RECOVERY OF SOME TRACE ELEMENTS FROM IRAQI PHOSPHATE PRODUCTS

G. Jalhoom, Moayyed; S. Al-Bassam, Khaldoun; H. Humaidi, Abbas

	RECOVERY OF SOME TRACE ELEMENTS FROM IRAQI PHOSPHATE PRODUCTS
Iraqi Bulletin of Geology and Mining
Article 1, Volume 0, Issue 7, 2017, Pages 79-92
Authors
Moayyed G. Jalhoom; Khaldoun S. Al-Bassam; Abbas H. Humaidi
Abstract
Trials have been attempted to evaluate the recovery of some trace elements in the Iraqi phosphate rocks and phosphate fertilizers products since the nineties of the twentieth century. Leaching solid-liquid extraction was conducted for the recovery of Cd and Zn from the basic slime wastes produced in the Iraqi Al-Qaim fertilizer complex using various inorganic acids, basis and ammonium salts. Almost quantitative recovery was obtained for Cd and Zn by ammonium chloride and ammonium nitrate solutions. A method has been developed for the recovery of U, Th and other heavy elements from the acidic phosphogypsum produced as waste at Al-Qaim fertilizer complex using the concept of preferential solubility of phosphogypsum over other trace elements sulfates and phosphates in potable water. The undissolved or partially dissolved metal salts remain hanged as colloids then accumulated after 30 – 60 minutes. Most of the trace elements are expected to exist in water as sparingly or insoluble sulfates, phosphates, silicates and fluorides. Chemical analysis of the isolated phosphogypsum, after water evaporation, showed reasonable purity suitable for various industrial applications. The method has been further developed recently using pH, conductimetric and turbidometric techniques to follow the solubility of phosphogypsum as function of various parameters. Uranium, on the other hand, was recovered on industrial scale, from green phosphoric acid by liquid-liquid extraction technique and di-2-ethyl-hexyl-phosphoric acid (DEPA)-trioctylphosphene oxide (TOPO)-kerosene/ phosphoric acid solutions. The plant installed at Al-Qaim depends on mixer settlers as contactors. More than 150 tons of uranium was recovered as yellow cake, but the plant was destroyed during the 1991 war. High purity phosphoric acid was produced from green phosphoric acid on a pilot plant scale using liquid-liquid extraction technique and mixer-settler contactors. The extraction system "40% tributyl phosphate (TBP)-kerosene" was applied as the organic phase. The process revealed group removal of U, Th and other heavy metals as by-products in 20% green phosphoric acid.
Keywords
Phosphate industry; Phosphoric acid; Trace elements recovery; Slime; Phosphogypsum

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