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UNITED STATES PATENT OFFICE 2,244,325 -COLLOIDAL SOLUTIONS of INORGANIC OKDES Paul G

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UNITED STATES PATENT OFFICE 2,244,325 -COLLOIDAL SOLUTIONS of INORGANIC OKDES Paul G 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, sodium, 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 sodium hydroxide. 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 acid, 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 sulfuric acid 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 sodium silicate 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 Sodium oxide, 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.
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