USRE14583E - Botho schwerin - Google Patents

Description

UNITED STATES BOTHO SGI-I'W'ERIN, F FRANKFORT-ON-THE-MAIN, GERMANY.

PATENT OFFICE.

METHOD OF SEPARATING SUBSTANCES IN SUSPENSION BY WASHING.

Specification of Reissued Letters Patent.

Reissued Jan. 7, 1919.

N0 Drawing. Original No. 1,029,579, dated June 11, 1912, Serial No. 646,746,1iled August 29, 1911. Application for reissue filed February 11, 1913. Serial No. 747,812.

To all whom it may concern Be it known that I, BOTHO SOHWERIN, a subject of the Emperor of Germany, and a resident of Frankfort-on-the-Main, Germany, have invented certain new and useful Improvements in Methods of Separating Substances in Suspension by Washing, of which the following is a specification.

The present invention'relates to an improved method of treating a composite mass or body held in suspenslon in a liquid so that the component parts thereof may be separated one from another.

As experiments in the subject of colloidal chemistry have shown, a large number of substances in colloidal condition can be brought into finely divided condition in suspension in water orin other liquids. Practical experience in the treatment of such material suspended in water has shown that such material acts as though it were charged with electricity, the charge, in some instances or with certain substances, appearing to be negative and in others positive as compared with the water.

It is now known that sedimentation of the whole mass suspended in the liquid can be obtained and the liquid may thus be clarified by the use of the following methods.

By one of these methods the material may be coagulated and sedimented by being mechanically adsorbed or held by some precipitate which is produced in the liquid containing the suspended matter, such as might be done, for example, by producing a calcium carbonate precipitate in water in which silica was suspended. The other method causes sedimentation or coagulation of the whole slime by neutralization of the electrical charges, which neutralization of charge can be brought about in several ways. For instance, sedimentation of a suspended matter of electronegative character may be effected by adding to the suspension a suspension of an electropositive body. It s also well known, that coagulation and sedimentation of the whole suspended matter may be obtained by adding to the suspen sion a suitable electrolyte, which will contain positive ions of salts if the matter in suspension is of an electrone ative fna-ture andnegative ions if, on the ot er hand, the suspension is of an electroposltive character.

As a precipitating agent'hme is also most extensively used where the precipitating effect is required for sedimentation of a suspended matter and clarification of the liquid. It has been found that if milk of lime is introduced into the tailings launder it neutralizes the free acid and precipitates the dissolved metallic salts as fiocculent hydroxids. These flocculae catch up the small particles of alumina and silica, and carry them down, leaving the water clear.

By using these methods it is intended in every case to eifect coagulation and sedimentation' of the whole suspended matter and clarification of the liquid containing the suspended matterr The purpose and efiect of the method hereinafter described is, how ever, clearly distinguishable from that referred to.

There are many substances which are of a composite character and in which the connection between the particles of different nature is so close that it is diflicult or impossible to effect a separation of the single components building up the substance in question. It has been demonstrated that according tothe prevailing conditions, cer- -tain parts of the material suspended in a liquid can be deposited more or less quickly while another part of the material remains in suspension and cannot be precipitated, or only so after a very long time. Those particles, which, under favorable conditions are first of all precipitated are .called gels while those particles remaining in suspension are called sols. Now it is known that surrounded to a certain extent by particles remaining in suspension and prevented from settling.

The object of the present invention is a method which enables both the gels and the sols to be obtained'quickly and cheaply from a slime and to separate these two classes from a slime, easily and with certainty by a perfect decomposition of the coagulated or composite substance in suspension, separating both the gels and the 1110 sols and precipitating totally and quickly the gels and retainin on the other hand in suspensionthe constituents which shall remain in solcondition.

The process is'therefore especially suit- 1 able for the commercial purification and separation of mixtures of finely divided bodies in suspension or in colloidal form. To mention an example, by the present method clay and kaolin having impurities such as sand, iron pyrites and the like, can

be commercially purified. Furthermore the matter will remain suspended in sol-co'ndition. The other portions of the composite matter, however, are deposited.

The portion of the suspended matter which will remain suspended is determined by the effective ionsof the electrolyte added.-

Thus, on the addition of a basic or so called felectropositive electrolyte, such as caustic soda, the effective ions are the negatively charged hydroxyl ions and they will cause increased dispersion and continued suspension of electronegatively charged particles and coagulation of electropositively charged particles.

For example, if the substance in suspension isa mixture of an electro-negative clay and an indifferent or electropositive body,

as for instance iron ore, the addition of an electrolyte of electropositive or basic nature,

for'instance hydroxid of sodium, will con-- vert the clay into such a condition that the particles thereof will be retained in suspension in sol-condition. Under the microscope 1ntense Brownian-movements of such particles can be observed. The particles of the oppositely charged iron ore, however,

will not be agitated but rapidly separated from the clay'and deposited. Or again, if the substance be a mixture of fine particles of clay and sand the addition of a, solution of. ammonia will effect a rapid separation of the sandfrom the clay, causing the sandto be precipitated while retaining the fine particles of clay in suspension. V The substance separated from the suspension by the method described can withconsistin suspends in 20 liters of water only requires drawn fromthe liquid and the matterremaining in suspension subsequently recov' ered and treated if desired. I

The amount of electrolyte required for the above described process is extremely small. For instance 10 kg. of a substance of a mixture of clay, sand, etc,

five cubic centimeters of a 25%-soluti on of ammonia. This extremely small quantity ofammonia is suiiicient for separating" the sand from the fine clay.

Finely divided substancesv are sometimes more or less indifi'erently afl'ect'ed by the action of electrolytes and the addition of such electrolyte alone is not sufiicient to effect the result hereinbefore described. 'I have found that such substances may be made electrically active by causing them to adsorb colloidal substances of a strong electropositive or electronegative character; As examples of substances of this character, hereinafter referred to as non-neutral colloidal-bodies, may be noted humic acid, silicic acid, aluminum hydroxid, etc. By the aid of such a non-neutral body the action of the proper electrolyte upon the otherwise indifferent substance will be as described when referring to substances which are naturally either strongly electropositive or electro-negative in character.

For example a suspension of indiiferent clay is mixed with a small quantity of humic acid. After a short time an electrolyte con-v taininghydroxyl-ions, such as for instance caustic soda in solution, is added in small quantities. The suspension passes gradually over into the sol-state, and the foreign particles, which are not in the sol-state, are precipitated. w

The same effect may be obtained, if soluble colloidal silicic acid is added to a suspension of indifi'erent clay, and thereafter adding caustic soda in solution.

One can also proceedin the opposite mannor by adding firstly caustic soda in solution and thereafter the soluble colloidal silici'c acid. The same efl'ect may be also obtained in solution is strongly hydrolyzed and contains hydroxyl ions and silicic acid. The

silicic acid is absorbed by the mass which is -1n suspension, whilefthe alkali having the property of a suitable electrolyte soon causes the sol-state. The quantity of electrolyte added is also extremely small. i

For instance with the aforesaid example it is sufficient to add to 1000 parts of clay,

suspended in water, about one part of soluble colloidal silicic acid and about one part of'caustic sodain order to attain the purification of clay. p I am aware that heretofore acids and alkalis have been added to substances for a various purposes but believe myself to be the first to have employed an electrolyte for the tegration or ing the suspended. matter,

salts or alkalis or lime have been added to peat to improve the quality thereof and soda as been added to faience, porcelain or chamotte in order to bring the material into proper condition for molding. It has also een recognized that finely divided substances are made more adaptable for suspension by adding thereto suitable electrolytes and that such electrolytes have been added to substances held in suspension to coagulate and precipitate such substances wholly, for the purpose of clearing thewater or recoveror both. It will be observed, however, that the method hereinafter claimed does'not involve the coagulation of suspended matter for the purpose of precipitating it but rather on the contrary a dissolution of coagulation, disinbreaking up of a composite or coagulated substance into its component parts andv causing one of said parts to be retained in suspension, while another separates therefrom and precipitates.

The method claimed is also clearly distinguished from those heretofore proposed for arating substances held in solution by w at may be termed a suspension process. In such a process use is made of a layer of suitable material, such as a soap solution, fat, oil, etc., which is relatively lighter than the body of water to which itis applied so that it will float thereon, and this floating body suspends and retains the finer particles while the others pass therethrough. By such suspension process the character of the floatin layer or separating body does not depen upon the electrolytic nature of the material treated, as in the present invention, but" may be of the same character, for example a soap solution, whether the component of the material treated that is to be retained in suspension is of electro-negative or electro-positive nature. Examples of this are found in the patents to Ivery, 667,222, where a soap is used to retain an electronegative clay in suspension, and in the patents to Cartwright, 980,143 and 988,692, where soap is used for the same purpose with eleCtro-positive metal oxid.

What I claim is:

1. The herein described method of separating a composite mass containing oppo-- sitely charged particles suspended in a liquid which cons sts in adding to the liquid and not those 0 an electrolyte containing ions of an electrical character which is the same as the character of the part of the composite mass which it is desired shall remain in suspension in sol-condition and permitting the part thereof having opposite electrical character to de osit. I

2. ihe herein described method of separating a composite mass suspended in a liquid which consists in addin to the liquid a strongly non-neutral colloi a1 body and an electrolyte containing ions of an electrical character which is the same as the character of the part of the resulting composite mass which it is desired shall remain in suspension in sol-condition and permitting the part thereof having opposite electrical character to deposit.

3. .he process of separating the ingredients of a mixture which consists in suspending said mixture in a suitable liquid medium, the ingredients of said mixture thereby acquiring unlike electrical charges, and adding to the suspension an yielding ions weaken the char es on particles of one sign n g the other sign and thereafter separating the former particles, which are deposited from the latter, which remain suspended.

' 4, The process of purifying impure clay which consists in suspending in water the clay containing impurities having an opposite electrical sign when thus suspended, and adding thereto an alkaline electrol te adapted to neutralize the charges on the impurities to causethe clay to be retained in suspension and the impurities deposited.

5. The process of '-'purifying impure clay which consists in suspending in water the clay containing impurities having an opposite electrical sign when. suspended, adding thereto a minute amount of dissolved sodium hydroxid, and permitting the suspension to remain at rest, whereby the clay particles are retained in suspension and the impurities deposited.

In testimony whereof I aflix my signature in presence of two witnesses.

BOTHO SGHWERIN.

Witnesses J EAN GRUND, CARL GRUND.

electrolyte adapted to neutralize or