Patented June 3, 1941 2,244,325

UNITED STATES PATENT OFFICE 2,244,325 -COLLOIDAL SOLUTIONS OF INORGANIC OKDES Paul G. Bird, Western Springs, Ell. No Drawing. Application April 15, 1940, Serial No. 329,29 9 Cains. (C. 252-313) The present invention relates to an improve ment in the manufacture of highly reactive col Such as, for example, , but in which the loidal solutions of inorganic oxides. ratio of SiO2 to Na2O is at least 10:1 and may One of the primary objects of the present in be as high as 100:1 but preferably is about 50:1. vention is the production of colloidal solutions of A further object of the invention is to produce, 5 in accordance with the broad principles of the inorganic oxides which are normally considered invention, a coagulant or reagent which may be as being substantially insoluble in water. These employed, for example, for the treatment of wa oxides may be metallic, nonmetallic or those of ter, particularly for clarification of turbid wa an element that has properties intermediate ter, Sewage effluents, and the like, consisting of those of metals or nonmetals. In essence, the 10 a colloidal dispersion of silica having a concen invention is concerned with the treatment of a tration of from 5% to 15% of SiO2 kept in solu soluble salt, the anion of which consists of Oxy tion by a very small amount of . gen and another element, the latter being in : A further, and more specific, object of the state of oxidation in which it is predominantly invention is a process for producing a colloidal , and the acid and oxide of which are rela silica solution bypassing a dilute alkali silicate tively insoluble. Solution through a mass or bed of a zeolite or The underlying principle upon which the pres ion-exchange material for the purpose of remov ent invention is predicated involves the passage ing from the silicate solution the alkali metal of a solution of an alkali compound of an ele ions as far as possible, so that the effluent from ment over an acid-regenerated Zeolite or ex 20 the process Will contain a large proportion of col change material whereby the alkali is Substan loidally dispersed SiO3, only a small amount of tially removed from the compound, leaving the alkali metal hydroxide, and very little, if any, oxide of the element in Solution in the colloidal Other ions or electrolytes. It has been found that state. After the zeolitic material has adsorbed to carry out the present invention it is particu its quota of alkali, it can be restored or regener larly advantageous to employ for that purpose a ated by the expedient of passing an acid Solution carbonaceous Zeolite; that is to say, ion-exchange over it, thereby forming a soluble alkali com materials derived from, for example, cellulosic pound, which may then be washed from the Zeo material such as wood which has been treated litic material, whereafter the latter may be em With concentrated under conditions ployed for treating new amounts of the alkali 30 conducive to the production of a material hav compound of the said element or other analo ing high exchange properties. Such materials gous compound Or Compounds. are sufficiently well known in the art of making The term 'zeolite' is used in the present con exchange materials to require no further descrip nection in its generic sense of any exchange ma tion herein. These carbonaceous exchange ma terial, be it either natural or Synthetic, inor terials will exchange metallic ions such as sodium ganic or organic in nature. or potassium ions from a dilute solution of a The present invention, as will be shown in silicate, leaving the silica itself remaining in the greater detail hereinbelow, may be applied to Water in the form of what is believed to be a a large number of substances, and is generic in colloidal Solution. After the carbonaceous zeolite its nature. Thus it may be applied to the pro 40 has been exhausted of its exchange properties it duction of colloidal solutions of silica (silicon is capable of being restored to substantially its dioxide, SiO2), tungstic acid, molybdenum tri Original activity by appropriate treatment with oxide, antimonic acid, vanadium oxide or vanadic an acid in accordance with the manner herein- : acid, germanium oxide, and the like. For in after described. It is, of course, possible to use stance, a solution of may be any other kind of Zeolite which has the capacity passed through, or otherwise contacted with, a of taking up metallic ions. The primary object mass of acid-regenerated zeolite, resulting in the of employing a Zeolite is to remove the alkaliions, adsorption of the sodium ion from the Sodium Such as the Sodium ions, from an alkali silicate silicate by the zeolite, yielding a colloidal Solu Such as, for example in this instance, sodium tion of silicon dioxide (silica, SiO2). silicate, The invention may with great advantage be In one of its preferred embodiments the pres applied to the production of a highly reactive ent invention comprises diluting a commercially colloidal solution or aqueous dispersion of silica, obtainable sodium silicate solution to about one SiO2, probably in the form of Si(OH)4, with, how tenth of its original concentration and then pass ever, a small residuary amount of an alkalimetal 55 ing the diluted Solution through a mass or bed 2 2,244,325 of an appropriate zeolite, collecting the effluent for commercial purposes a ratio of 50:1 is quite in a tank or reservoir and continuing the process satisfactory. until toward the end of the operation the effluent After the passing of the sodium silicate solu from the zeolite bed begins to react decidedly tion through the zeolite has been stopped the alkaline. The combined effluent is titrated from ed Zeolite is regenerated as follows: It is first back time to time with acid until it reaches a prede Washed with plain water to wash therefrom the termined alkalinity, whereupon the process is thereto adhering sodium silicate and is then stopped and the entire collected effluent is either treated with a dilute solution of sulfuric acid, sold as such or further concentrated, as by evap using about 3 pounds of 66° Baumé sulfuric acid oration. Thereafter the zeolite is regenerated to per cubic foot of zeolite, whereafter the acid is re be made ready for further use. moved and the zeolite washed with water to re Purely as an exemplification of the present in move the \excess acid and the sodium sulfate vention and without in any way intending to lim which has been formed as a result of the action it it thereby, details of a commercially feasible of the acid upon the zeolite. After the acid has operation for the production of a colloidal silica thus been washed out, the zeolite is ready to be solution will now be presented. For example, used for the production of a further batch of 27.5 gallons of what is known as 'JM brand' so silica Solution of the present invention. The sul dium silicate are diluted with Water to form a furic acid is preferably used in a concentration total of 275 gallons of solution. The JM brand of about 4% of actual HaSO4. sodium silicate has a density, at room tempera 0 During the first part of the operation the ture, of 42' Baumé, which is equal to a specific effluent flowing from the zeolite is practically gravity of .417 at 70 F. and Contains approxi neutral in reaction and contains only a very mately 29.6% of silica and about 9% of alkali small amount of sodium or other alkali ion, and calculated , as , Na2O. In other it is within contemplation of the invention to words, it is, roughly, a 30% solution expressed segregate this first portion to form a particularly as SiO2. The diluted Solution therefore Will con pure form of the product of the present inven tain one-tenth, or approximately 3%, of SiO2. tion. In this product the ratio of SiO2 to NaO The material is, of course, not present at that may be as high as from 75 to 100:1. stage as actual SiO2, nor is the alkali there as When such a colloidal silica solution is em actual Na2O, the two materials undoubtedly be ployed, for example, as a coagulant for turbid ing in combination in the form of a complex Waters, sewage effluents, factory waste waters, silicate or silicates, but it has been customary in etc., a Solution of a ratio of about 50:1 has been this art to express the compositions of these sili found to be quite satisfactory and sufficiently cate solutions in terms of the ratio between inexpensive to warrant large-scale use. the silica SiO2 and the alkali as sodium oxide or The appearance of the colloidal silica solution Na2O. In this particular brand of silicate the of the present invention is a relatively clear so ratio is SiO2:Na2O=3.3:1. This ratio is, of lution, although it may possess a slight turbidity. course, not at all disturbed by the dilution of It is practically free of chlorides and contains the solution. This dilute Solution is then passed but a very slight amount of sulfate ion, and the through an acid-regenerated bed of a carbonace only electrolytes present in Substantial amounts ous zeolite composed of, for example, 20 cubic are residual Sodium silicate and a small amount feet thereof, the rate of passage being approxi of sodium hydroxide. mately one gallon per Square foot per minute. If ordinary non-carbonaceous zeolites are em The effluent is collected in a large container un ployed for this purpose, the regeneration with acid must be accomplished with care in order to til the alkalinity of the entire amount of collected avoid destroying the zeolite. It is, of course, ob material, as measured by titration thereof with vious that the sulfuric acid described in the par acid to the methyl Orange end point, reaches ticular example of regeneration may be replaced from 60 to 75 grains per gallon calculated as by any other acid, such as a mineral acid or an CaCO3, at which time the further flow of solu . Suitable are hydrochloric tion through the carbonaceous Zeolite is stopped. acid, , acetic acid, oxalic acid, etc. It The resultant solution Will then have a silica Will, of course, also be possible to start with some content of about 3 to 3.5%, which is the same other alkali silicate, such as potassium silicate, as it was before, but practically all of the Na2O lithium silicate, etc., although, obviously, these content will have been retained by the Zeolite. would be very much more expensive and hence, In order to reduce the amount of liquid which from a commercial point of view, not as desir is to be sold and shipped, it has been found ad able; but the invention is not limited to any par vantageous to evaporate the total effluent, pref ticular alkali silicate, nor to any particular erably in a vacuum evaporator, to about one-half Zeolite, nor to any particular acid for regenera its original bulk, which therefore raises its Silica tion of the zeolite. content to about 6 to 6.5%. A typical analysis 60 The colloidal silica solution thus prepared of the Silica Solution prepared according to the forms an excellent coagulant for water and sew just mentioned example is about 6.5% SiO2 and age treatment. 0.13% Na2O, which has a ratio of SiO2 to Na2O When applying the present invention to the of exactly 50:1. In other Words, there is about 65 preparation of other colloidal oxide or acid so fifteen times as much silica per unit of sodium lutions, the procedure is quite similar. As fur oxide in the finished product as there was in ther examples, the following are cited: the original sodium silicate Solution. A solution of sodium tungstate (NaWO4.2H2O) While it is desirable to remove as much of Was made in Water solution to give a strength of the alkali as possible, a very small amount of it Sodium oxide of 0.5%. When this solution was should be allowed to remain in the product, as passed through a zeolite bed which had been it greatly enhances its keeping qualities, prevent previously treated with acid and washed free of ing it from congealing Orgelling. the acid, it was found that the effluent from the It is possible to produce Solutions containing Sodium tungsate solution was fluorescent under a ratio of SiO2 to Na2O of as high as 100:1, but 75 a blue light, was slightly cloudy, and had the

2,244,825 3 Tyndall effect, indicating the presence of col tion of an which comprises the steps loidal matter. When this liquid was evaporated of treating a carbonaceous zeolite with an acid the residue was found to consist of approximate and then contacting an aqueous Solution of an ly 99% tungstic acid and 0.5% Na2O, The ef alkali compound of said oxide therewith, where fluent Solution Was acidic, equivalent to 96 grains by the alkali metal ions of the latter Solution per gallon in terms of calcium carbonate, where will be adsorbed by said zeolite, leaving the ox as the influent had an alkalinity of 295 grains ide in colloidal solution. per gallon in terms of Calcium carbonate, 4. The process of producing a colloidal solu Sodium molybdate (Na2MoCl4.2H2O) was made tion of silica, which comprises passing a solution up in Solution in such strength that it contained 0 of an alkali silicate through a mass of ion-ex 0.5% Na2O. When this was passed through an change material which has been treated with an exchanger bed which had been previously treat acidic reagent. . . . ed with acid and washed free of the acid, it was .5. The process of producing a colloidal solu found that the effluent coming through was a deep tion of silica, which comprises abstracting the blue color, and the influent was colorless. The alkali metal ions from an alkali metal silicate colloidal solution produced was perfectly clear Solution by exchange effected by means of and stable, and showed no tendency to settle out a zeolite which has been treated with an acidic after a period of several weeks. It was concluded reagent. that a molybdenum oxide complex was probably 6. The process of producing a colloidal solu formed. Upon evaporating the effluent the resi 20 tion of silica, which comprises the steps of treat due was found to consist of 99% molybdenum tri ing a carbonaceous zeolite with an acid and then oxide (MOO3) and approximately 0.5% Na2O. contacting an aqueous solution of an alkali sili In like manner potassium pyroantimonate cate therewith, whereby the alkali metal ions of (Ka2Sb2O7.4H2O) was passed through a bed the Silicate solution will be adsorbed by said zeo prepared as above. The alkalinity of the influ lite, leaving the silica in solution. ent was 37.6 grains per gallon in terms of cal 7. The process of producing a stable colloidal cium carbonate, while the effiuent had an acidity Solution of silica, which comprises diluting an ap equivalent to 63 grains per gallon in terms of cal proximately 30% solution of sodium silicate hay cium carbonate. It was also found, however, ing an SiO2 to Na2O ratio of about 3:1 to about due to the low solubility of this salt, that SOme one-tenth of its original concentration and then what less than 0.4% sodium oxide was in the in , 30 passing the diluted solution through a mass of fluent. The effluent was slightly fluorescent and carbonaceous zeolite to abstract sodium ions cloudy, showed the Tyndall effect, and no set therefrom, collecting the effluent and continu tling took place on standing. ing passing the solution through the zeolite un A Solution of sodium vanadiate was passed. til the total collected effluent has an alkalinity through a zeolite bed as described above and as determined by acid titration of about 50 to was found to yield a colloidal solution of vana 5 grains per gallon (calculated as CaCO3) and dit.m. oxide. The effluent was colored yellow and then evaporating the combined effluent to about lupin being evaporated to dryness resulted in a one-half of its volume. green powder. The colloidal solution of vanadium 8. A cyclic process of producing a colloidal oxide was relatively stable. 40 Solution of an acidic oxide which comprises paSS Sodium germanate was made up into solution ing a dilute solution of an alkali compound of an to contain 20 grams per liter of germanium ox acidic oxide through a mass of an ion-exchange ide (GeO2) and passed through a zeolite bed pre material to abstract alkali ions therefrom, col pared as above, and the effluent was found to lecting the resulting effluent, continuing the Op give the Tyndall effect, showing the presence of 45 eration until the effluent contains the maximum colloidal germanium oxide. desired alkali-ion content, then backWashing the The colloidal Solutions thus prepared are fair mass of exchange material to remove the there. ly stable, particularly if a small amount of al to adhering. Solution of the alkali COmpOund of kali be allowed to remain therein. They may the acidic oxide and thereupon treating it with be employed for any purpose for which they 50 'a dilute acid to regenerate its exchange power may be suitable. When mentioning alkali, a.m. and Washing is free from acid, and then again monium is to be considered as included. In gen passing a dilute solution of the alkali COrlpound eral, the process may be said to comprise the of an acidic oxide through the exchange nate production of a solution of the oxide of an ele 3. ment whose oxide is predominantly acid and 55 9. A cyclic process for producing an aqueous hence capable of forming salt-like compounds Solution of an inorganic acidic Oxide normally withObvious the alkalis. equivalents, within the knowledge of insoluble in water which comprises passing a the skilled chemist, are to be construed as with dilute solution of an alkali COrlpound of such in the Scope and purview of the present inven 6 an oxide through a mass of ion-exchange ma tion, for which the inventor claims: terial which has been treated With an acidic re ... i. The process of producing a colloidal solu geot So as thereby to extract alkali ions from tion of an acidic oxide which comprises passing Said alkali compound, collecting the resulting 8. Solution of an alkali salt thereof through a efluent, continuing the operation until said mass of ion-exchange material which has been 65 effluent contains the desired alkali-ion content, treated with an acidic reagent, then backWashing the mass of exchange mate rial to remove the thereto adhering Solution of the 2. The process of producing a colloidal solution alkali compound of the oxide, thereupon treat of an acidic oxide which comprises abstracting ing it with a dilute acid to regenerate its ex the alkali metal ions from an alkali metal.com change wer and Washing it free from acid, pound thereof by base exchange effected by O then again passing a dilute solution of Said al anmeans acidic of areagent. 2eolite which has been treated with kali compound of Said inorgani 3. The process of producing a colloidal solu the exchange material. ganic oxide through FAU, G. BIRD,

CERTIFICATE OF CORRECTION. ... Patent No. 2,244,325. June 3, 194l...... PAUI, C, BIRD. It is hereby certified that error appears in the printed specificationa of the above numbered patent requiring correction as follows: Page 5, séc ond column, line 51, claim 8, for the word "is" read --it-- and that the said Letters Patent should be read with this correction therein that the it same may conform to the record of the case in the Patent Office. signed and sealed this 15th day of July, A. p. 1.9ll.

. . x . . . . Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

...... CERTIFICATE OF CORRECTION. . Patent No. 2,244,325. w . . June 3, 1941...... PAUL G. BIRD. It is hereby certified that error appears in the printed specificationa of the above numbered patent requiring correction as follows: Page 5, séc ona column, line 51, claim 8, for the word "is" read --it- and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. signed and sealed this 15th day of July, A. P. 1941.

“. . . . . k . . . . . ; Hemry Van Arsdale, (Seal) Acting commissioner of Patents.