Extraction of phosphoric acid

Modem commercial wet-acid purification processes (see Fig. 4) are based on solvents such as C to Cg alcohols, ethers, ketones, amines, and phosphate esters (10—12). Organic-phase extraction of phosphoric acid is accompHshed in one or more extraction columns or, less frequently, in a series of countercurrent mixer—settlers. Generally, 60—75% of the feed acid P2 s content is extracted into the organic phase as H PO. The residual phosphoric acid phase (raffinate), containing 25—40% of the original P2O5 value, is typically used for fertilizer manufacture such as triple superphosphate. For this reason, wet-acid purification units are almost always located within or next to fertilizer complexes. 

The green phosphoric acid from a phosphoric acid plant (PAP) contains 25-30% H3PO4. The acid is heavily entrained with impurity cations, among which arsenic, cadmium, and uranium are the most toxic. In addition, anions, like chloride, fluoride, and sulfate must be considered. Selective extraction of phosphoric acid [18] as an adduct complex with TBP according to the block diagram in Fig. 14.12 has been used to produce acid of food grade. 

Ann. Chim., 1791, xi, 143 a ref. to Bemiard, Obs. Phys., 1789, xvi, as having found this is incorrect two papers by him there deal only with the extraction of phosphoric acid from egg-shells (p. 150) and the Wieliczka salt mines (p. 459). 

Although usually handled as an aqueous solution, formaldehyde cyanohydrin can be isolated in the anhydrous form by ether extraction, followed by drying and vacuum distillation (23). Pure formaldehyde cyanohydrin tends to be unstable especially at high pH. Small amounts of phosphoric acid or monochloroacetic acid are usually added as a stabiLher. Monochloroacetic acid is especially suited to this purpose because it codistiHs with formaldehyde cyanohydrin (24). Properly purified formaldehyde cyanohydrin has excellent stability (25). 

Ferrocene (46.4 g., 0.250 mole) (Note 1) is added to a well-stirred solution of 43.2 g. (0.422 mole) of bis(dimethylamino)-methane (Note 2) and 43.2 g. of phosphoric acid in 400 ml. of acetic acid in a 2-1. three-necked round-bottomed flask equipped with a condenser, a nitrogen inlet, and a mechanical stirrer (Note 3). The resulting suspension is heated on a steam bath under a slow stream of nitrogen (Note 4) for 5 hours (Note 5). The reaction mixture, a dark-amber solution, is allowed to cool to room temperature and is diluted with 550 ml. of water. The unreacted ferrocene is removed by extracting the solution with three 325-ml. jiortions of ether. The aqueous solution is then looled in ice water and made alkaline by the addition of 245 g. 

Note The derivatized steroids can be extracted from the blue chromatogram zones with alcohol and quantitatively determined by means of the Zimmermann reaction, which is not interfered with by the presence of phosphoric acid and phosphomolybdic acid. A yellow background can be bleached by exposure to anunonia vapor [2]. 

Y. B. Zeng and S. B. Fu. The inhibiting property of phosphoric acid esters of rice bran extract for barium sulfate scaling. Oilfield Chem, 15(4) 333-335,365, December 1998. 

Transfer the residue prepared as in Section 6.1.1 into a 300-nL separatory funnel with 25 mL of phosphate buffer solution (0.1 M, pH 7.4). Add 10 mL of saturated aqueous sodium chloride and 50 mL of 0.5 M sodium hydrogen carbonate to the funnel and shake the funnel vigorously for 1 min. Add 70 mL of ethyl acetate to wash the aqueous layer to the funnel, shake, separate, and discard the ethyl acetate layer. Repeat this extraction procedure three times. Add 2 mL of phosphoric acid and 20 mL of an acetate buffer solution (0.1 M, pH 4) to the aqueous layer and extract the mixmre with 50 mL of ethyl acetate three times. Combine the extracts and filter into a 500-mL round-bottom flask through 60 g of anhydrous sodium sulfate supported by a plug of cotton wool in a funnel. Concentrate the filtrate to dryness under reduced pressure. 

The regioselectivity of a Rhodococcus rhodochrous nitrilase has been demonstrated for the conversion of 5-fluoro-l,3-dicyanobenzene to 5-fluoro-3-cyano-benzoic acid [62]. The nitrilase was expressed in an Escherichia coli transformant, and a cell-free extract was employed as catalyst (0.14wt% cell-free extract) in 0.1m sodium phosphate buffer (pH 7.2) at 25 °C containing 0.18 m 5-fluoro-l,3-dicyanobenzene. After 72 h, the conversion was >98% and the reaction was stopped by addition of phosphoric acid (pH 2.4) to yield 5-fluoro-3-cyano-benzoic acid as a crystalline product (97% isolated yield). 

Alkyl esters of phosphoric acid and phosphine oxides will extract metals and mineral acids by direct solvation. Tri-//-butyl phosphate (TBP) and tri- -octyl phosphine oxide (TOPO)... 

Various processes have been used for uranium extraction from phosphoric acid solution their main features are listed in Table 12.4. The HDEHP-TOPO process is increasingly preferred over others because of the stability of the extractant and the well-understood chemistry of the process. 

A mixture of 118 g. (1 mole) of succinic acid, 188 g. (2 moles) of phenol, and 138 g. (83 ml., 0.9 mole) of phosphorus oxychloride (Note 1) is placed in a 2-1. round-bottomed flask fitted with an efficient reflux condenser capped with a calcium chloride tube (Notes 2 and 3). The mixture is heated on a steam bath in a hood (Note 3) for 1.25 hours, 500 ml. of benzene is added, and the refluxing is continued for an additional hour. The hot benzene solution is decanted from the red syrupy residue of phosphoric acid and filtered by gravity into a 1-1. Erlenmeyer flask. The syrupy residue is extracted with two 100-ml. portions of hot benzene, which are also filtered into the Erlenmeyer flask. The combined benzene solutions are concentrated to a volume of about 600 ml. (Note 4), and the pale yellow solution is allowed to cool, whereupon the diphenyl succinate separates as colorless crystals. It is filtered with suction on a Buchner funnel, washed with three 50-ml. portions of ether, and dried on a porous plate at 40°. The yield of diphenyl succinate, m.p. 120-121°, is 167— 181 g. (62-67%) (Note 5). 

After the discovery of phosphoric acid in the hones of the vertabrata, the old methods of extracting phosphorus from urine were totally abandoned, and it is now obtained almost exclusively from bones, Phosphoric acid exists In bones In the annexed form —... 

To 68 g. (0.5 mole) of phenylacetic acid (Org. Syn. 2, 63) (Note 1) in a i-l. flask fitted with a reflux condenser and a system for absorbing hydrogen chloride (Org. Syn. 8, 27) (Note 2), is added 35 g. (0.25 mole) of phosphorus trichloride. The mixture is heated on a steam bath for one hour. While the contents of the flask are still warm, 400 cc. of dry benzene is added. The benzene solution of phenylacetyl chloride is decanted from the residue of phosphorous acid on 75 g. (0.56 mole) of anhydrous aluminum chloride in a dry, i-l. flask which can be fitted to the same condenser. The reaction is vigorous at first and cooling is necessary. The mixture is refluxed for one hour on a steam bath, then cooled and poured into a mixture of 500 g. of cracked ice and 200 g. of concentrated hydrochloric acid. The benzene layer is separated, and the aqueous layer is extracted once with a mixture of 100 cc. of benzene and 100 cc. of ether (Note 2). The ether-benzene solution is washed once with 100 cc. of water (Note 3), and then dried over 40-50 g. of calcium chloride. The solution is filtered (Note 4) with suction into a i-l. Claiscn flask and the solvent is removed by distillation under reduced pressure (Note 5) the residue consists of a brown oil which solidifies on cooling. 

The previous assay was applied to the analysis of SDZ in salmon tissue, with some modifications. The re-extraction with phosphoric acid solution was replaced by SPE on an SCX cartridge preconditioned with MeCN and phosphoric acid solution. The cartridge was washed with MeCN, and SDZ was eluted with an MeCN phosphoric acid mixture. The eluate was injected directly into the chromatographic system, followed by postcolumn derivatization under similar conditions to the previous assay. The derivatization time was 1.2 min, and the fluorescence intensity was approximately a quarter of that for optimal conditions. However, the postcolumn derivatization was found to be considerably less labor intensive and was easily reproducible (recoveries 83-85% CV < 7%). A significant improvement in the LOD value was obtained (0.2 yug/kg) (160). The SDZ residues from incurred salmon tissue were confirmed by MS detection however, the sample cleanup should be improved due to the lack of sensitivity of MS. Therefore, SDZ residues were eluted from the SCX SPE cartridge with phosphoric acid, and the eluate was concentrated on a C18 SPE cartridge preconditioned with MeOH and water. The residues were eluted with MeCN, and the eluate was evaporated to dryness and reconstituted prior to the analysis. The column effluent was delivered into the atmospheric-pressure ion source, and SIM was chosen for positive ions at m/z 251, 158, 156, and 108, respectively (161). 

The solvent extraction of rare-earth nitrates into solutions of TBP has been used commercially for the production of high-purity oxides of yttrium, lanthanum, praseodymium and neodymium from various mineral concentrates,39 as well as for the recovery of mixed rare-earth oxides as a byproduct in the manufacture of phosphoric acid from apatite ores.272 273 In both instances, extraction is carried out from concentrated nitrate solutions, and the loaded organic phases are stripped with water. The rare-earth metals are precipitated from the strip liquors in the form of hydroxides or oxalates, both of which can be calcined to the oxides. Since the distribution coefficients (D) for adjacent rare earths are closely similar, mixer—settler assemblies with 50 or more stages operated under conditions of total reflux are necessary to yield products of adequate purity.39... 

J. J. Berzelius prepared lead phosphate by adding a soln. of lead acetate to a nitric acid soln. of bone-ash, and decomposed the lead phosphate by treatment with dil. sulphuric acid, and removed the last traces of lead by hydrogen sulphide and W. Odling treated a soln. of sodium phosphate in ice-cold water with lead acetate, and decomposed the washed precipitate suspended in water with hydrogen sulphide. The soln., freed from the precipitated lead sulphide, was evaporated to remove the hydrogen sulphide. J. Persoz digested the soln. of bone-ash with ferric or aluminium oxide, decomposed the precipitated phosphate with sulphuric acid, and afterwards extracted with phosphoric acid with alcohol. L. Thompson precipitated the lime by treating the calcium phosphate with oxalic acid. W. H. Ross and co-workers purified phosphoric acid by a process of fractional crystallization. 

The former is deposited in yellow crystals, mixed with sulphur when acetoxime is treated with phosphorus pentasulphide in carbon bisulphide soln. the insoluble product extracted with alcohol and the alcoholic soln. heated to boiling the compound separates from cold water in large, transparent, seemingly monoclinic prisms, melts at 146° 150° with decomposition, and is readily soluble in water, but only sparingly in alcohol, and insoluble in ether and carbon bisulphide. It decomposes carbonates, gives a colourless precipitate with lead acetate, and is decomposed by hot dilute nitric acid with separation of sulphur and formation of phosphoric acid it is also decomposed by mercuric oxide, the filtrate from the precipitated mercury sulphide giving all the reactions of phosphoric acid. 

The so-called "trapped sites" of classical mobile-site, liquid ion exchanger electrodes belong to a category of compounds known as ion association extractants. Examples are long-chain diesters of phosphoric acid and tricaprylylmethylammonium (Aliquat) ions. The latter cation was studied extensively by Freiser and co-workers (1-3 ) in the design of anion sensors. 

Synergistic extraction, in the system DEHPA and TOPO, is quite interesting for its ability to extract uranium from high concentrations of phosphoric acid (38). This finds application in the recovery of uranium from dilute phosphoric acid medium in... 

There are various types of organic proton exchangers (34, 35, 38). Diesters of phosphoric acid, (RO)2P = 0(0H), phosphonic acids, R(RO)P = 0(0H), and phos-phinic acids, R2P = 0(0H), where R represents linear or branched alkyl or phenyl substituents, are the most common cation exchangers developed in liquid-liquid extraction for the extraction of trivalent 4/and 5/elements. They were initially developed for the American TALSPEAK and the Japanese DIDPA processes and have recently been introduced in the French DIAMEX-SANEX process. As for previously described NOPCs, these organophosphorus acids present oxygen-donor atoms (hard bases) in their structures and therefore will easily coordinate trivalent lanthanide and actinide cations, but they will not allow complete discrimination of the two families of elements. However, contrary to previously described neutral organophosphorus... 

As a consequence, the selectivity of extraction of first transition series dications does not follow the Irving Williams order when these reagents are used in base metal recovery. The bis(2-ethylhexyl)ester of phosphoric acid (D2EHPA) shows [1] a preference Zn2+ > Cr21 > Mn2+ > Fe2+ > Co2+ > Ni2+ V2+ which is exploited in the recovery of zinc from primary sources. [69] M2+ ions which form tetrahedral complexes and M3+ ions which show a preference for octahedral donor sets give neutral complexes with 4 1 and 6 1 D2EHPA metal stoichiometries respectively,... 

FIGURE 2 Solvent extraction process for purification of phosphoric acid. 

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