Wet process phosphoric acid purification by solvent extraction using N‐octanol and tributylphosphate mixtures

Abstract

BACKGROUND: Solvent extraction using organic extractants is an important technology for purifying wet process phosphoric acid. The purification of the wet process phosphoric acid by liquid-liquid extraction using solvent mixtures of N-octanol and tributylphosphate has been investigated. RESULTS:The purification process comprised extraction, scrubbing and stripping operations. The extraction conditions, i.e. shaking time, temperature, composition of solvent mixtures and P 2 O 5 concentration for purification of the wet process phosphoric acid were studied. The phase diagram of the pseudo-ternary system H 3 PO 4 -H 2 O-solvent mixtures at 313.15 K was determined. The McCabe-Thiele diagram showed that three counter-current stages achieved about 91 wt% P 2 O 5 extraction at 313.15 K. Scrubbing and stripping operations using pure phosphoric acid with 10 wt% P 2 O 5 and doubly distilled water, respectively, were studied. CONCLUSIONS: The phosphoric acid finally produced was found to be high grade which met the special requirements of the user. Optimization of the extraction conditions and system was capable of providing academic and technical foundations to realize industrial production.

Purification of Wet Process Phosphoric Acid by Solvent Extraction using Cyclohexanol

“…The water content in the organic phase was determined by the Karl-Fisher potentiometric titration method using a compact potentiometric titrator (Metrohm 916 Ti-Touch, Switzerland) [11]. Measurement of Fe 3+ concentration in the aqueous solution was performed using a UV-Visible spectrophotometer (Mapada UV-1100, China) at a wavelength of 510 nm [17].…”

“…Many organic solvents have been investigated, e.g. esters [7][8], ethers [9], ketones [10] and alcohols [11]. Aliphatic alcohols, such as butanol, hexanol and octanol, have been studied as extractants diluted in kerosene for purification of WPA.…”

Separation of phosphoric acid and nitric acid mixtures with tri-n-butyl phosphate at 303.2K

“…It could be explained as electronic effects which acts directly on the interactions. H 3 PO 4 and HNO 3 molecules would form hydrogen bond with TBP molecules [5,7,15]. TBP could combine with H 3 PO 4 easily when the content of phosphoric acid is far more than that of nitric acid.…”

“…It has two methods to manufacture phosphoric acid. Commercially, phosphoric acid is produced by thermal and wet processes [4,5]. Though the impurity content is lower by using the thermal method, it consumes much more energy and incurs high production costs.…”

“…However, the wet process using phosphoric acid (WPA) contains many impurities beside solids and organic matters [7,8]. Many chemical techniques have been investigated for purifying WPA, e.g., precipitation, crystallization, ion exchange, electrodialysis and solvent extraction [3,5,[9][10][11].…”