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(19) TZZ _Z _T

(11) EP 2 751 028 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention (51) Int Cl.: of the grant of the patent: C01D 3/06 (2006.01) C01D 3/08 (2006.01) 09.12.2015 Bulletin 2015/50 (86) International application number: (21) Application number: 13722048.9 PCT/IB2013/000582

(22) Date of filing: 02.04.2013 (87) International publication number: WO 2013/150363 (10.10.2013 Gazette 2013/41)

(54) SELECTIVE EXTRACTION OF CHLORIDE FROM SCHOENITE END LIQUOR EMPLOYING TARTARIC AS SAFE, BENIGN AND RECYCLABLE EXTRACTANT SELEKTIVE EXTRAKTION VON KALIUMCHLORID AUS SCHÖNIT- ENDFLÜSSIGKEIT MIT EINER WEINSÄURE ALS SICHEREM, GUTARTIGEM UND WIEDERVERWENDBAREM EXTRAKTIONSMITTEL EXTRACTION SÉLECTIVE DE CHLORURE DE POTASSIUM À PARTIR D’UNE LIQUEUR FINALE DESCHOENITE UTILISANT DE L’ACIDE TARTRIQUE COMME AGENT D’EXTRACTION SÛR, SANS DANGER ET RECYCLABLE

(84) Designated Contracting States: • SOLANKI, Jignesh AL AT BE BG CH CY CZ DE DK EE ES FI FR GB Bhavnagar 364 021 Gujarat (IN) GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO • BRAHMBHATT, Harshad, Raman PL PT RO RS SE SI SK SM TR Bhavnagar 364 021 Gujarat (IN) • CHUNAWALA, Jatin, Ramesh (30) Priority: 02.04.2012 IN DE06062012 Bhavnagar 364 021 Gujarat (IN) • ERINGATHODI, Suresh (43) Date of publication of application: Bhavnagar 364 021 Gujarat (IN) 09.07.2014 Bulletin 2014/28 • PAUL, Parimal Bhavnagar 364 021 Gujarat (IN) (73) Proprietor: Council of Scientific & Industrial Research (74) Representative: Fairbairn, Angus Chisholm New Delhi 110 001 (IN) Marks & Clerk LLP 90 Long Acre (72) Inventors: London • MAITI, Pratyush WC2E 9RA (GB) Bhavnagar 364 021 Gujarat (IN) • GHOSH, Pushpito Kumar (56) References cited: Bhavnagar 364 021 Gujarat (IN) WO-A1-2007/054953 WO-A1-2008/020457 • GHARA, Krishna, Kanta DE-C- 694 480 US-A- 2 617 710 Bhavnagar 364 021 Gujarat (IN) US-A- 2 710 789 US-B2- 7 041 268

Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 2 751 028 B1

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Description implementation of the process poses serious operational & environmental issues owing to hazardous nature of FIELD OF THE INVENTION dipicryl amine. [0007] Thus a need was felt to devise a process to [0001] The present invention provides safe and effi- 5 selectively extract potassium from bittern & other K bear- cient extraction process for the recovery of near saturat- ing aqueous solutions for production of potassic fertiliser ed solution of KC1, free of impurities useful for production using a recyclable, benign & environmentally safe ex- of sulphate of potash (SOP) and sulphate tractant. using bittern, ammonia & hydrochloric acid as raw ma- [0008] It was quite well known that potassium terials and employing as the safe, benign, 10 (cream of tartar) has substantially lower than recyclable & selective extractant for recovery of potassi- bitartrate. Cream of tartar, a derivative of wine um from intermediate process stream. More particularly, industry attracted lot of attention, particularly in regard to the invention eliminates the need for natural/solar evap- recovery of tartaric acid & potassium . oration of intermediate streams for recovery of potassium [0009] Reference may be made to US patent no. chloride and thereby reduces dependency on seasonal 15 957,295, May 10, 1910 by Alberti A. et al. which teaches weather variations & land resources. Further the present about process of recovering potash salts from wine lye invention derives beneficial synergies and advantages (raw cream of tartar). Reference may be made to US of integrated approach of the process. patent no. 2,710,789, June 14, 1955 by Boeri G. et al. which teaches about method for preparing substantially BACKGROUNDAND PRIOR ARTOF THE INVENTION 20 pure potassium nitrate from raw tartaric materials. [0010] Reference may be made to US patent no. [0002] Potassium bearing aqueous solutions, viz., sea 3,069,230, Dec 18, 1962 by Pescarolo B. et al. which bittern left after recovery of common in solar salt work teaches about process for extracting Tartaric Acid and is a rich source of the element (20-25 g/lit potassium chlo- Potassium in form pure potassium nitrate in the cold from ride). Similarly, the natural bittern of Greater Rann of25 tartaric acid, without the need of previous roasting of the Kutchh (Gujarat, India) is a perennial source of potassi- tartaric raw material. um. Evaporite based technologies rely on solar evapo- [0011] The above mentioned inventions used wine ration of bittern and require large amount of land area lees (raw cream of tartar - crude potassium bitartrate) as apart from favourable climatic conditions for consistent the potash bearing raw material. Moreover, the aforesaid production of the potassic feedstock. 30 patents do not teach us about recycling of the extractant, [0003] Reference may be made to U S patenti.e., tartaric acid. 7,041,268, May 9, 2006 by Ghosh P. K. et al. which teach- [0012] Reference may be made to the paper "Adapta- es about an integrated process for the recovery of sul- tion of the bitartrate method for the estimation of potas- phate of potash (SOP) from sulphate rich bittern. How- sium in sea bittern" by Shukla, B. K. et.al (http://www.csir- ever, this process depends on evaporation of intermedi- 35 central.net/index.php/record/view/88029) which teaches ate streams for production of , re- about the method for estimation of potassium content of quired in the process. This creates additional demand bittern, by precipitating potassium as potassium for large amount of land area apart from need effective bitartrate. Although developed as a method for analysis, integration of plant & field operations. the main disadvantages for practising this process are [0004] Selective extraction of potassium offers a prac- 40 that it requires addition of methanol/, & sodium tical & implementable alternative to overcome the afore- hydrogen apart from tartaric acid for precipitation mentioned impediments faced by evaporite based tech- of potassium bitartrate. nologies. [0005] Reference may be made to U S patentOBJECTS OF THE INVENTION 2,617,710, Nov 11, 1952 by Kielland J. et al. which teach- 45 es an efficient method for extraction of potassium from [0013] The main object of the invention is to devise a dilute solution, e.g., sea water, using dipicryl amine as safe and efficient extraction process for the recovery of extractant. However, commercial implementation of the near saturated KCl solution, free of impurities, from sch- process poses serious operational & environmental is- oenite end liquor (SEL), obtained from the decomposition sues owing to hazardous nature of dipicryl amine. 50 of kainite mixed salt into schoenite as disclosed in the [0006] Reference may be made to WO-A-prior art, thereby eliminating the need for i) evaporation 2007/054953 (U S patent 8,182,784, May 22, 2012 by of intermediate process stream, i.e., SEL and ii) down- Paul P. et al.) which teaches an efficient method for ex- stream processes for recovery of potassium chloride, traction of potassium from SEL, the potassium rich inter- viz., evaporite harvesting, carnallite decomposition, hot mediate stream generated upon decomposition of kainite 55 leaching of crude potash etc. type mixed salt, as described in U S patent 7,041,268, [0014] Another object is to selectively precipitate po- in the form of potassium chloride, using dipicryl amine tassium from SEL, as potassium bitartrate, with high re- as extractant. However, in this instance also, commercial covery efficiency.

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[0015] Another object is to use tartaric acid and salts Figure 1 represents improved process for recovery thereof as safe, benign and recyclable extractant. of sulphate of potash (SOP) from kainite mixed salt [0016] Another object is to take advantage of optically with selective extraction of potassium chloride from active isomers of tartaric acid to reduce impurity in po- schoenite end liquor employing tartaric acid as safe, tassium bitartrate & to enhance recovery of near saturat- 5 benign and recyclable extractant. ed KCl solution from solid potassium bitartrate. Figure 2 represents process for recovery of residual [0017] Another object is to carry out the core process tartaric acid from intermediate streams. steps at ambient temperature. [0018] Anotherobject isto generate near saturatedKCl SUMMARY OF THE INVENTION solution, by reacting potassium bitartrate with magnesi- 10 um hydroxide & . [0029] Accordingly, present invention provides a safe [0019] Another object is to reuse the magnesium tar- and efficient extraction process for the recovery of near trate, obtained during production of near saturated KCl saturated solution of potassium chloride (KCl), free of solution, for subsequent cycles of selective precipitation impurities wherein said process comprises the steps of: of potassium from SEL. 15 [0020] Another object is to selectively precipitate po- i. providing schoenite end liquor (SEL) containing tassium from potassium rich aqueous solutions, includ- 4.0-5.5% w/v K + obtained from the decomposition of ing but not limited to, bittern, seaweed Kappaphycus( kainite mixed salt into schoenite by known method; alvarezii) sap etc., as potassium bitartrate. treating schoenite end liquor containing 4.0-5.5% [0021] Another object is to minimise tartaric acid loss 20 w/v K+ as obtained in step (i) with a sub-stoichiomet- in the potassium depleted SEL & potassium bitartrate ric amount of tartaric acid half-neutralized with washings by precipitating the same as calcium tartrate, Mg(OH)2, to obtain potassium bi-tartrate and potas- using calcium carbonate, , gypsum etc. sium depleted schoenite end liquor; [0022] Another object is to minimise tartaric acid im- ii. separating out and washing the precipitated po- purity in the near saturated KCl solution by precipitating 25 tassium bi-tartrate as obtained in step (ii) with water; the same as calcium tartrate, using calcium chloride, gyp- iii. adding the washings into the potassium-depleted sum etc. schoenite end liquor; [0023] Another object is to reuse the washings of mag- iv. treating the potassium bi-tartrate as obtained in nesium tartrate in subsequent batches of production of step (iii) with stoichiometric amount of MgCl2 and 30 near saturated KCl solution to enhance recovery of po- Mg(OH)2 to convert it into magnesium tartrate while tassium chloride in concentrated form. releasing the potassium into solution as near satu- [0024] Another object is to use magnesium chloride rated potassium chloride; rich end bittern, obtained upon complete crystallisation v. washing the magnesium tartrate as obtained in of kainite type mixed salt in course of evaporation of sea step (v) and separately preserving the washing; bittern, with potassium bitartrate & magnesium hydroxide 35 vi. treating the K-depleted schoenite end liquor as to produce near saturated KCl solution. Another object obtained in step (iv) and the potassium chloride so- is to use the potassium depleted SEL, after recovery of lution obtained in step (v) with calcium carbonate residual tartaric acid, for production of magnesium hy- and calcium chloride to precipitate out residual tar- droxide which in turn will be used in the production of taric acid in the form of insoluble calcium tartrate; near saturated KCl solution. 40 vii. adding the magnesium tartrate of step (v) into a [0025] Another object is to minimise the need for out- fresh lot of schoenite end liquor SEL along with sto- sourced calcium carbonate, required in the process for ichiometric amount of aqueous HCl to once again recovery of residual tartaric acid from different process precipitate out potassium bi-tartrate; streams, by obtaining the same through integrated pro- viii. adding the potassium bitartrate from step (viii) duction of ammonium sulphate besides SOP. 45 into the washing of step (vi) and additional amount [0026] Another object is to produce multi-nutrient fer- of water as required followed by treating with stoi- tilisers as of sulphate of potash & ammonium sulphate. chiometric amounts of MgCl2 and Mg(OH)2 to once [0027] Another object is to produce desirable potassi- again precipitate out magnesium tartrate and obtain- um salts, viz., potassium chloride, potassium sulphate, ing once again a near saturated solution of KCl Po- potassium nitrate, potassium phosphate, potassium car- 50 tassium chloride followed by regenerating tartaric bonate etc., by reacting the precipitated potassium acid from calcium tartrate obtained in step (vii). bitartrate with magnesium hydroxide or magnesium car- bonate & appropriate magnesium salts. [0030] In another embodiment of the invention, the tar- taric acid is in the racemic or optically active form and BRIEF DISCRIPTION OF THE DRAWINGS 55 preferably in the form of L-isomer. [0031] In another embodiment of the invention, the tar- [0028] taric acid is in pure form or salt form. [0032] In another embodiment of the invention, the

3 5 EP 2 751 028 B1 6 schoenite end liquor containing 4.0-5.5% w/v K + is treat- nesium phosphate or magnesium carbonate respectively ed with a sub-stoichiometric amount of tartaric acid half- in place of MgCl2. neutralized with Mg(OH)2, at a temperature in the range [0046] In another embodiment of the invention, the sat- of 20 to 35°C. urated potassium chloride solution produces sulphate of [0033] In another embodiment of the invention, the 5 potash on reaction with schoenite. amounts of L-tartaric acid and magnesium L-tartrate used in steps (ii) and (viii), respectively, are in the range DETAILED DESCRIPTION OF THE INVENTION of 85-95% (molar basis) of the amount of K+ in schoenite end liquor. [0047] The present invention provides a safe and effi- [0034] In another embodiment of the invention, sea- 10 cient extraction process for the recovery of near saturat- weed sap fromKappaphycus alvarezi containing ed solution of KCl, free of impurities, from schoenite end 3.0-4.5% w/v potassium chloride is alternatively used in liquor (SEL) obtained from the decomposition of kainite place of schoenite end liquor to obtain potassium mixed salt into schoenite as disclosed in the prior art, bitartrate with similar efficiency. such process comprising (i) treating SEL containing [0035] In another embodiment of the invention, sea bit- 15 4.0-5.5% w/v K+ with a sub-stoichiometric amount of tar- tern is used in place of schoenite end liquor to obtain taric acid half-neutralized with Mg(OH) 2, at room temper- potassium bitartrate. ature; (ii) separating out and washing the precipitated [0036] In another embodiment of the invention, recov- potassium bi-tartrate with water; (iii) adding the washings ery of potassium L-bitartrate from sea bittern having into the K-depleted SEL; (iv) treating the potassium bi- 20 3.25% w/v KCl was only 54-58%, i.e., other constituents tartrate with stoichiometric amount of 2 MgCl and in the solution can have a profound influence on recovery Mg(OH)2 to convert it into magnesium tartrate while re- and the compositions of SEL and sap are better suited leasing thepotassium into solutionas near saturatedKCl; for practice of the invention. (v) washing the magnesium tartrate and separately pre- [0037] In another embodiment of the invention, recov- serving the washing; (vi) treating the K-depleted SEL ob- ery of potassium bitartrate was 85-95% on molar basis 25 tained in step (iii) and the KCl solution obtained in step with respect to L-tartaric acid and magnesium L-tartrate (iv) with calcium carbonate and calcium chloride to pre- used in steps (ii) and (viii), respectively. cipitate out residual tartaric acid in the form of insoluble [0038] In another embodiment of the invention, recov- calcium tartrate; (vii) adding the magnesium tartrate of ery of magnesium tartrate with respect to potassium step (iv) into a fresh lot of SEL along with stoichiometric bitartrate was 85-95% in step (v). 30 amount of aqueous HCl to once again precipitate out [0039] In another embodiment of the invention, the potassium bi-tartrate; (viii) adding the potassium washing of magnesium tartrate, contained 7-9% KCl in bitartrate from step (vii) into the washing of step (v) and the case of L-tartaric acid and 14-16% for DL isomer of additional amount of water as required and treating with tartaric acid, indicating more efficient dewatering of the stoichiometric amounts of MgCl2 and Mg(OH)2 to once slurry after the reaction of step (v). 35 again precipitate out magnesium tartrate and obtaining [0040] In another embodiment of the invention, in step once again a near saturated solution of KCl; (ix) regen- (vii), residual tartaric acid content is reduced to 200 - 400 erating tartaric acid from calcium tartrate obtained in step ppm. (vi) through known prior art; (x) reacting the saturated [0041] In another embodiment of the invention, in step KCl solution obtained above with schoenite to produce (iv), end bittern obtained after recovery of kainite mixed 40 sulphate of potash through the known prior art. salt is used in place of pure MgCl 2. [0048] Room temperature varied from 24-26°C. [0042] In another embodiment of the invention, the HCl [0049] Compared to the DL isomer, the L-isomer of and MgO/Mg(OH) 2 required in steps (ii), (v) and (viii) can tartaric acid gave higher recovery of filtrate both luring be generated from MgCl2 using known methods dis- formation of potassium bitartrate and its subsequent de- closed in the prior art. 45 composition to release KCl and precipitate out magnesi- [0043] In another embodiment of the invention, um tartrate.

Mg(OH)2 required in the process of steps (ii) and (v) can [0050] Amounts of L-tartaric acid and magnesium L- be alternatively generated as part of the integrated proc- tartrate used in steps (i) and (vii), respectively, were 90% esses for sulphate of potash recovery from kainite mixed (molar basis) of the amount of K + in SEL. salt. 50 [0051] Seaweed sap containing 3.25% w/v KCl, as ob- [0044] In another embodiment of the invention, calci- tained from Kappaphycus alvarezii, was used n place of um carbonate required in the process of step (vii) can be SEL resulting in precipitation of potassium bitartrate in obtained from integrated production of sulphate of potash 88% efficiency on molar basis with respect to L-tartaric and ammonium sulphate from kainite mixed salt. acid. [0045] In yet another embodiment of the invention, po- 55 [0052] The yield of potassium L-bitartrate was 55% on tassium sulphate, potassium nitrate, potassium phos- molar basis with respect to L-tartaric acid when sea bit- phate or , are generated in step (v) tern having 3.25% w/v KCl was used. by using magnesium sulphate, magnesium nitrate, mag- [0053] Recovery of potassium bitartrate was 88% on

4 7 EP 2 751 028 B1 8 molar basis with respect to L-tartaric acid and magnesi- vi. Another inventive step is the recognition that the um L-tartrate used in steps (i) and (vii), respectively. decomposition of potassium bitartrate can be carried [0054] Recovery of magnesium L-tartrate with respect out in a manner that allows one to have access to a to potassium bitartrate was 88% in step (iv). Residual wide variety of potassium salts besides potassium tartaric acid content in the potassium-depleted SEL was 5 chloride. reduced below 300 ppm in step (vi) and the loss of tartaric acid/kg of KCl obtained was estimated to be 4.28 g. [0061] The following examples are given by way of il- [0055] Residual tartaric acid in the KCl solution re- lustration and therefore should not be construed to limit mained in the mother liquor during the reaction with sch- the scope of the present invention. oenite to generate SOP. 10 [0056] End bittern after recovery of kainite mixed salt Example 1 may be used in place of pure MgCl 2 in step (iv). [0057] The HCl and MgO/Mg(OH)2 required in steps [0062] 1 L of SEL [K: 4.83% w/v (1.24 mol), Na: 5.7% (i), (iv) and (vii) can be generated from MgCl2 using w/v (2.48 mol)] was reacted with 167.12 gm (1.11 mol) known methods disclosed in the prior art. 15 DL-tartaric acid and 32.5 gm of magnesium hydroxide [0058] Mg(OH) required in the process of step (i) and 2 (0.56 mol) under stirring for 22 hrs at 25 6 1 C. The (iv) can be generated as part of the integrated processes final pH was 1.30. Upon filtration of the resultant slurry, for sulphate of potash recovery from kainite mixed salt 810 mL filtrate [K = 0.20% w/v (0.04 mol)] and a wet solid known in the prior art. Calcium carbonate required in the was obtained, which was washed with 100 mL water & process of step (vi) can be obtained from integrated pro- 20 dried to obtain 291 gm of product with 15.46% K and duction of sulphate of potash and ammonium sulphate 0.59% Na content. from kainite mixed salt. [0059] Other salts of potassium such as potassium sul- Example 2 phate, nitrate, phosphate, carbonate, etc. can be gener- ated in step (iv) by using appropriate magnesium salts 25 [0063] The experiment of Example 1 was repeated ex- in place of MgCl . 2 cept that DL-tartaric acid was replaced with L-tartaric ac- id. The final pH was 1.26. 910 mL filtrate [K = 0.22% w/v Inventive Steps (0.05 mol), tartaric acid = 2.38% (w/v) (0.14 mol)] and 193 gm of solid containing 22% K and 0.24% Na was [0060] 30 obtained. The K content matched reasonably with the expected value of 20.74% K for potassium bitartrate. i. The main inventive step is the finding that whereas [0064] Examples 1 and 2 above teach us the method recovery of potassium bitartrate is only moderate for of precipitation of potassium from SEL, as potassium even concentrated bittern having 3.5-4.0 % w/v KCl, bitartrate, with lower retention of mother liquor, using the it is remarkably high for the specific systems of in- 35 combination of L-tartaric acid and Mg(OH) . The data of terest, namely SEL and seaweed sap, even when 2 such extraction is undertaken under ambient condi- Example 2 further indicate that residual tartrate in the tions. filtrate is only 12% of the amount taken even when the ii. Another inventive step is the discovery that potas- reaction is conducted at room temperature (25 1C).6 sium bitartrate and magnesium tartrate made from 40 Further, the observed weight (193 g) of potassium DL (racemic) and L (optically active) tartaric bitartrate matches well with the 88% recovery for which do not behave in the same way and the latter is a the computed yield is 184 g. This data in combination better choice for easy practice of the invention. with the data on K percentage indicate satisfactory purity iii. Another inventive step is the transformation of of the product, the small discrepancy possibly being due solid potassium bitartrate into solid magnesium tar- 45 to adhering salts which remained after washing. trate under ambient conditions using benign chem- Example 3 icals such as MgCl 2 and Mg(OH) 2, with concomitant formation of a nearly saturated KCl solution. iv. Another inventive step is the recognition that the [0065] 500mL bittern [K: 1.7% w/v (0.22 mol),Na: 3.4% saturated KCl solution is ideally suited for reaction 50 w/v (0.74 mol)] was reacted with 29.42 gm (0.20 mol) of with schoenite for formation of sulphate of potash, L-tartaric acid & 5.72 gm of magnesium hydroxide (0.10 thereby eliminating the need for recovery of KCl in mol) under stirring for 18 hrs at 256 1 C. The final solid form. pH was 0.7. Upon filtration of the resultant slurry, 505 mL v. Another inventive step is the recovery of residual of filtrate [K = 0.55% w/v (0.07 mol)] & wet solid was tartaric acid from solutions through precipitation in 55 obtained which was further washed with 50 mL water & the form of highly insoluble calcium tartrate and the dried to produce potassium bitartrate [18.8 gm; K: subsequent regeneration of tartaric acid therefrom 22.70% (0.11 mol)]. through known prior art.

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Example 4 for 41 hrs at 25 6 1 C. The final pH was 1.35. Upon filtration of the resultant slurry, 465 mL of filtrate [K = [0066] 400 mL of sap [K = 1.73% w/v (0.18 mol)], ob- 0.61% w/v (0.07 mol); tartaric acid = 1.42% w/v (0.044 tained from red seaweed(Kappaphycus alvarezii, ob- mol)] & a wet solid was obtained, which was washed with tained from Mandapam, Tamilnadu), was reacted with 5 50 mL water & dried to produce 74 gm of potassium L- 23.92 gm (6% w/v; 0.16 mol) of L-tartaric acid & 4.65 gm bitartrate [K = 21.20% (0.40 mol); Na = 0.17% (0.0055 of magnesium hydroxide (0.08 mol) under stirring for 20 mol); tartaric acid = 73.8% (0.36 mol)]. hrs at 25 6 1 C. The final pH was 2.78. Upon filtration [0072] Example 7 teaches us the method of recycling of the resultant slurry, 350 mL of filtrate [K = 0.28% w/v; magnesium tartrate in a fresh lot of SEL through use of tartaric acid: 0.72% w/v] & potassium bitartrate (26 gm; 10 hydrochloric acid for regeneration of bitartrate and con- 88% isolated yield). sequent precipation of potassium bitartrate from SEL. [0067] Examples 2 to 4 teach us that recovery of po- Theyield ofpotassium bitartrate from magnesium tartrate tassium bitartrate from SEL and Kappaphycus alvarezii is computed to be 88% which is the same as the yield seaweed sap at room temperature is much more efficient obtained in Example 2. than with sea bittern (K~1.7% w/v) ( ≥ 88% vs. 56%), other 15 conditions being similar. Example 8

Example 5 [0073] 0.3 L of a potassium depleted bittern containing 1.63% (w/v) residual tartaric acid was reacted with 2.4 [0068] 94 gm pure potassium DL-bitartrate [K = 20% 20 gm (0.024 mol) calcium carbonate (purity:100%) & 1.2 (0.48 mol)] was reacted with 24.71 gm (0.26 mol) of mag- gm (0.0.007 mol) gypsum, under stirring for 1 hr at 25 6 nesium chloride & 14.6 gm of magnesium hydroxide 1 C. The residual tartaric acid in the liquor decreased (0.26 mol), in 150 ml water, under stirring for 17 hrs at to 0.086% (w/v) with concomitant formation of calcium 25 6 1 C. The final pH was 5.0. Upon filtration of the tartrate. resultant slurry, 86 mL of filtrate [K = 11.24% w/v (0.25 25 [0074] 0.1 L of the bittern depleted in tartaric acid was mol)] & wet solid was obtained which was washed with further reacted with 0.5 gm (0.0035 mol) calcium chloride 100 mL water to obtain 100 mL of wash liquor [K = 7.58% (purity:100%) & 10 ml of water, under stirring for 1 hr at w/v (0.19 mol)] and 154 gm of wet magnesium tartrate 25 6 1 C. Upon filtration of the resultant slurry, the [K: 0.46% (0.02 mol)]. tartaric acid content in the filtrate was further reduced to 30 268 ppm. Example 6 [0075] In similar manner, residual tartaric acid in po- tassium depleted SEL of Examples 1 and 2, and in KCl [0069] 94 gm of the dry solid comprising mainly potas- solution of Examples 4 and 5, can be recovered in the sium L-bitartrate obtained in Example 2, was treated with form of highly insoluble calcium tartrate and the tartaric 23.68 gm (0.25 mol) of magnesium chloride & 14.6 gm 35 acid can be regenerated there from following known prior of magnesium hydroxide (0.26 mol), in 150 ml water, un- art. der stirring, for 17 hrs at 25 6 1 C. The final pH was 8.2. Upon filtration of the resultant slurry, 132 mL of filtrate ADVANTAGES OF THE INVENTION [K = 12% w/v (0.41 mol); Na = 0.26% w/v (0.015 mol); tartaric acid = 1.48% w/v; (0.013 mol)] & a wet solid was 40 [0076] The present invention provides a safe and effi- obtained, which was washed with 100 mL water to obtain cient extraction process for the recovery of near saturat- 102 mL of wash liquor [K = 4.4% w/v (0.12 mol)] and 133 ed KCl solution, free of impurities, from schoenite end g of washed wet solid containing 0.83% (w/v) K (0.03 liquor (SEL), obtained from the decomposition of kainite mol) and 7.66% (w/v) Mg (0.42 mol). mixed salt into schoenite as disclosed in the prior art, [0070] Example 5 & 6 above teach us the method of 45 thereby eliminating the need for i) evaporation of inter- recovery of a near saturated solution of potassium chlo- mediate process stream, i.e., SEL and ii) downstream ride from potassium bitartrate with co-generation of solid processes for recovery of potassium chloride, viz., evap- magnesium tartrate. These examples also teach us that orite harvesting, carnallite decomposition, hot leaching magnesium L-tartrate gives higher recovery of filtrate of crude potash etc. than magnesium DL-tartrate and, consequently, the yield 50 [0077] Main advantages of the present invention may of KCl in concentrated form is higher with the former. be stated as follows:

Example 7 i) Compared to dipicrylamine extractant used previ- ously for KC1 recovery from SEL, tartaric acid is a [0071] 406 mL of SEL [K = 4.83% w/v (0.5 mol), Na = 55 safe extractant. Tartaric acid and salts thereof were 5.7% w/v (1.01 mol)] was reacted with 45.2 mL (0.45 mol) is in the racemic or optically active forms and pref- of hydrochloric acid & 130 gm of magnesium L-tartrate erably in the form of the L-isomer, which is affordably [Mg = 7.66%, (0.41 mol)] from Example 4 under stirring priced and, compared to the racemate, gave higher

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recovery of filtrate both during formation of potassi- v. treating the potassium bi-tartrate as obtained um bitartrate and its subsequent decomposition to in step (iii) with stoichiometric amount of MgCl 2 release KCl in solution. and Mg(OH)2 to convert it into magnesium tar- ii) Whereas complete decomposition of the potassi- trate while releasing the potassium into solution um salt of dipicrylamine in the KCl forming process 5 as near saturated potassium chloride; was difficult, and required a second treatment with vi. washing the magnesium tartrate as obtained nitric acid, this was not the case in the present sys- in step (v) and separately preserving the wash- tem. ing; iii) Whereas recovery of potassium bitartrate was rel- vii. treating the K-depleted schoenite end liquor atively low for bittern systems, it was remarkably ef- 10 as obtained in step (iv) and the potassium chlo- ficient for the compositions of interest, namely sch- ride solution obtained in step (v) with calcium oenite end liquor (SEL) and seaweed sap, especially carbonate and calcium chloride to precipitate with L-tartaric acid. out residual tartaric acid in the form of insoluble iv) The core steps of the process, namely formation calcium tartrate; of potassium bitartrate and decomposition of the15 viii. adding the magnesium tartrate of step (v) same, with regeneration of the extractant, can be into a fresh lot of schoenite end liquor SEL along performed under ambient conditions. with stoichiometric amount of aqueous HCl to v) Chemicals such as HCl, magnesium hydroxide once again precipitate out potassium bi-tartrate; and magnesium chloride required in the process can ix.adding the potassiumbitartrate from step(viii) all be obtained as part of the process. 20 into the washing of step (vi) and additional vi) By dispensing with the need of fractional - amount of water as required followed by treating lization as the means of recovery of KCl from SEL, with stoichiometric amounts of MgCl2 and the entire process of producing sulphate of potash Mg(OH)2 to once again precipitate out magne- from kainite mixed salt can be performed through in- sium tartrate and obtaining once again a near plant operations. 25 saturated solution of KCl Potassium chloride fol- vii) Losses of tartaric acid during recovery can be lowed by regenerating tartaric acid from calcium eliminated by taking advantage of the low solubility tartrate obtained in step (vii). of calcium tartrate and subsequent recovery of tar- taric acid from it through known process. 2. The process as claimed in claim 1, wherein in step viii) When seaweed sap which contains KCl is used, 30 (ii) the tartaric acid is in the racemic or optically active the process of the invention enables its concentra- form and preferably in the form of L-isomer. tion to be enhanced to saturation levels without re- quirement of thermal energy. 3. The process as claimed in claim 1, wherein in step ix) The invention allows easy access to other impor- (ii) the tartaric acid is in pure form or salt form. tant salts of potassium. 35 4. The process as claimed in claim 1, wherein in step (ii), the schoenite end liquor containing 4.0-5.5% w/v Claims K+ is treated with a sub-stoichiometric amount of tar- taric acid half-neutralized with Mg(OH)2, at a tem- 1. A safe and efficient extraction process for the recov- 40 perature in the range of 20 to 35°C. ery of near saturated solution of potassium chloride, free of impurities wherein said process comprises 5. The process as claimed in claim 1 and 2, wherein the steps of: the amounts of L-tartaric acid and magnesium L-tar- trate used in steps (ii) and (viii), respectively, are in i. providing schoenite end liquor (SEL) contain- 45 the range of 85-95% (molar basis) of the amount of ing 4.0-5.5% w/v K+ obtained from the decom- K+ in schoenite end liquor. position of kainite mixed salt into schoenite; ii. treating schoenite end liquor containing 6. The process as claimed in claim 1, wherein in step 4.0-5.5% w/v K+ as obtained in step (i) with a (ii), seaweed sap from Kappaphycus alvarezi con- sub-stoichiometric amount of tartaric acid half- 50 taining 3.0-4.5% w/v potassium chloride is alterna- neutralized with Mg(OH)2, to obtain potassium tively used in place of schoenite end liquor to obtain bi-tartrate and potassium depleted schoenite potassium bitartrate with similar efficiency. end liquor; iii. separating out and washing the precipitated 7. The process as claimed in claim 1, wherein in step potassium bi-tartrate as obtained in step (ii) with 55 (ii), sea bittern is used in place of schoenite end liquor water; to obtain potassium bitartrate. iv. adding the washings into the potassium-de- pleted schoenite end liquor; 8. The process as claimed in claim 7, wherein recovery

7 13 EP 2 751 028 B1 14

of potassium L-bitartrate from sea bittern having Patentansprüche 3.25% w/v KCl was only 54-58%, i.e., other constit- uents in the solution can have a profound influence 1. Unbedenkliches und effizientes Extraktionsverfah- on recovery and the compositions of SEL and sap ren zum Gewinnen einer fast gesättigten Lösung von are better suited for practice of the invention. 5 Kaliumchlorid, die frei von Verunreinigungen ist, wo- bei das Verfahren die Schritte umfasst des: 9. The process as claimed in claim 1 and 2, wherein recovery of potassium bitartrate was 85-95% on mo- i. Bereitstellens von Schönit-Endflüssigkeit lar basis with respect to L-tartaric acid and magne- (SEF), die 4,0-5,5 Gew./Vol.-% K+ enthält und sium L-tartrate used in steps (ii) and (viii), respec- 10 aus der Zersetzung von Kainitmischsalz zu tively. Schönit erhalten wird; ii. Behandelns der Schönit-Endflüssigkeit, die 10. The process as claimed in claim 1, wherein recovery 4,0- 5,5 Gew./Vol.-% K+ enthält, wie in Schritt of magnesium tartrate with respect to potassium (i) erhalten, mit einer substöchiometrischen 15 bitartrate was 85-95% in step (v). Menge Weinsäure, die mit Mg(ON) 2 halbneutra- lisiert worden ist, um Kaliumbitartrat und an Ka- 11. The process as claimed in claim 1 and 2, wherein lium verarmte Schönit-Endflüssigkeit zu erhal- the washing of magnesium tartrate, contained 7-9% ten; KCl in the case of L-tartaric acid and 14-16% for DL iii. Abtrennens und Waschens des ausgefällten isomer of tartaric acid, indicating more efficient de- 20 Kaliumbitartrats, wie in Schritt (ii) erhalten, mit watering of the slurry after the reaction of step (v). Wasser; iv. Zugebens der Waschflüssigkeiten zu der an 12. The process as claimed in claim 1, wherein in step Kalium verarmten Schönit-Endflüssigkeit; (vii) residual tartaric acid content is reduced to 200 v. Behandelns des Kaliumbitartats, wie in Schritt - 400 ppm. 25 (iii) erhalten, mit einer stöchiometrischen Menge MgCl2 und Mg(OH)2, um es zu Magnesiumtar- 13. The process as claimed in claim 1, wherein in step trat umzuwandeln, während das Kalium in Lö- (iv) end bittern obtained after recovery of kainite sung als fast gesättigtes Kaliumchlorid freige-

mixed salt is used in place of pure MgCl 2. setzt wird; 30 vi. Waschens des Magnesiumtartrats, wie in 14. The process as claimed in claim 1, wherein the HCl Schritt (v) erhalten, und getrennten Konservie- and MgO/Mg(OH)2 required in steps (ii), (v) and (viii) rens der Waschflüssigkeit; can be generated from MgCl 2 using known methods vii. Behandelns der an K verarmten Schönit- disclosed in the prior art. Endflüssigkeit, wie in Schritt (iv) erhalten, und 35 der in Schritt (v) erhaltenen Kaliumchloridlösung

15. The process as claimed in claim 1, wherein Mg(OH) 2 mit Calciumcarbonat und Calciumchlorid, um required in the process of steps (ii) and (v) can be restliche Weinsäure in Form von unlöslichem alternativelygenerated as partof the integrated proc- Calciumtatrat auszufällen; esses for sulphate of potash recovery from kainite viii) Eingebens des Magnesiumtartrats aus mixed salt. 40 Schritt (v) zu einer frischen Charge Schönit- Endflüssigkeit SEH zusammen mit einer stöchi- 16. The process as claimed in claim 1, wherein calcium ometrischen Menge wässriger HCl, um Kalium- carbonate required in the process of step (vii) can bitartrat nochmals auszufällen; be obtained from integrated production of sulphate ix. Eingebens des Kaliumbitartrats aus Schritt of potash and ammonium sulphate from kainite45 (viii) in die Waschflüssigkeit aus Schritt (vi) und mixed salt. einer zusätzlichen Menge Wasser, wie erforder- lich, danach das Behandeln mit stöchiometri-

17. The process as claimed in claim 1, wherein potassi- schen Mengen MgCl2 und Mg(OH)2, um Mag- um sulphate, potassium nitrate, potassium phos- nesiumtartrat nochmals auszufällen und noch- phate or potassium carbonate, are generated in step 50 mals eine fast gesättigte Lösung von KCl Kali- (v) by using magnesium sulphate, magnesium ni- umchlorid zu erhalten, gefolgt vom Regenerie- trate, magnesium phosphate or magnesium carbon- ren von Weinsäure aus in Schritt (vii) erhaltenem

ate respectively in place of MgCl2. Calciumtartrat.

18. The process as claimed in claim 1, wherein the sat- 55 2. Verfahren nach Anspruch 1, wobei in Schritt (ii) die urated potassium chloride solution produces sul- Weinsäure in racemischer oder optisch aktiver Form phate of potash on reaction with schoenite. und bevorzugt in Form von L-Isomer vorliegt.

8 15 EP 2 751 028 B1 16

3. Verfahren nach Anspruch 1, wobei in Schritt (ii) die der Gewinnung von Kainitmischsalz erhaltene rest- Weinsäure in reiner Form oder Salzform vorliegt. liche Endmutterlauge aus der Meersalzgewinnung statt reines MgCl2 verwendet wird. 4. Verfahren nach Anspruch 1, wobei in Schritt (ii) die Schönit-Endflüssigkeit, die 4,0- 5,5 Gew./Vol.-% K+ 5 14. Verfahren nach Anspruch 1, wobei das HCl und enthält, mit einer substöchiometrischen Menge MgO/Mg(OH)2, die in den Schritten (ii), (v) und (viii) Weinsäure, die mit Mg(OH)2 halbneutralisiert wor- benötigt werden, aus MgCl2 unter Anwendung be- den ist, bei einer Temperatur im Bereich von 20 bis kannter Verfahren, die im Stand der Technik offen- 35 °C behandelt wird. bart sind, erzeugt werden können. 10

5. Verfahren nach Anspruch 1 und 2, wobei die Mengen 15. Verfahren nach Anspruch 1, wobei Mg(OH) 2, das im an L-Weinsäure und Magnesium-L-tartrat, die in den Verfahren der Schritte (ii) und (v) benötigt wird, al- Schritten(ii) bzw. (viii) verwendet werden, imBereich ternativ als Teil der integrierten Verfahren für die Ge- von 85 - 95 % (Molbasis) der Menge an K+ in der winnung von Pottaschesulfat aus Kainitmischsalz Schönit-Endflüssigkeit liegen. 15 erzeugt werden kann.

6. Verfahren nach Anspruch 1, wobei in Schritt (ii) Mee- 16. Verfahren nach Anspruch 1, wobei Calciumcarbo- resalgensaft von Kappaphycus alvarezi, der 3,0 - 4,5 nat, das im Verfahren von Schritt (vii) benötigt wird, Gew./Vol.-% Kaliumchlorid enthält, alternativ statt aus der integrierten Herstellung von Pottaschesulfat Schönit-Endflüssigkeit verwendet wird, um Kalium- 20 und Ammoniumsulfat aus Kainitmischsalz erhalten bitartrat mit ähnlicher Effizienz zu erhalten. werden kann.

7. Verfahren nach Anspruch 1, wobei in Schritt (ii) rest- 17. Verfahren nach Anspruch 1, wobei Kaliumsulfat, Ka- liche Mutterlauge aus der Meersalzgewinnung statt liumnitrat, Kaliumphosphat oder Kaliumcarbonat in Schönit-Endflüssigkeit verwendet wird, um Kalium- 25 Schritt (v) durch jeweiliges Verwenden von Magne- bitartrat zu erhalten. siumsulfat, Magnesiumnitrat, Magnesiumphosphat oder Magnesiumcarbonat statt MgCl2 erzeugt wer- 8. Verfahren nach Anspruch 7, wobei die Gewinnung den können. von Kalium-L-bitartrataus restlicherMutterlauge aus der Meersalzgewinnung, die 3,25 % Gew./Vol. KCl 30 18. Verfahren nach Anspruch 1, wobei die gesättigte Ka- aufweist, nur 54 - 58 % betrug, d.h. andere Bestand- liumchloridlösung Pottaschesulfat auf die Reaktion teile der Lösung können einen starken Einfluss auf mit Schönit hin erzeugt. die Gewinnung und Zusammensetzungen von SEF ausüben und Saft ist für die praktische Durchführung der Erfindung besser geeignet. 35 Revendications

9. Verfahren nach Anspruch 1 und 2, wobei die Gewin- 1. Procédé sûr et efficace d’extraction pour la récupé- nung von Kaliumbitartrat 85 - 95 % auf molarer Basis ration d’une solution quasi-saturée de chlorure de mit Bezug auf L-Weinsäure und Magnesium-L-tart- potassium, exempte d’impuretés où ledit procédé rat, die in den Schritten (ii) bzw. (viii) verwendet wur- 40 comprend les étapes de : den, betrug. i. fourniture d’une liqueur finale de schoenite 10. Verfahren nach Anspruch 1, wobei die Gewinnung (SEL) contenant 4,0 à 5,5 % en pds/vol de K+ von Magnesiumtartrat mit Bezug auf Kaliumbitartrat obtenue à partir de la décomposition d’un sel 85 - 95 % in Schritt (v) betrug. 45 mixte de kaïnite en schoenite ; ii. traitement de la liqueur finale de schoenite 11. Verfahren nach Anspruch 1 und 2, wobei die Wasch- contenant 4,0 à 5,5 % en pds/vol de + Ktelle flüssigkeit von Magnesiumtartrat 7 - 9 % KCl im Falle qu’obtenue dans l’étape (i) avec une quantité von L-Weinsäure und 14 - 16 % beim DL-Isomer von sous-stoechiométrique d’acide tartarique à moi- 50 Weinsäure enthielt, was auf ein effizientes Entwäs- tié neutralisé avec Mg(OH) 2, pour obtenir du bi- sern der Aufschlämmung nach der Reaktion von tartrate de potassium et de la liqueur finale de Schritt (v) hinweist. schoenite épuisée en potassium ; iii. Séparation et lavage du bi-tartrate de potas- 12. Verfahren nach Anspruch 1, wobei in Schritt (vii) der sium précipité tel qu’obtenu à l’étape (ii) avec Gehalt an restlicher Weinsäure auf 200 - 400 ppm 55 de l’eau ; reduziert ist. iv. addition des produits de lavage à la liqueur finale de schoenite épuisée en potassium ; 13. Verfahren nach Anspruch 1, wobei in Schritt (iv) nach v. traitement du bi-tartrate de potassium tel

9 17 EP 2 751 028 B1 18

qu’obtenu à l’étape (iii) avec une quantité stoe- pds/vol de chlorure de potassium est utilisé de ma- chiométrique de MgCl 2 et Mg(OH)2 pour le con- nière alternative à la place de la liqueur finale de vertir en tartrate de magnésium tout en libérant schoenite pour obtenir du bi-tartrate de potassium le potassium dans la solution sous la forme de avec une efficacité semblable. chlorure de potassium quasi-saturé ; 5 vi. lavage du tartrate de magnésium tel qu’ob- 7. Procédé tel que revendiqué selon la revendication tenu à l’étape (v) et conservation séparée des 1, où dans l’étape (ii), des eaux-mères sont utilisées produits de lavage ; à la place de la liqueur finale de schoenite pour ob- vii. traitement de la liqueur finale de schoenite tenir du bi-tartrate de potassium. épuisée en K telle qu’obtenue à l’étape (iv) et 10 de la solution de chlorure de potassium obtenue 8. Procédé tel que revendiqué selon la revendication à l’étape (v) avec du carbonate de calcium et du 7, où la récupération du L-bi-tartrate de potassium chlorure de calcium pour précipiter l’acide tarta- des eaux-mères ayant 3,25 % en pds/vol de KCl était rique résiduel sous la forme de tartrate de cal- uniquement de 54 à 58 %, c’est-à-dire que d’autres cium insoluble ; 15 constituants dans la solution peuvent avoir une pro- viii. addition du tartrate de magnésium de l’étape fonde influence sur la récupération et les composi- (v) à un lot frais de liqueur finale de schoenite tions de SEL et de jus conviennent mieux à la prati- SEL conjointement à une quantité stoechiomé- que de l’invention. trique de HCl aqueux pour une fois à nouveau précipiter le bi-tartrate de potassium ; 20 9. Procédé tel que revendiqué selon les revendications ix. addition du bi-tartrate de potassium de l’étape 1 et 2, où la récupération du bi-tartrate de potassium (viii) aux produits de lavage de l’étape (vi) et était de 85 à 95 % sur une base molaire par rapport d’une quantité supplémentaire d’eau telle que à l’acide L-tartarique et au L-tartrate de magnésium requise suite au traitement avec des quantités respectivement utilisés dans les étapes (ii) et (viii). 25 stoechiométriques de MgCl2 et Mg(OH)2 pour une fois à nouveau précipiter le tartrate de ma- 10. Procédé tel que revendiqué selon la revendication gnésium et obtenir une fois à nouveau une so- 1, où la récupération du tartrate de magnésium par lution quasi-saturée de chlorure de potassium rapport au bi-tartrate de potassium était de 85 à 95 KCl suivie de la régénération de l’acide tartari- % dans l’étape (v). que à partir du tartrate de calcium obtenu à l’éta- 30 pe (vii). 11. Procédé tel que revendiqué selon les revendications 1 et 2, où le produit de lavage du tartrate de magné- 2. Procédé tel que revendiqué selon la revendication sium contenait 7 à 9 % de KCl dans le cas de l’acide 1, oùdans l’étape (ii)l’acide tartarique se trouvesous L-tartarique et 14 à 16 % d’isomère DL de l’acide une forme racémique ou optiquement active et de 35 tartarique, indiquant une déshydratation plus effica- préférence sous la forme de l’isomère L. ce de la suspension après la réaction de l’étape (v).

3. Procédé tel que revendiqué selon la revendication 12. Procédé tel que revendiqué selon la revendication 1, oùdans l’étape (ii)l’acide tartarique se trouvesous 1, où dans l’étape (vii) la teneur résiduelle en acide une forme pure ou sous une forme de sel. 40 tartarique est réduite à 200 à 400 ppm.

4. Procédé tel que revendiqué selon la revendication 13. Procédé tel que revendiqué selon la revendication 1, où dans l’étape (ii), la liqueur finale de schoenite 1, où dans l’étape (iv) les eaux-mères finales obte- contenant 4,0 à 5,5 % en pds/vol de K+ est traitée nues après la récupération du sel mixte de kaïnite 45 avec une quantité sous-stoechiométrique d’acide sont utilisées à la place du MgCl 2 pur. tartarique à moitié neutralisé avec du Mg(OH)2, à une température située dans la plage de 20 à 35 °C. 14. Procédé tel que revendiqué selon la revendication

1, où le HCl et le MgO/Mg(OH) 2 requis dans les éta- 5. Procédé tel que revendiqué selon les revendications pes (ii), (v) et (viii) peuvent être produits à partir de 50 1 et 2, où les quantités d’acide L-tartarique et de L- MgCl2 en utilisant les procédés connus décrits dans tartrate de magnésium utilisés respectivement dans l’art antérieur. les étapes (ii) et (viii), se trouvent dans la plage de 85 à 95 % (sur une base molaire) de la quantité de 15. Procédé tel que revendiqué selon la revendication + K dans la liqueur finale de schoenite. 1, où le Mg(OH) 2 requis dans le procédé des étapes 55 (ii) et (v) peut être alternativement généré en tant 6. Procédé tel que revendiqué selon la revendication que partie des procédés intégrés pour le sulfate de 1, où dans l’étape (ii), du jus d’algue provenant de la récupération de potasse à partir de sel mixte de Kappaphycus alvarezi contenant 3,0 à 4,5 % en kaïnite.

10 19 EP 2 751 028 B1 20

16. Procédé tel que revendiqué selon la revendication 1, où le carbonate de calcium requis dans le procédé de l’étape (vii) peut être obtenu à partir de la produc- tion intégréedu sulfate depotasse et du sulfate d’am- monium à partir de sel mixte de kaïnite. 5

17. Procédé tel que revendiqué selon la revendication 1, où le sulfate de potassium, le nitrate de potassium, le phosphate de potassium ou le carbonate de po- tassium sont générés dans l’étape (v) en utilisant 10 respectivement du sulfate de magnésium, nitrate de magnésium, phosphate de magnésium ou carbona- te de magnésium à la place de MgCh.

18. Procédé tel que revendiqué selon la revendication 15 1, où la solution saturée de chlorure de potassium produit du sulfate de potasse par réaction avec la schoenite.

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• US 7041268 B, Ghosh P. K. [0003] [0006] • US 957295 A, Alberti A. [0009] • US 2617710 A, Kielland J. [0005] • US 2710789 A, Boeri G. [0009] • WO 2007054953 A [0006] • US 3069230 A, Pescarolo B. [0010] • US 8182784 B, Paul P. [0006]

Non-patent literature cited in the description

• SHUKLA, B. K. Adaptation of the bitartrate method for the estimation of potassium in sea bittern, ht- tp://www.csircentral.net/in- dex.php/record/view/88029 [0012]

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