US2767136A - Process of eliminating arsenic compounds from phosphoric acid - Google Patents
Process of eliminating arsenic compounds from phosphoric acid Download PDFInfo
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- US2767136A US2767136A US453295A US45329554A US2767136A US 2767136 A US2767136 A US 2767136A US 453295 A US453295 A US 453295A US 45329554 A US45329554 A US 45329554A US 2767136 A US2767136 A US 2767136A
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- acid
- phosphoric acid
- arsenic
- copper
- iodine
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/18—Phosphoric acid
- C01B25/234—Purification; Stabilisation; Concentration
- C01B25/237—Selective elimination of impurities
- C01B25/238—Cationic impurities, e.g. arsenic compounds
Definitions
- the present invention relates to a process of eliminating arsenic compounds from phosphoric acid by electrolysis.
- phosphoric acids with a content of about 20 percent to about 95 percent of H3PO4, preferably with a content ranging between 50 percent and 90 percent of H3PO4.
- the time required for the electro-deposition of arsenic from phosphoric acid containing arsenic compounds is extraordinarily long as compared, under otherwise the same conditions, with the electro-deposition of other metals having the same place in the electrochemical series. It is known to use copper as cathode and platinum as anode and a cathodic current density of not more than 1 ampere per square decimetre or to accelerate the electro-deposition of arsenic from phosphoric acid by the simultaneous electrodeposition of copped. When using this method of working a ratio of the contents of copper and arsenic in the acid of l to at least 2, or better still of 1:25 to 1:4, is advantageously used.
- the present invention is based on the observation that arsenic compounds are deposited by electrolysis from phosphoric acid by operating with addition of copper compounds and by depositing the arsenic compounds by the action of iodine during the electrolysis in the form of arsenic. It was found that small amounts of iodine, i. e. a few milligrams per kilogram of acid, increase the speed of deposition of arsenic from phosphoric acid in an extraordinary and sudden manner.
- the desired iodine content can be attained by adding an aqueous iodine solution to the phosphoric acid or by working in such a way that iodine is formed from iodides during the reaction.
- iodides there come into consideration, in addition to CuI, all soluble iodides such as Nal, Kl, NHI, Cal-z, Balz, SrI2, Mglz. Hydriodic acid may also be used.
- copper compounds are suitable all soluble copper salts either as such or in solution, the anionic component of which does not have a disturbing effect regarding the purity of the phosphoric acid.
- the anionic component of which does not have a disturbing effect regarding the purity of the phosphoric acid There are mentioned, for instance, CuCl2, CuSO4, Cu(NO3)z, CuBrz, Cu-acetate.
- iodine should advantageously be kept in its limits since otherwisethe elimination of arsenic is deteriorated as is shown by. the following table but Addition to phosphoric Content of acid arsenic in the phosphoric Cu ions, Iodine, acid, mgsJkg. of mgsJkg. mgsJkg.
- Figure 1 represents a side elevation of the apparatus
- Figure 2 represents a top view.
- the electric current required for the electrolysis is supplied over the anode 7 having a cylindrical shape and consisting of a platinum wire gauze and over the cathode 8 being likewise of a cylindrical shape and consisting of a copper wire gauze.
- the stirrer 6 efiects the thorough mixing of the reaction mixture.
- the phosphoric acid which is now free from arsenic leaves the electrolytic vessel 3 through the outlet 5.
- Supply and discharge of the phosphoric aye-arse acid are regulated in such away that the acid is subjected to electrolysis tor about 30 minutes.
- the process may also be carried out discontinuously.
- the following examples serve to illustrate the inventio but they'are' notintended to limit it' theretoi Emmnle 1 3 litres of phosphoric acid (8.085, percent), which contain 40 milligrams of arsensic per kilogram of acid in the form of arsenic compounds, are heatedto 9.0? C. and stirred by means of, a stirrer (3-5 revolutions per second).
- Into this phosphoric acid are placed as cathode two copper wire gauzes of cylindrical shape which are inserted into each other, and have a height of 13 cuts. 2 -2 d ameter ofi 4 and. BI cms. respectively. Between the ZIcopper wire gauzesai platinum.
- wire-gauze electrode is placed as. anode. '40. milligrams of copper ions per kilogram of acid in the form of an aqueous copper sulfate. sohltion-as concentrated as possible and 1.8 milligrams of iodine per kilogram. of acid injthe form of an aqueous 0.1 N-solution of iodine 'are'added and. the acid is electrolyzed under 3. volts. and at 5 'amperes.” After about 30. minutes the acid'is free from arsenic.'
- the afrangement ofthe electrodes is thesame as described 1 40 milligrams of copperpe'r kilogranioff-acid e form of! dry. copper phosphate and"l.'8' milligrams of iodine per kilogram of-acid in 'the form of an aqueous 0L1" N- iodine: solution are then added and the acidis eleotrolyzed :as. described in Example 1. 'A phbsphorlc acid which is "free from: arsenic is obtained; i
- P QI o l mina i arse i ompoun from phosphoric acid by electrolysis in which .the electrolysis is'oarried out with a phosphoric acid which, at the commenee'ment r the deposition, contains arsenic. and copper' in a proportion by weight ranging from between about lziabout 0.2 to about l:about 5,' and copper and iodine in a proportion by. weight ranging. from between about 4010,6to 40 23.0.
- A'procss. of eliminating arsenic compounds from phosphoric acid. by electrolysis in which the electrolysis is. carried out with a phosphoric acid which, at the commencement of the deposition, contains arsenic and copper in'a proportion by weight ranging from between about l z-about 0.2 to about lzabout 5, and in which an iodine solution is. added to-the phosphoric acid insuch a quantity. that the proportion by weight of copper to iodine ranges from. between about 40:06 to 40:30.
- a process ofeliminating-arsenic compounds from phosphoric acid by electrolysis in which the electrolysis I iscarried' out with a phosphoric acid which, at the com-' mencement of the deposition, contains arsenic and copper in a proportion by weightranging from between about l:'about0.2'to about lfabout 5 and in which the desired iodine content is attained by 'the formation of iodine "front iodides during the reaction, these iodides being added to the phosphoric :acid in such a quantity that copper and iodine are present in a proportion by weight ran'ging from betweenabout 40-:0.-6 to 40:3.0.
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- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Electrolytic Production Of Metals (AREA)
Description
Oct. 16, 1956 oms ETAL 2,767,136
PROCESS 0. ELIMINATING ARSENIC COMPOUNDS FROM PHOSPHORIC ACID- Filed Aug. 31, 1954 Franz Rod/s He/mut Klee INVENTORS m ATTORN Y:
United States PatentO "ice PROCESS OF ELllVHNATlNG ARSENIC COM- POUNDS FROM PHOSPHORIC ACID Franz Rodis and Helmut Klee, Knapsaclr, near Koln,
Germany, assignors to Knapsack-Griesheim Aktiengesellschaft, Knapsack-Bezirk Koln, Germany, a company of Germany Application August 31, 1954, Serial No. 453,295-
Claims priority, application Germany September 2, 1953 Claims. (Cl. 204130) The present invention relates to a process of eliminating arsenic compounds from phosphoric acid by electrolysis. For this process there come into consideration phosphoric acids with a content of about 20 percent to about 95 percent of H3PO4, preferably with a content ranging between 50 percent and 90 percent of H3PO4.
The time required for the electro-deposition of arsenic from phosphoric acid containing arsenic compounds is extraordinarily long as compared, under otherwise the same conditions, with the electro-deposition of other metals having the same place in the electrochemical series. It is known to use copper as cathode and platinum as anode and a cathodic current density of not more than 1 ampere per square decimetre or to accelerate the electro-deposition of arsenic from phosphoric acid by the simultaneous electrodeposition of copped. When using this method of working a ratio of the contents of copper and arsenic in the acid of l to at least 2, or better still of 1:25 to 1:4, is advantageously used. Examinations showed, however, that the arsenic concentrations in the phosphoric acid, under otherwise the same conditions, continuously decrease with increasing additions of copper ions. Satisfactory results are only obtained if about 5 to about times as many copper ions as arsenic are present in the acid.
The present invention is based on the observation that arsenic compounds are deposited by electrolysis from phosphoric acid by operating with addition of copper compounds and by depositing the arsenic compounds by the action of iodine during the electrolysis in the form of arsenic. It was found that small amounts of iodine, i. e. a few milligrams per kilogram of acid, increase the speed of deposition of arsenic from phosphoric acid in an extraordinary and sudden manner. It is of advantage to operate at the commencement of the deposition with a proportion by weight of arsenic to copper in the phosphoric acid ranging from about lzabout 0.2 to about lzabout 5 as well as with a proportion by weight of copper to iodine ranging from about l00:about 0.5 to about 100zabout 50. It has proved of special advantage to maintain the proportion by weight of copper to iodine at a value ranging between 100:2 and 100215. The operation is advantageously carried out while stirring and at temperatures ranging between about 60 C. and about 250 C., preferably between 60 C. and about 150 C.
The desired iodine content can be attained by adding an aqueous iodine solution to the phosphoric acid or by working in such a way that iodine is formed from iodides during the reaction. As iodides there come into consideration, in addition to CuI, all soluble iodides such as Nal, Kl, NHI, Cal-z, Balz, SrI2, Mglz. Hydriodic acid may also be used.
As copper compounds are suitable all soluble copper salts either as such or in solution, the anionic component of which does not have a disturbing effect regarding the purity of the phosphoric acid. There are mentioned, for instance, CuCl2, CuSO4, Cu(NO3)z, CuBrz, Cu-acetate.
2,767,136 Patented Oct. 16, 1956 t 2 The use of Cu-phosphate is of special advantage CuI may also be used as was already mentioned.
The examples given further below show that a phosphoric acid which is practically free from arsenic is obtained when working with an arsenic concentration of 40 milligrams per kilogram of acid and with an iodine concentration of about 1.8 milligrams per kilogram of acid. The copper ions are deposited on the cathode and are no longer detectable in the phosphoric acid after the electrolysis.
When copper ions are added in the form of copper sulfate, merely the sulfate anion of the copper sulphate remains in the phosphoric acid. If one wants to avoid this, copper phosphate must be added straight away or the necessary quantity of copper must be dissolved in the required quantity of phosphoric acid at the anode.
The addition of iodine should advantageously be kept in its limits since otherwisethe elimination of arsenic is deteriorated as is shown by. the following table but Addition to phosphoric Content of acid arsenic in the phosphoric Cu ions, Iodine, acid, mgsJkg. of mgsJkg. mgsJkg.
acid of acid of acid untreated phosphoric 40 7 acid 40 0. 6 3 40 1. 2 1 40 1. 8 0 40 3.0 6
From the above table can be seen that, when reducing the addition of iodine from 1.8 to 0.6 milligrams per kilogram of acid, the content of arsenic rises again from practically zero to 3 milligrams per kilogram of acid. When raising the addition of iodine from 1.8 to 3 milligrams per kilogram of acid the content of arsenic in the phosphoric acid rises likewise from practically zero to 5milligrams per kilogram of acid.
An increase of the copper ions is likewise detrimental. Using a content of 1.8 milligrams of iodine per. kilogram of acid and increasing the additions of copper ions from 40 to 68 and then to 112 milligrams, the arsenic content rises from practically zero to 3 milligrams per kilogram of phosphoric acid.
The process according to the present invention is illustrated in'the accompanying diagrammatic drawings. Figure 1 represents a side elevation of the apparatus, Figure 2 represents a top view.
140 milligrams of copper ions per kilogram of acid in the form of a very concentrated solution of copper salt and l.8,millig1ams' of iodine per kilogram of acid-in the form of an aqueous 0.1N-solution of iodine are added to the phosphoric acid which contains arsenic. The whole is passed through the tube 4 into a double-walled vessel 3 which has an acid-proof brick lining and which is provided with a supply pipe 1 and a drain pipe 2 for the heating liquid and is then heated to about C. by means of the heating liquid. The electric current required for the electrolysis is supplied over the anode 7 having a cylindrical shape and consisting of a platinum wire gauze and over the cathode 8 being likewise of a cylindrical shape and consisting of a copper wire gauze. The stirrer 6 efiects the thorough mixing of the reaction mixture. On termination of the electrolysis which takes place under a tension of about 3 volts and at an amperage of about 5 amperes, the phosphoric acid which is now free from arsenic leaves the electrolytic vessel 3 through the outlet 5. Supply and discharge of the phosphoric aye-arse acidare regulated in such away that the acid is subjected to electrolysis tor about 30 minutes.
The process may also be carried out discontinuously. The following examples serve to illustrate the inventio but they'are' notintended to limit it' theretoi Emmnle 1 3 litres of phosphoric acid (8.085, percent), which contain 40 milligrams of arsensic per kilogram of acid in the form of arsenic compounds, are heatedto 9.0? C. and stirred by means of, a stirrer (3-5 revolutions per second). Into this phosphoric acid are placed as cathode two copper wire gauzes of cylindrical shape which are inserted into each other, and have a height of 13 cuts. 2 -2 d ameter ofi 4 and. BI cms. respectively. Between the ZIcopper wire gauzesai platinum. wire-gauze electrode is placed as. anode. '40. milligrams of copper ions per kilogram of acid in the form of an aqueous copper sulfate. sohltion-as concentrated as possible and 1.8 milligrams of iodine per kilogram. of acid injthe form of an aqueous 0.1 N-solution of iodine 'are'added and. the acid is electrolyzed under 3. volts. and at 5 'amperes." After about 30. minutes the acid'is free from arsenic.'
. rmi e 3 litres of phosphoric acid (SO-8.5 percent) which contain 40 milligrams of arsenic per kilogram of acid in the form of arsenic compounds are heated to 90 C. and stirred by means "offa stirrer, arrangement of the electrodes is' the same, as described in Example 1. 40 milligrams of copper ions per'ki-logram of acid in the form of an aqueous copper-sulfate. solution as concentrated as possible and 1.8 milligrams of iodine per kilogram of acid in the form of an aqueous 0.1 N-po- 'tassium or sodium iodide solution are added and the acid is electrolyzed wide the sane q ndi pns described in Example 1. A phosphoric acid which is free from arsenic sobta n d Emmy? 3 3: litres of phosphoric acid (-80-85percent) which contain- 4.0v milligrams 'ofi arsenic "per "kilo ram of 'a'cid in the form of arsenic compoundsare heated-Q90 C. and stirred. by means. of a stirrer. The afrangement ofthe electrodes is thesame as described 1 40 milligrams of copperpe'r kilogranioff-acid e form of! dry. copper phosphate and"l.'8' milligrams of iodine per kilogram of-acid in 'the form of an aqueous 0L1" N- iodine: solution are then added and the acidis eleotrolyzed :as. described in Example 1. 'A phbsphorlc acid which is "free from: arsenic is obtained; i
B t- 1 13. 4 3 litres of phosphoric acid (.80 '-85-percent)-which contain 4,Q milligrams. of arsenic per: kilogram of acid in the form of arsenic compounds are heated; to,90- crane stirred: by meansf of a stirrer. The arrangement ofthe electrodes. is the same as'de'scribed in Example 1-." 40 of copper per. kilogram" ofi acid in the form of dry copper phosphate and 1.8 milligrams of iodine per kilogram of acid in the form of an aqueous 0.1 N-solution of potassium or sodium iodide solution are added and the acid is electrolyzed under the same conditions as described in l jigample l. A phosphoric acid which is free from arsenic i's obtained.
We claim: a
P QI o l mina i arse i ompoun from phosphoric acid by electrolysis, in which .the electrolysis is'oarried out with a phosphoric acid which, at the commenee'ment r the deposition, contains arsenic. and copper' in a proportion by weight ranging from between about lziabout 0.2 to about l:about 5,' and copper and iodine in a proportion by. weight ranging. from between about 4010,6to 40 23.0.
2.A process of eliminating arsenic compounds from phosphoric acid by electrolysis, in which the electrolysis is carried out with a phosphoric acid which contains a soluble copper salt in such a quantity that, at the commencement ofthe deposition, the proportion by weight ofarsenic to copper. ranges from between about 1:about 0.2 tov about liabout 5, and. which contains iodine in such a quantity that the propbrtionby weight. of copper to iodine ranges from between 40:0.6 to 4013.0.
3. A'procss. of eliminating arsenic compounds from phosphoric acid. by electrolysis, in which the electrolysis is. carried out with a phosphoric acid which, at the commencement of the deposition, contains arsenic and copper in'a proportion by weight ranging from between about l z-about 0.2 to about lzabout 5, and in which an iodine solution is. added to-the phosphoric acid insuch a quantity. that the proportion by weight of copper to iodine ranges from. between about 40:06 to 40:30.
4; A process ofeliminating-arsenic compounds from phosphoric acid by electrolysis, in which the electrolysis I iscarried' out with a phosphoric acid which, at the com-' mencement of the deposition, contains arsenic and copper in a proportion by weightranging from between about l:'about0.2'to about lfabout 5 and in which the desired iodine content is attained by 'the formation of iodine "front iodides during the reaction, these iodides being added to the phosphoric :acid in such a quantity that copper and iodine are present in a proportion by weight ran'ging from betweenabout 40-:0.-6 to 40:3.0.
SPA process of eliminating arsenic compounds from phosphoric acid by electrolysis, in which the electrolysis is'carried out with a phosphoric acid which, at the com= mencement of the deposition, contains arsenic and: copper'in a proportion by weight ranging from between :about 1-:about 0.Z to about l za'bout 5, and in which the desired iodine contentis attained by the formation of iodine firom hydriodic acid during the reaction, the hydriodie acid being -addedto the phosphoricacid in such a quantity that'copperand ia'dirie are present in; a proportionby weight ranging rmmbetween 4020.6 to 4023.0. f
' No references cited.
Claims (1)
1. A PROCESS OF ELIMINATING ARSENIC COMPOUNDS FROM PHOSPHORIC ACID BY ELECTROLYSIS, IN WHICH THE ELECTROLYSIS IS CARRIED OUT WITH A PHOSPHORIC ACID WHICH, AT THE COMMENCEMENT OF THE DEPOSITION, CONTAINS ARSENIC AND COPPER IN A PROPORTION BY WEIGHT RANGING FROM BETWEEN ABOUT 1:ABOUT 0.2 TO ABOUT 1:ABOUT 5, AND COPPER AND IODINE IN A PROPORTION BY WEIGHT RANGING FROM BETWEEN ABOUT 40:0.6 TO 40:3.0.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE774709X | 1953-09-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US2767136A true US2767136A (en) | 1956-10-16 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US453295A Expired - Lifetime US2767136A (en) | 1953-09-02 | 1954-08-31 | Process of eliminating arsenic compounds from phosphoric acid |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US2767136A (en) |
| FR (1) | FR1107034A (en) |
| GB (1) | GB774709A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5100639A (en) * | 1990-03-02 | 1992-03-31 | E. I. Du Pont De Nemours And Company | Process for purifying hydrogen fluoride |
| CN104261902A (en) * | 2014-09-26 | 2015-01-07 | 安徽淮化股份有限公司 | Acid mixing equipment and method for industrially producing urea and ammonium nitrate solution |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB0711302D0 (en) * | 2007-06-12 | 2007-07-25 | Buss Chemtech Ag | Process & apparatus |
-
1954
- 1954-08-31 US US453295A patent/US2767136A/en not_active Expired - Lifetime
- 1954-08-31 GB GB25312/54A patent/GB774709A/en not_active Expired
- 1954-09-02 FR FR1107034D patent/FR1107034A/en not_active Expired
Non-Patent Citations (1)
| Title |
|---|
| None * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5100639A (en) * | 1990-03-02 | 1992-03-31 | E. I. Du Pont De Nemours And Company | Process for purifying hydrogen fluoride |
| CN104261902A (en) * | 2014-09-26 | 2015-01-07 | 安徽淮化股份有限公司 | Acid mixing equipment and method for industrially producing urea and ammonium nitrate solution |
Also Published As
| Publication number | Publication date |
|---|---|
| FR1107034A (en) | 1955-12-27 |
| GB774709A (en) | 1957-05-15 |
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