquors 55 mentioned, or, by employing a corresponding mixture respectively. Preferably the preparation proper of the aqueous muddy suspension is already effected with the salt solutions or wasteliquors, in order to avoid the unnecessary dilution through the depositing water.

The quantity of acid added depends upon the kind and quantity of salt solutions or waste-liquors used. Naturally the saving in acid is entirely dependent upon the kind of raw clay, and the quantity and quality of the salt solutions or waste-liquors used. Even in the most unfavorable instance it is still possible to get along with considerably smaller quantities of fresh acid than such was necessary according to the former method, for obtaining an equally effective bleaching power.

Apart from this, the output of highly active bleuhing-clay is considerably increased through this new method of lixiviation, which will also play an important part as regards the price of the product. In all those cases, however, where no great importance is attached to a saving in acid and an additional output oi bleaching-clay, and where it is desired to proceed with the quantitles of acid customarily used, it is nevertheless suitable, to employ additional salt solutions or waste-liquors respectively, since by such procedure the essential advantage is gained'that the waste-liquors are obtained in a concentrated form and may thus be employed more easily for further work.

Naturally the waste-liquors obtained by the new process will gradually become rich in dissolved ingredients .as regards their 'content (salts of aluminium, iron, of the alkaline earths and alkalies), so that it is necessary for the elimination of excessive concentrations, to bring these wasteliquors back to the desired concentration, suitably by the addition of the washing water of the filtered material, after they have been employed once or several times. I

(1) Example of operation under the previously knpwn boiling processwitn acid:

.moist state as it comes from the pit containing ll40kilograms of dry substance, are reduced to mud with-1420 litres of water, whereupon the '.-material is mixed with 1260 litres of hydrochloric acid oi. 18 Be. 36 kilograms of, hydrochloric acid per 100 kilograms of drysubstance), then boiled and further. treated in known manner.

The output amounts to-"7-8.5 per cent of the dry substance used.

(2) Examples of operation under the improved process:

(a) 2000 kilograms of raw earth employed in the moist state as it comes from the mine, containing 1140 kilograms of dry substance, are reducedto mud with 1420 litres of a solution of chloride of aluminium of 10 1%., whereupon the material is mixed with 700 litres of hydrochloric acid of 18 B. 20 kilograms of hydrochloric acid per 100 kilograms of dry substance), then boiled and further treated in known manner.

The output is 82 per cent of the dry substance employed, having an equally effective bleaching power as the bleaching clay obtained according to Example 1.

(b) 2000 kilograms of raw earth in the moist state as in Examples 1 and 2a, containing 1140 kilograms of dry substance are reduced to mud with 1420 litres of a. waste-liquor of 10 B. obtained from a preceding boiling process, where upon 700-litres of hydrochloric acid of 183 B. are added 20 kilograms hydrochloric acid per 100 kilograms of dry substance), then the mass is boiled and further treated in the usual manner.

The output likewise amounts to 82 per cent of the dry substance employed, having an equally effective bleaching power as the bleaching-clay obtained according to Example 1.

I claim:

1. Process of activating bleaching clay material comprising suspending the clay material in an aqueous solution of a salt, adding to the suspension a quantity of free acid oi said salt, and boiling the acidified suspension until the acid is completely used, whereby the acid treatment is effected entirely in the presence of salts of said v acid.

2. Process of activating bleaching clay material aqueous solution of a chloride, adding to the suspension a quantity of hydrochloric acid, and boiling the acidified suspension until the acid is completely used, whereby the acid treatment is effected entirely in the presence of salts of said acid.

3. Process of activating bleaching clay material comprising suspending the clay material in an aqueous solution of a sulfate, adding to the suspension a quantity of sulfuric acid, and boiling the acidified suspension until the acid is completely used, whereby the acid treatment is etfected entirely in the presence of salts of said acid.

4. A process as defined in claim 1 wherein the aqueous salt solution is the liquor from a previous acid treatment of the clay material.

ANTON wIRzMfILLEa;