Uranium, recovery from wet process phosphoric acid

Uranium Recovery from Wet Process Phosphoric Acid... 

Inoue, K. and Nakashio, F., Technology of Uranium recovery from wet-process phosphoric acid (in Japanese). Kemikaru Enjiniaringu 27 (1982) 59-65. 

FIGURE 19.4-4 Comparison belwnen the LM and SX procemes Tor uranium recovery from wet process phosphoric acid. Redrawn from data in Hayworth el al. 

The O or S atoms in P=0 and P=S groups may act as electron donors although these groups form relatively weak complexes with electron acceptor compounds such as nonpolarizable, more electropositive (ie, hard) acids, including protons (14). Use is made of this property in the recovery of uranium from wet-process phosphoric acid by extractants such as trioctylphosphine oxide [78-50-2] and di(2-ethylhexyl) hydrogen phosphate [298-07-7]. 

Hurst, F. J. Recovery of uranium from wet-process phosphoric acid by solvent extraction, presented at Annual AIME Meeting, Las Vegas, February 1976. Young, W. Davy Power-Gas, Paper at AIME Annal Meeting, New Orleans, February 1979, p. 59. 

Hurst, F.J. and Crouse, D.J., Recovery of uranium from wet-process phosphoric acid by extraction with octylphenylphosphoric acid. Ind. Eng. Chem. Proc. Des. Dev., 1974, 13 286-291. 

There are a number of practical synergistic systems that make use of organophosphorus compounds. A classic example is the combination of HDEHP and TOPO. The TOPO is thought to replace water or HDEHP in the coordination sphere of the metal. Some early work in this area included a study of the extraction of uranium in such systems (82). Commercial processes now exist for the recovery of uranium from wet-process phosphoric acid utilizing synergistic systems (83,84). Descriptive studies of such systems have also been made (85,86). 

J>) reported on the application of emulsion liquid membrane technology to the recovery of uranium from wet process phosphoric acid. 

In 1908, it was discovered that samples of phosphate rock were many times more radioactive than the average rock sample taken from the earth s crust. It is now known that most apatitic rock contains 0.01—0.03 uranium, and its direct recovery from the phosphate mineral, or from wet process phosphoric acid, has been a subject of intense study for more than 30 years [14]. Most of the uranium in the earth s crust is believed to be associated with apatite. 

An especially intriraing use of liquid-membrane technology, reported for the first time recently by Fox and Hayworth et al.," is the recovery of uranium from wet process phosphoric acid (WPPA). In the manufacture of fertilizer fiom phosphate rock, the acid is solubilized by treatment with sulfuric acid. In addition to HjP04, this crude leachate can contain up to 0.18 g/L of uranium. Under oxidizing conditions this occurs as the uranate ion, UO . Solvent extraction (SX) processes have been developed to recover die uranium values. One of the most common of these uses a mixture of di-(2-ethylhexyl) phosphoric acid (D2EHPA) and trioctylpbosphine oxide (TOPO) in kerosene solution. The chemistry of solvent extraction is as follows ... 

The ELM process has been used extensively to extract organics from aqueous feed, e.g., phenol from water (13-15), in hydrometallurgical separations, like zinc from waste water (16-18) and uranium from wet process phosphoric acid (19,20), and in the recovery of rare earth metals (23,24),... 

Uranium recovery from the wet process phosphoric acid filtrate has been of interest for many years [47]. U.S. operations have recovered a total of 200,000 kg/yr of U3O8 (yellow cake) from this source [48]. Prior cleanup of dissolved organics in the raw phosphoric acid with activated carbon improves the ease of uranium extraction by providing clean phase separation. Eraction-ation of the natural radioactivity present in wet process acid has been examined [49]. 

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