GB1586545A - Creation of Inventions and Patents with Artificial Intelligence

GB1586545A – Process for purifying water containing fluoride ion
– Google Patents

GB1586545A – Process for purifying water containing fluoride ion
– Google Patents
Process for purifying water containing fluoride ion

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Publication number
GB1586545A

GB1586545A
GB2864/78A
GB286478A
GB1586545A
GB 1586545 A
GB1586545 A
GB 1586545A
GB 2864/78 A
GB2864/78 A
GB 2864/78A
GB 286478 A
GB286478 A
GB 286478A
GB 1586545 A
GB1586545 A
GB 1586545A
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United Kingdom
Prior art keywords
fluoride
water
calcium
phosphate
composition
Prior art date
1977-01-24
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)

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Application number
GB2864/78A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

Andco Industries Inc

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Andco Industries Inc
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1977-01-24
Filing date
1978-01-24
Publication date
1981-03-18

1978-01-24
Application filed by Andco Industries Inc
filed
Critical
Andco Industries Inc

1981-03-18
Publication of GB1586545A
publication
Critical
patent/GB1586545A/en

Status
Expired
legal-status
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Current

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Classifications

C—CHEMISTRY; METALLURGY

C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

C02F1/00—Treatment of water, waste water, or sewage

C02F1/58—Treatment of water, waste water, or sewage by removing specified dissolved compounds

C02F1/583—Treatment of water, waste water, or sewage by removing specified dissolved compounds by removing fluoride or fluorine compounds

C—CHEMISTRY; METALLURGY

C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

C02F1/00—Treatment of water, waste water, or sewage

C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities

C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents

C—CHEMISTRY; METALLURGY

C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

C02F1/00—Treatment of water, waste water, or sewage

C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities

C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents

C02F1/5245—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents using basic salts, e.g. of aluminium and iron

C—CHEMISTRY; METALLURGY

C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

C02F1/00—Treatment of water, waste water, or sewage

C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment

C—CHEMISTRY; METALLURGY

C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

C02F2101/00—Nature of the contaminant

C02F2101/10—Inorganic compounds

C02F2101/12—Halogens or halogen-containing compounds

C02F2101/14—Fluorine or fluorine-containing compounds

C—CHEMISTRY; METALLURGY

C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

C02F2209/00—Controlling or monitoring parameters in water treatment

C02F2209/06—Controlling or monitoring parameters in water treatment pH

Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC

Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

Y10S210/00—Liquid purification or separation

Y10S210/902—Materials removed

Y10S210/915—Fluorine containing

Description

PATENT SPECIFICATION ( 11) 1 586 545
f ( 21) Application No 2864/78 ( 22) Filed 24 Jan 1978 ( 31) Convention Application No 761685 ( 32) Filed 24 Jan 1977 in D ( 33) United States of America (US) ( 44) Complete Specification published 18 March 1981 ( 51) INT CL 3 C 02 F 1/58 ( 52) Index at acceptance CIC 210 253 254 31 X 461 C ( 54) PROCESS FOR PURIFYING WATER CONTAINING FLUORIDE ION ( 71) We, ANDCO INDUSTRIES, INC, a Corporation organised and existing under the laws of the State of New York, U S A of 2005 Walden Avenue, Buffalo, New York 14225, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following 5
statement:
This invention relates to the removal of fluoride from water and more particularly relates to its removal as a water-insoluble precipitate.
Many industrial processes including those processes for the manufacture of phosphates, fluoborates, fluorides, fluorine, and fluorosilicate have large quantities 10 of waste water which contain fluoride For the protection of the environment, it is necessary to remove fluoride ion from the waste water prior to its discharge.
Governmental regulations presently provide for limitations on the discharge of fluorides to the environment and generally require removal of as much fluoride as possible prior to its discharge 15 In the prior art, methods have been developed for removing fluorides from waste water None of these processes for removing fluorides have been completely successful since even the best of the commercially feasible processes result in the waste water continuing to contain at least about four parts per million and usually in excess of ten parts per million of fluoride 20 Generally, the prior art processes precipitated fluoride contained in the waste waters as calcium fluoride Such precipitation usually did not result in the removal of sufficient fluoride to drop the fluoride concentration in the waste water below eight parts per million When, subsequent to initial removal of calcium fluoride, large quantities of calcium compounds were added to the waste water, for example 25 in the form of lime, additional precipitate would form which would drop the fluoride concentration to as low as about four parts per million if long holding times were used.
No commercially feasible prior art process however, removed sufficient fluoride from the waste water to drop the fluoride concentration to below about 30 three parts per million A lower concentration of fluoride in discharged waste water is desirable for better protection of the environment.
The ocean has been able over long periods of time to free itself from many soluble fluorides and presently contains about 1 4 parts per million of soluble fluoride The ocean has been able to remove fluorides in the form of water 35 insoluble calcium salts, some of which have converted to highly insulable fluorapatite However, since three moles of phosphate are required for each mole of fluoride to form fluorapatite and since the ocean contains less than about 0 1 parts per million water soluble phosphate, the ocean is unable to remove the remaining soluble fluorides as fluorapatite 40 While the chemistry of the formation of fluorapatite from calcium, fluorine and phosphate has been intensively studied, we are unaware of any commercially feasible prior process utilizing the chemical mechanisms involved in the formation of fluorapatite and which is useful in the purification of waste streams which contain fluoride 45 According to the present invention there is provided a process for purifying water containing fluoride which comprises adjusting the composition of the water by providing sufficient available calcium and sufficient available phosphate to enable at least a portion of said fluoride to be precipitated as fluorapatite and if necessary adjusting the p H and in which a seeding composition selected from fluorapatite, calcium fluoride and mixtures thereof is dispersed into said waste water to act as a nucleating agent whereby a precipitate is formed containing essentially all fluoride initially present in the water Desirably, but not essentially, 5 the precipitate is separated from the waste water within about four hours and preferably within about two hours after essentially all of the fluoride is precipitated.
In accordance with the process of the invention any necessary calcium composition and phosphate composition are added to the water to provide the sufficient available calcium and phosphate The sufficient available phosphate and 10 sufficient available calcium may be added simultaneously or separately The phosphate and calciutn compositions may be added during preceding independent processes while the water is being used, or may be added after preceding independent processes have finished utilizing the water Usually, but not necessarily, the sufficient available calcium is incorporated into the water before 15 the incorporation of the available phosphate.
According to a preferred aspect of the invention, at least a portion of the fluoride is precipitated as fluorapatite, said fluorapatite is separated from said water and treated with acid to form calcium fluoride and water-soluble phosphate composition and said water-soluble phosphate composition is continuously 20 recycled as phosphate to additional water containing fluoride If the water already contains sufficient phosphate or calcium, additional phosphate or calcium need not be added For example, if the water already contains sufficient available calcium, e.g usually at least three and preferably at least five moles per mole of fluoride, additional calcium need not be added and in accordance with the invention it is 25 only necessary to add sufficient available phosphate.
Sufficient acid may be added to the water prior to or simultaneously with the adding of either the calcium or phosphate to obtain a p H below about 11 5 after both the calcium and phosphate are added.
Sufficient base may be added after the addition of calcium, phosphate and the 30 sufficient acid to obtain a sufficiently high p H to cause the formation of a precipitate The resulting precipitate is then maintained in contact with the water until essentially all fluoride is removed from the water.
“Available calcium” as used herein means calcium which is in solution or is otherwise available to react with fluoride and available phosphate to form 35 fluorapatite “Sufficient available calcium” means that amount of available calcium which in conjunction with available phosphate is required to precipitate essentially all of the fluoride and is usually at least three moles of calcium per mole of fluoride present in the water.
“Available phosphate” as used herein means phosphate ion or a watersoluble 40 phosphate composition having a phosphate radical available to react with fluoride to form fluorapatite “Sufficient available phosphate” means that amount of available phosphate which in conjunction with the available calcium is required to precipitate essentially all of the fluoride and is usually at least one mole per mole of fluoride in the waste water 45 “Fluoride” as used herein means fluorine in any form which will react with calcium ion and phosphate ion in water to form fluorapatite either directly or through intermediate compositions The fluoride is usually in the form of fluoride ion.
Waste water containing fluoride is purified before it is discharged to the 50 environment by removing fluoride “Purifying”, as used herein, means that essentially all fluoride is removed from the waste water “Essentially all” is intended to mean that less than three parts per million of fluoride remains in the purified water; however, by this process,_waste water can be readily obtained containing less than 0 5 parts per million (ppm) fluoride and under proper 55 conditions, less than 0 1 parts per million fluorides Purified waste water has even been obtained by this process which contains less than 0 005 parts per million fluoride.
As indicated, in accordance with the process of the invention, water is purified by removing fluoride in the form of a precipitate At least some of the precipitate is 60 believed to be fluorapatite which is a water-insoluble fluoride composition containing calcium and phosphate groups and is believed to have the formula:
Caj(P 04)1 F.
Fluorapatite, as can be seen from the above formula, is believed to have a 1.586,545 3 1,586,545 3 mole ratio of five moles of calcium to three moles of phosphate to one mole of fluorine and its formation may be represented by equation 1.
Equation 1 Ca 2 + 3 PO 4-3 +FF->Ca,(PO 4)3,F Equation 1 above, while representing the overall formation of fluorapatite 5 from calcium, phosphate and fluoride, does not necessarily require that the fluorapatite be formed by the direct interaction of the ions In some cases it is believed that intermediate compounds or species may be formed which subsequently convert to the fluorapatite.
A few of such intermediate compounds which are believed to be formed when 10 calcium, phosphate, fluoride ions are present in aqueous solution are:
Whitlockite or beta calcium phosphate having the formula P Ca 3 (P 04)2; Octacalcium phosphate having the formula Ca 8 H 2 (P 04) 51-20; Brushite having the formula Ca HPO 4, 21-20, and Monetite having the formula Ca HPO 4 15 In addition, it is believed that fluorapatite may be formed by conversion from amorphous calcium phosphates in the presence of fluoride.
In order to precipitate essentially all of the fluoride present in the waste water as fluorapatite, at least five moles of available calcium and three moles of available phosphate must be present in the waste water for each mole of fluoride The 20 presence of these appropriate amounts of calcium and phosphate are necessary to permit essentially all of the fluoride to precipitate in accordance with equation l; however, less than these amounts can be used to precipitate essentially all of the fluoride when a portion of the precipitate is a compound other than fluorapatite It has, for example, been unexpectedly found that essentially all fluoride can be 25 precipitated when a portion of the precipitate is a form of calcium fluoride.
Sufficient precipitation of fluorapatite formed from calcium, phosphate and fluoride in aqueous solution is dependent upon the p H of the solution The final p H of the solution should preferably be above about 6 0 and most preferably be above 6 5 since the solubility of fluorapatite becomes appreciable at a lower p H In 30 addition, the p H of the solution should be below about 11 5 since at higher p H hydroxyapatite having the formula Caj(PQ 4)30 H is preferentially formed rather than fluorapatite A p H below about 9 0 is even more preferred since very little hydroxyapatite is formed at that p H.
When excess available calcium in the form of calcium ion is present, i e in 35 excess of five moles of calcium for each mole of fluoride, even more fluoride is removed as fluorapatite due to the common ion effect of the excess calcium ions and the rate of precipitation is increased In addition, the presence of excess available calcium can reduce the requirement for available phosphate since the excess calcium causes a reduction of initial fluoride by precipitating it as calcium 40 fluoride which does not redissolve rapidly enough to prevent further reduction in fluoride by precipitation as fluorapatite It has, however, been found that when excess calcium is used for initial fluoride reduction, the precipitate should desirably be removed as soon as the concentration of fluoride is sufficiently low to prevent a possible subsequent increase in fluoride by later dissolving of precipitated calcium 45 fluoride When a significant amount of fluoride, i e, about 8 weight percent of the fluoride initially present in the waste water, is precipitated as fluorapatite, the precipitate need not be rapidly removed since the precipitated fluorapatite seems to inhibit the redissolving of precipitated calcium fluoride.
When sufficient excess calcium ion is present and there is sufficient available 50 phosphate to prevent the formation of a permanent calcium fluoride precipitate, i.e, in excess of three moles of available phosphate per mole of fluoride, the fluoride concentration in the waste water can be reduced to below one part per million and even below about 0 1 part per million.
Available calcium in the waste water may be originally present or may be 55 added in the form of a calcium composition which provides available calcium, i e, dissociable calcium compositions Examples of such dissociable calcium compounds include calcium chloride, calcium hydroxide and calcium carbonate.
The calcium hydroxide, Ca(OH)2, can be added to the waste water either in the form of solid calcium hydroxide or in the form of a calcium composition which will 60 form calcium hydroxide upon its addition to the water An example of such a calcium compound which will form calcium hydroxide upon its addition is calcium 4 1,586,545 4 oxide When the waste water is acidic, calcium ions can be provided by the effect of acid upon calcium carbonate which release carbon dioxide and forms a calcium salt The most common source of calcium ions in waste water is generally provided by calcium hydroxide in the form of lime.
As previously discussed, sufficient available phosphate is present in or added 5 to the waste water and is preferably in the amount of at least three moles of available phosphate for each mole of fluoride In general, excess amounts of available phosphate are to be avoided since phosphates are expensive and their discharge into the environment is to be avoided Furthermore, it has been unexpectedly found that excess available phosphate does not substantially further 10 reduce the fluoride over the reduction obtained when only about three moles of available phosphate are present per mole of fluoride to be removed.
The most commonly used and most desirable phosphate composition for providing available phosphate is, phosphoric acid since its addition generally automatically reduces the p H of the waste water to below about 11 5 which is 15 necessary to avoid the formation of hydroxyapatite rather than fluorapatite Other phosphate compositions may however be used when steps are taken to be certain that the p H is held below about 11 5 Such other steps for example include the incorporation of buffers or other acids in the phosphate composition to reduce the p H of the waste water Such buffers or acids may also be added in conjunction with 20 or prior to the incorporation of phosphate in other forms Usually, the addition of zero to five weight percent of phosphoric acid is more than sufficient to provide the correct mole ratio of phosphate ion and to sufficiently reduce p H of the waste water.
Other acids which can be used to reduce p H in addition to or in place of 25 phosphoric acid include inorganic acids such as hydrochloric, nitric, perchloric and sulfuric acids and organic acids such as acetic, tartaric and citric In general, the acid which is selected for p H reduction should provide an ion which will not combine with available calcium to form sufficient calcium compound to reduce the level of available calcium in the waste water below the desirable five moles for each 30 mole of fluoride present in the waste water.
Subsequent to the addition of phosphate and sufficient acid to obtain a solution having a p H below about 11 5, sufficient base, if needed, is added to the solution to obtain a sufficiently high p H to cause the formation of a precipitate.
Insufficient base is added to the solution to raise the p H above about 11 5 since as 35 previously discussed, a p H above about 11 5 will result in the formation of undesirable hydroxyapatite “Base” as used herein is intended to mean any compound or composition which, when added to an aqueous composition, will result in the formation of hydroxy ion The word “acid” as used herein is intended to mean any composition which, when added to an aqueous composition, will cause 40 the formation of hydrogen ion.
Suitable bases for addition to the waste water to raise its p H include any base compound which will not react with calcium and phosphate ions to form a compound which will not convert to fluorapatite Suitable bases include but are not limited to lime, sodium hydroxide, calcium carbonate, sodium carbonate and 45 sodium bicarbonate The most desirable base for large volumes of waste water is lime since it is readily available and provides both a source of calcium ion and is particularly suitable for raising the p H to the appropriate level.
After the precipitate forms, the resulting precipitate is maintained in contact with the water until essentially all fluoride is removed, most of which is desirably 50 chemically combined in water-insoluble fluorapatite often in conjunction with some calcium fluoride The required contact time of the precipitate with the waste water varies greatly between about one second and about one month and is dependent upon seeding, the p H of the waste water and the relative concentrations of available phosphate, available calcium and fluoride These times vary due to 55 different reaction rates and due to intermediate compositions which may form under varying conditions and which require different time periods to convert to fluorapatite For example, when concentration of phosphate and calcium is high and at least some seeding is used, the contact time usually varies from about 1 second to about 10 minutes When concentrations are low and at least some 60 seeding is used, the contact time will usually vary between about two minutes to about two hours When seeding is not used, contact time will usually vary from about thirty minutes to about 24 hours When the p H of the waste water is not in the optimum range, i e, between about 6 5 to about 9 0, longer contact times will be required than when the p H range is within the optimum range 65 1,586,545 5 Fluorapatite is preferentially formed when fluorapite is dispersed in the waste water prior to the formation of a precipitate The dispersed fluorapatite acts as a nucleating agent to cause fluoride to precipitate more rapidly as fluorapatite.
Similarly and unexpectedly calcium fluoride acts as a nucleating agent upon which fluorapatite forms 5 Desirably, only minor amounts of hydroxyapatite form and most desirably the precipitate is essentially free from hydroxyapatite since hydroxyapatite does not contain fluoride and uses up the available calcium and phosphate needed to form fluorapatite After all the fluoride has been removed from the waste water, other precipitates containing calcium and phosphate such as hydroxyapatite may be 10 formed without detrimental effects and such precipitation may in fact be desirable to minimize remaining phosphates in the waste water.
After essentially all fluoride is precipitated from the waste water at least some of which is found in the form of fluorapatite, the precipitate is usually separated from the water and may be treated with acid to form calcium fluoride and water 15 soluble phosphate composition Such acidification is desirably effected at a p H below about 4, preferably below about 3 5 and most preferably below about 3 2.
The acidification p H is generally above about 2 4 since lower p H results in dissolving calcium fluoride by forming soluble HF 2- The optimum acidification p H is between about 2 4 and 3 2 20 The water-soluble phosphate composition obtained from acidifying fluorapatite may be dissolved in aqueous liquid to remove water-insoluble calcium fluoride The dissolved phosphate composition obtained from the fluorapatite may be then continuously recycled to additional waste water containing fluoride to provide at least a portion and desirably most of the required available phosphate 25 Furthermore, water-soluble calcium composition may be but is not necessarily simultaneously formed upon acidification of the fluorapatite and may be simultaneously dissolved with the phosphate composition in an aqueous liquid to remove it from water-insoluble calcium fluoride and continuously recycled with the water-soluble phosphate composition to additional waste water containing 30 fluoride to provide at least a portion of the required available calcium.
For example, when fluorapatite is treated with sulfuric acid watersoluble phosphoric acid and water-insoluble calcium sulfate are obtained and when fluorapatite is treated with hydrochloric acid water-soluble phosphoric acid and water-soluble, calcium chloride are obtained Nitric and perchloric are also 35 suitable acids.
All of the precipitated fluorapatite need not be treated with acid and a portion of the untreated fluorapatite can be dispersed in the additional waste water prior to the formation of further precipitate Such dispersion is advantageous since the fluorapatite acts as a nucleating agent to cause fluoride to precipitate more rapidly 40 as fluorapatite It is further believed that the dispersed fluorapatite causes direct precipitation of fluorapatite thus avoiding intermediate compositions which subsequently convert to fluorapatite Similarly, a portion of precipitated calcium fluoride can be recycled as a nucleating agent alone or combined with the fluorapatite 45 Although it is not essential, the use of excessive phosphate composition in the process of the invention can be avoided by pretreating waste water containing an excess of about 8 parts per million of fluoride ion with calcium ion to precipitate the excess fluoride ion as calcium fluoride The pretreated waste water is then further treated with calcium ion and phosphate ion in accordance with the process 50 of the invention It has been unexpectedly found that precipitated calcium fluoride need not be removed prior to treatment with phosphate and calcium to remove remaining fluoride as fluorapatite and in fact, it has been unexpectedly found that the presence of the calcium fluoride accelerates precipitation of fluorapatite After precipitation of remaining fluoride as fluorapatite, when calcium fluoride is 55 present, the precipitate should be removed to prevent subsequent increase in fluoride which sometimes results from redissolving of calcium fluoride.
The process of the invention can be made a continuous process for purifying water containing fluoride As a first step in one embodiment of continuous process sufficient calcium composition is continuously added to a stream of the waste water 60 to provide at least five moles of available calcium in the waste water for each mole of fluoride in the waste water.
Sufficient phosphate composition to obtain at least three moles of available phosphate for each mole of fluoride is then continously added to the stream The phosphate composition is desirably selected to provide a p H in the waste water of 65 6 1,586,545 6 from about 6 0 to about 11 5 after its addition and more desirably from about 6 5 to about 90 after its addition If the phosphate composition is not so selected, sufficien acid or base is added in conjunction with the phosphate composition to provide waste water within the about 6 0 to about 11 5 range and more desirably within /he about 6 5 to about 9 0 p H range 5 As the precipitation reaction proceeds, the p H drops and may drop to a level which results in undesirably high solubility of the precipitate After precipitation the most desirable end p H is between about 6 5 to about 9 which if necessary is obtained by at least one upward p H adjustment with base.
Essentially simultaneously with the addition of phosphate composition, a 10 compound selected from fluorapatite, calcium fluoride and mixtures thereof is slurried into the waste water stream as a nucleating agent The nucleating agent is most preferably fluorapatite A precipitate is then permitted to form which contains essentially all fluoride present in the waste water The fluoridecontaining precipitate is then separated from the waste water and at least a portion of the 15 precipitate is acidified and the resulting phosphate containing liquid is recycled as at least a portion of the phosphate composition.
A portion of the calcium ion which is added to the waste water stream is desirably added by dissolving lime in the waste water stream In addition, at least a portion of the calcium ion may be added as a water-soluble calcium salt in 20 conjunction with or prior to the addition of the phosphate composition Such water soluble calcium salt can be obtained by recycling water-soluble calcium composition which is obtained at the time that the precipitate is acidified The precipitate may be acidified with any suitable acid which will form watersoluble phosphate and calcium compounds The most desirable acids for such acidification 25 are hydrochloric acid and sulfuric acid.
The precipitate which forms in a waste water stream as a result of either the continuous or batch process of the invention may be removed by passing the waste water through a settling tank having sufficient residence time to permit the precipitate to be removed from the waste water by settling or alternatively the 30 waste water may be passed through a filter or centrifuge to remove the precipitate.
Fluorapatite or calcium fluoride which is slurried into the waste water as a nucleating agent may be obtained by slurrying a portion of the precipitate which forms as a result of the process since the precipitate contains fluorapatite and usually some calcium fluoride 35 Calcium fluoride which is slurried into the waste water as nucleating agent may be obtained as a portion of the precipitate which forms from the process when the waste water contains more than about eight parts per million of fluoride and sufficient calcium composition is added to exceed the solubility limits of calcium fluoride 40 As indicated previously, the process of the invention may be operated continuously Thus one embodiment of continous process according to the invention for purifying a stream of water containing fluoride and sufficient calcium composition to provide at least five moles of available calcium in the water for each mole of fluoride in the water comprises: 45 (a) continuously adding sufficient phosphate composition to said stream, said phosphate composition being selected to provide a p H in the water of below 11 5 after its addition; (b) adjusting the p H of the water to above 6 0 with a base; (c) slurrying a seeding composition selected from fluorapatite, calcium 50 fluoride and mixtures thereof into said stream; and (d) permitting a precipitate to form which contains essentially all fluoride which was present in the water An alternative procedure comprises the steps of:
(a) continuously adding phosphate composition to a stream of said water to provide sufficient available phosphate in said water; 55 (b) adding from 0 to about 5 weight percent acid to said water to obtain a water p H of from about 6 0 to 11 5; (c) substantially simultaneously with obtaining said p H of from about 6 0 to about 11 5 slurrying a seeding composition into said stream, said seeding compositing being selected from fluorapatite, calcium fluoride and mixtures 60 thereof; and (d) permitting a precipitate to form which contains essentially all fluoride which was present in the water.
In the following Examples, Examples 27 to 59 serve to illustrate the process of the invention and are not to be considered a limitation thereof Examples I to 26 65 are for purposes of comparison All parts and percentages in the following examples are by weight.
EXAMPLE 1 ml of a 0 0526 molar calcium acetate solution, 30 ml of a 0526 molar phosphoric acid solution and 10 ml of a 0 0526 sodium fluoride solution are mixed 5 and sufficient water is immediately added to raise the volume to 100 ml which results in a 0 00526 molar ( 100 parts per million) fluoride solution having a molar ratio of calcium to phosphate to fluoride of 5 5 to 3 to 1 The p H is then adjusted to between 7 5 and 8 with 0 2 molar sodium hydroxide and allowed to stand for about2 hours The solution is then filtered to remove the precipitate The filtrate is tested 10 for fluoride concentration by means of a fluoride ion specific electrode and found to contain 0 2 parts per million (ppm) fluoride.
This example clearly illustrates the superior removal of fluoride from the water in accordance with the process of the invention.
EXAMPLES 2 to 5 15 The procedure of Example 1 is followed except varying volumes of the calcium acetate and phosphoric acid solutions are added to vary the molar ratio.
TABLE I
Molar ratio Ca’+ to Final fluoride PO: to F concentration in ppm 20 2 ito Otol 9 6 ppm F3 2 5 to I to 1 8 3 ppm F4 3 2 to I to 1 1 5 ppm F5 5 to 0 6 to 1 5 0 ppm FWhen compared with Example 1 these examples show that the most desirable 25 molar ratio of calcium to phosphate to fluoride is 5 to 3 to 1 and further show that a satisfactory result can be obtained when there is a molar ratio of about 3 to 1 to 1 and that calcium and phosphate concentrations should desirably not be dropped below those levels.
EXAMPLE 6 30
Sufficient calcium and phosphate is added to a 0 00032 molar ( 6 2 ppm) fluoride solution to obtain a 0 0158 molar calcium ion concentration and a 0 00790 phosphate ion concentration This solution represents a molar ratio of calcium to phosphate to fluoride of about 48 to 24 to 1 The resulting solution adjusted to a p H of between 8 1 and 8 6 with 0 2 M Na OH and is allowed to stand for 20 hours and is 35 filtered to remove precipitate The filtrate is analyzed for fluoride concentration with a fluoride ion specific electrode and is found to contain 0 008 parts per million fluoride.
This example demonstrates that when an appropriate substantial excess over five moles of calcium per mole of fluoride and an appropriate substantial excess 40 over three moles of phosphate per mole of fluoride is incorporated into a solution containing fluoride, a precipitate will form which can reduce fluoride concentration in the solution to below 0 01 parts per million.
EXAMPLE 7
The procedure of Example 6 is followed except the molar calcium ion 45 concentration is 0 00526 and the molar phosphate ion concentration is 0 00158 which represents a molar ratio of calcium to phosphate to fluoride of 16 to 5 to 1.
The filtrate is found to have a fluoride ion concentration of 0 056 ppm which demonstrates a slight increase in residual fluoride apatite ratio of 5 to 3 to 1 but which still results in a fluoride concentration of less than 0 1 parts per million 50 EXAMPLE 8
The procedure of Example 6 is followed except that the initial fluoride concentration is 0 000737 molar ( 14 ppm), the calcium concentration is 0 0153 molar and the phosphate concentration is 0 00316 which represents a molar ratio of calcium to phosphate to fluoride of 20 to 4 2 to 1, the p H is adjustedto 7 and the 55 solution is filtered after 24 hours The filtrate is found to contain 0 46 ppm fluoride.
EXAMPLE 9
The procedure of Example 8 is followed except that the molar ratio is 17 to 2 to 1,586,545 I of calcium to phosphate to fluoride The filtrate is found to contain 2 2 ppm fluoride This example illustrates that as the molar ratio of phosphate to fluoride becomes lower than 3 to 1, a residual fluoride concentration can be obtained which is still below three parts per million but that there is a significant increase in residual fluoride when compared with the situation where the molar ratio of 5 phosphate to fluoride is higher than 3 to 1.
EXAMPLE 10
The procedure of Example 6 is followed except the molar concentration of calcium is 0 0184 and the molar concentration of phosphate is 0 00947 representing a molar ratio of calcium to phosphate to fluoride of 56 to 28 to 1 The filtrate is 10 found to contain 0 018 ppm fluoride.
EXAMPLE 11
A solution is prepared containing a 0 0153 molar concentration of calcium, a 0.00316 molar concentration of phosphate and a 0 000274 molar ( 5 2 ppm) concentration of fluoride at a p H below 6 15 The p H is then adjusted to 6 with 02 M Na OH No precipitate forms after a period of eight hours when no seeding is used.
EXAMPLES 12 to 20 The procedure of Example 11 is followed except the p H is adjusted to various higher levels which cause the formation of a precipitate and the fluoride 20 concentration is measured after about 8 hours The results are in Table II below.
TABLE II
Example p H ppm F found 12 6 50 0 04 13 7 00 0 02 25 14 7 50 0 05 8 10 0 07 16 8 60 3 4 17 9 10 3 2 18 9 60 3 2 30 19 10 20 3 2 10 60 4 8 This example shows that over a period of about eight hours when no seeding is used, the most desirable p H range is between about 6 5 and about 8 5.
EXAMPLE 21 35
A solution is prepared at a p H below 6, containing a 0 000737 molar ( 14 ppm) fluoride concentration, a 0 00316 molar phosphate concentration and a 0 00626 calcium concentration The p H is then adjusted to 6 6 with 0 2 M Na OH The fluoride concentration of the filtrate is measured after the expiration of 5 hours and is found to contain 3 6 parts per million fluoride and after 35 hours is found to 40 contain 0 46 ppm fluoride.
EXAMPLE 22 to 26 The procedures of Example 21 is followed except the p H is adjusted to various levels The results are set forth in Table III below:
TABLE III 45
Example p H F after 5 hours F after 35 hours 22 6 00 No precipitate No precipitate 23 7 00 1 2 ppm 0 1 ppm 24 7 5 1 2 ppm 0 6 ppm 25 8 0 1 5 ppm 0 3 ppm 50 26 8 6 1 8 ppm 0 3 ppm Examples 21 to 26 show that waiting a longer period for completion of fluoride removal results in lower residual fluoride with the p H range 6 6 to 8 6.
EXAMPLE 27
A solution is prepared which contains a 0 000368 molar ( 7 ppm) fluoride ion 55 1,586,545 9 1S 4 O concentration, a 0 00204 molar phosphate ion concentration and a 0 0134 molar calcium ion concentration The p H is then immediately adjusted to 6 25 and 0.000737 millimoles of solid fluorapatite is immediately slurried into the solution.
The solution is then immediately filtered and the filtrate is measured for fluoride ion The results are in Table IV.
EXAMPLES 28 to 53 The procedure of Example 27 is followed except the initial p H and the elapsed time before filtering are varied The p H is adjusted upwardly to within about one p H point above the initial p H with 0 2 M Na OH when the p H drops to from about 5 to 6 due tothe precipitationreacffon The p H is not adjusted upwardly until the p H drops to the range of from about 5 to 6 since the reaction continues down to p H 5 to 6 A p H adjustment is indicated in the Table by an asterisk.
Example
27 28 29 30 31 32 33 34 35 36 37 38 39 40 Time in minutes between slurrying and filtering immediate 1 3 6 8 immediate 1 7 4446 47 48 49 51 52 53 54 56 57 TABLE IV double seed added double seed added double seed added double seed added double seed added 1 3 9 2 207 327 2 353 493 Initial p H 6.25 6.25 6.25 6.25 6.25 6.25 6.80 6.80 6.80 6.80 6.80 6.80 6.80 6.80 6.80 6.80 6.80 6.80 7.00 7.00 7.00 7.00 7.00 7.00 8.10 8.10 8.10 8.10 8.60 8.60 8.60 8.60 ppm F2.2 1.0 0.9 0.26 0.05 0.01 1.5 0.8 0.5 0.4 0.1 0.05 0.05 0.5 0.3 0.2 0.1 0.03 4.6 2.6 1.2 0.7 0.07 0.02 4.6 3.2 1.0 0.18 4.6 4.3 1.2 0.4 Examples 27 to 58 show that seeding with fluorapatite greatly increases the rate at which fluoride is removed from solution particularly at an initial p H range of from 6 25 to 7 00 A comparison of Examples 40 to 44 shows that increased seeding even further increases the rate of fluoride removal These examples also show that the p H of the solution drops as fluoride is removed from solution in a precipitate.
EXAMPLE 59
A solution containing a 0 000545 molar ( 10 ppm) fluoride ion concentration, a 0.00647 molar calcium ion concentration and a 0 00316 molar phosphate ion 1.586 545 ao concentration, is allowed to stand for several days at a p H of 6 6 without forming a precipitate 0 000247 moles of calcium fluoride are then slurried into the solution and after thirteen minutes the fluoride ion concentration is found to be reduced from 10 ppm to 5 6 ppm The p H is then raised to about 7 and after only 2 5 more minutes, the fluoride ion concentration is found to be 2 2 ppm 5 This example illustrates that calcium fluoride acts to accelerate the removal of fluoride as precipitated fluorapatite and does not seem to substantially interfere with fluoride removal.

Claims (1)

WHAT WE CLAIM IS:-
1 A process for purifying water containing fluoride which comprises adjusting 10 the composition of the water by providing sufficient available calcium and sufficient available phosphate to enable at least a portion of said fluoride to be precipitated as fluorapatite and if necessary adjusting the p H and in which a seeding composition selected from fluorapatite, calcium fluoride and mixtures thereof is dispersed into said waste water to act as a nucleating agent whereby a 15 precipitate is formed containing essentially all fluoride initially present in the water.
2 A process according to Claim 1 wherein sufficient phosphate composition is added to provide at least three moles of available phosphate for each mole of fluoride 20 3 A process according to Claim 1 or Claim 2 wherein said available calcium is calcium ion, said available phosphate is phosphate ion, and said fluoride is fluoride ion.
4 A process according to any one of Claims 1 to 3 wherein the fluoride containing precipitate is separated from the water 25 A process according to Claim 4 wherein said water is passed through a settling tank having sufficient residence time to permit said precipitate to be removed from the water by settling.
6 A process according to Claim 4 wherein said water is passed through a filter to remove said precipitate 30 7 A process according to Claim 4 wherein said precipitate is removed by a centrifuge.
8 A process according to Claim 4 wherein a portion of the precipitate is recycled to the process as seeding composition.
9 A process according to any preceding claim wherein said seeding 35 composition comprises fluorapatite.
A process according to any one of Claims 4 to 9 wherein at least a portion of the fluoride containing precipitate is acidified and the resulting phosphatecontaining liquid is recycled as at least a portion of said phosphate composition.
11 A process according to Claim 10 wherein said acidification provides at 40 least some water-soluble calcium composition which is recycled with the phosphate composition.
12 A process according to Claim 10 or Claim 11 wherein said precipitate is acidified with hydrochloric acid.
13 A process according to any one of Claims 1 to 12 wherein at least a portion 45 of said available calcium is added by dissolving lime in the water.
14 A process according to any one of Claims I to 13 wherein at least a portion of the calcium is added as a water-soluble calcium salt in conjunction with the addition of the phosphate composition.
15 A continuous process according to any one of Claims I to 14 for purifying a 50 stream of water containing fluoride and sufficient calcium composition to provide at least five moles of available calcium in the water for each mole of fluoride in the water which comprises:(a) continuously adding sufficient phosphate composition to said stream, said phosphate composition being selected to provide a p H in the water of below 11 5 55 after its addition; (b) adjusting the p H of the water to above 6 0 with a base; (c) slurrying a seeding composition selected from fluorapatite, calcium fluoride and mixtures thereof into said stream; and (d) permitting a precipitate to form which contains essentially all fluoride 60 which was present in the water.
16 A process according to Claim 15 wherein calcium composition is provided by continuously adding sufficient calcium composition to said stream to provide lo 1.586-545 l o the at least five moles of available calcium in the water for each mole of fluoride in the water.
17 A continuous process according to any one of Claims 1 to 14 which comprises the steps of:
(a) continuously adding sufficient calcium composition to a stream of water to 5 provide at least five moles of available calcium in said water for each mole of fluoride in said water; (b) continuously adding sufficient phosphate composition to said stream, said phosphate composition being selected to provide a p H in the water of from 6 0 to about 11 5 after its addition; 10 (c) substantially simultaneously with the addition of said phosphate composition slurrying a seeding composition selected from fluorapatite, calcium fluoride and mixtures thereof into said stream; and (d) permitting a precipitate to form which contains essentially all fluoride which was present in the water 15 18 A continuous process according to any one of Claims I to 14 for purifying water containing fluoride and at least five moles of available calcium for each mole of fluoride which comprises the steps of:
(a) continuously adding phosphate composition to a stream of said water to provide sufficient available phosphate in said water; 20 (b) adding from 0 to about 5 weight percent acid to said water to obtain a water p H of from about 6 0 to 11 5; (c) substantially simultaneously with obtaining said p H of from about 6 0 to about 11 5 slurrying a seeding composition into said stream, said seeding composition being selected from fluorapatite, calcium fluoride and mixtures 25 thereof; and (d) permitting a precipitate to form which contains essentially all fluoride which was present in the water.
19 A process according to Claim 18 wherein the p H obtained in step (b) is from about 6 5 to about 9 0 30 A process according to any one of Claims 1 to 19 wherein the end p H after precipitation is between about 6 5 and about 9 0.
21 A process according to Claim 20 wherein at least one upward p H adjustment is made with base to obtain said end p H.
22 A process according to any one of Claims 1 to 21 wherein the acid used to 35 obtain a p H of from about 6 0 to about 11 5 and phosphate composition added to provide sufficient available phosphate are the same and are phosphoric acid.
23 A process according to Claim I for purifying water containing fluoride by providing sufficient available calcium and sufficient available phosphate to precipitate at least a portion of said fluoride as fluorapatite, and in which said 40 fluorapatite is separated from said water and treated with acid to form calcium fluoride and water soluble phosphate composition and said water-soluble phosphate composition is continuously recycled as phosphate to additional water containing fluoride.
24 A process according to Claim 25 wherein water-soluble calcium 45 composition is also formed upon acidification and is recycled with the phosphate composition.
A process according to Claim 23 or Claim 24 wherein said treating acid is selected from nitric, hydrochloric, perchloric and sulfuric acid.
26 A process as claimed in Claim I substantially as hereinbefore described 50 with particular reference to Examples.
MATHYS & SQUIRE Chartered Patent Agents Fleet Street London EC 4 Y l AY Agents for the Applicants Printed for Her Majesty’s Stationery Office, by the Courier Press, Leamington Spa, 1981 Published by The Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.
1 1 I 1,586,545 1 1

GB2864/78A
1977-01-24
1978-01-24
Process for purifying water containing fluoride ion

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Process for purifying waste water containing fluoride ion

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Families Citing this family (30)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

NL187312C
(en)

1978-05-18
1991-08-16
Dhv Raadgevend Ing

METHOD FOR DEPOSPHATING WATER.

US4226710A
(en)

1979-02-12
1980-10-07
Andco Industries, Inc.
Process for purifying water containing fluoride ion

US4323462A
(en)

1979-02-12
1982-04-06
Andco Industries, Inc.
Process for purifying water containing fluoride ion

NL7905111A
(en)

1979-06-30
1981-01-05
Stamicarbon

METHOD FOR CHEMICAL REMOVAL OF PHOSPHORUS COMPOUNDS FROM WASTE WATER AND METHOD FOR PURIFYING WASTE WATER.

DE3307315A1
(en)

1983-03-02
1984-09-06
Krupp-Koppers Gmbh, 4300 Essen

METHOD FOR CLEANING CHEMICAL GIPS

US5215632A
(en)

1990-04-30
1993-06-01
Occidental Chemical Corporation
Fluoride removal from aqueous streams

US5158686A
(en)

1991-02-25
1992-10-27
Envar Services, Inc.
Impurity removal process and apparatus

FR2676727B1
(en)

1991-05-24
1994-04-15
Hydro Azote

PROCESS FOR THE TREATMENT AND RECYCLING OF WASTE WATER LOADED WITH FLUORINE.

US5403495A
(en)

1992-03-13
1995-04-04
Tetra Technologies, Inc.
Fluoride removal system

US6428705B1
(en)

1996-11-26
2002-08-06
Microbar Incorporated
Process and apparatus for high flow and low pressure impurity removal

US6613230B2
(en)

2000-07-07
2003-09-02
Ionics, Incorporated
Method for simultaneous removal of arsenic and fluoride from aqueous solutions

US6863825B2
(en)

2003-01-29
2005-03-08
Union Oil Company Of California
Process for removing arsenic from aqueous streams

US20100187178A1
(en)

2003-01-29
2010-07-29
Molycorp Minerals, Llc
Process for removing and sequestering contaminants from aqueous streams

US8066874B2
(en)

2006-12-28
2011-11-29
Molycorp Minerals, Llc
Apparatus for treating a flow of an aqueous solution containing arsenic

US8349764B2
(en)

2007-10-31
2013-01-08
Molycorp Minerals, Llc
Composition for treating a fluid

US8252087B2
(en)

2007-10-31
2012-08-28
Molycorp Minerals, Llc
Process and apparatus for treating a gas containing a contaminant

US20090107919A1
(en)

2007-10-31
2009-04-30
Chevron U.S.A. Inc.
Apparatus and process for treating an aqueous solution containing chemical contaminants

US20090107925A1
(en)

2007-10-31
2009-04-30
Chevron U.S.A. Inc.
Apparatus and process for treating an aqueous solution containing biological contaminants

US20100155330A1
(en)

2008-11-11
2010-06-24
Molycorp Minerals, Llc
Target material removal using rare earth metals

TW201038510A
(en)

2009-03-16
2010-11-01
Molycorp Minerals Llc
Porous and durable ceramic filter monolith coated with a rare earth for removing contaminates from water

AR076275A1
(en)

2009-04-09
2011-06-01
Molycorp Minerals Llc

USE OF A RARE LAND FOR THE REMOVAL OF ANTIMONY AND BISMUTE

JP2012532201A
(en)

2009-07-06
2012-12-13
モリーコープミネラルズエルエルシー

Method for forming rare earth-containing particles

MX2012005351A
(en)

2009-11-09
2012-11-23
Molycorp Minerals Llc
Rare earth removal of colorants.

US9539445B2
(en)

2010-11-22
2017-01-10
Taipei Medical University
Type of anion-containing calcium phosphate compound for dental remineralization

US9233863B2
(en)

2011-04-13
2016-01-12
Molycorp Minerals, Llc
Rare earth removal of hydrated and hydroxyl species

WO2014094147A1
(en)

2012-12-17
2014-06-26
Chemetics Inc.
Improved method for removing fluoride from aqueous streams

WO2015134981A2
(en)

2014-03-07
2015-09-11
Molycorp Minerals, Llc
Cerium (iv) oxide with exceptional arsenic removal properties

CN106669550B
(en)

2016-11-30
2022-07-01
江苏永冠给排水设备有限公司
High-speed reaction kettle equipment for defluorination water treatment based on planting method and use method thereof

CN112811646B
(en)

2020-12-24
2022-09-06
山东华氟化工有限责任公司
Method for treating wastewater with high fluorine ions, high COD (chemical oxygen demand) and high chroma

CN113213518A
(en)

2021-05-20
2021-08-06
安徽舜禹水务股份有限公司
High ammonia nitrogen high alkalinity waste water resource system

Family Cites Families (6)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

US2380800A
(en)

1939-05-20
1945-07-31
Howard V Smith
Water treatment

US3284350A
(en)

1964-02-12
1966-11-08
Nat Steel Corp
Removal of tin and fluoride from aqueous solutions of the same

US3467496A
(en)

1966-11-07
1969-09-16
American Cyanamid Co
Process for preparing wet process phosphoric acid and calcium sulfate from phosphate rock

US3552918A
(en)

1966-11-08
1971-01-05
Dorr Oliver Inc
Process for the production of phosphoric acid

US3551332A
(en)

1969-06-16
1970-12-29
Int Minerals & Chem Corp
Purification of fluorine-containing industrial waste waters

JPS5199853A
(en)

1975-02-28
1976-09-03
Hitachi Ltd

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1977-01-24
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US05/761,685
patent/US4145282A/en
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1978

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1978-07-24

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1978-08-18

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1979-08-02

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1980-07-22

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1978-07-25

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1978-09-21

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