Characterization of crude and calcined phosphates of Kef Essennoun (Djebel Onk, Algeria)
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Characterization of crude and calcined phosphates of Kef Essennoun (Djebel Onk, Algeria) L. Bounemia1 · A. Mellah1 Received: 6 August 2019 / Accepted: 4 August 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Rock phosphate is the fundamental component for the manufacture of phosphoric acid and phosphate fertilizers. The aim of this study is to predict how sample preparation of Kef Essennoun phosphate responds to heat treatment and to estimate the purity of the raw and calcined phosphates. The influence of temperature (600–900 °C) was evaluated. The evolution of thermal treatment and the characterization of the Kef Essennoun ore (Djebel Onk mine, Algeria) were carried out by various analytical techniques including X-ray diffraction (XRD), wavelength-dispersive X-ray fluorescence, Fourier-transform infrared spectroscopy, thermogravimetric analysis/differential thermal analysis, and scanning electron microscopy (SEM). The results showed that the raw phosphate is a mixture of six phases, of which carbonate hydroxyapatite [Ca10(PO4)3(CO3)3(OH)2] is the dominant phase. With heat treatment, at 700 °C, a fluorapatite [Ca5(PO4)3F] phase appeared, as confirmed by XRD analysis, with good crystallization indicated by SEM. The P 2O5 content was increased from 28.389% in raw phosphate to 31.085% in the calcined product. The dissolution of the calcined phosphate at 900 °C was completed by HNO3 acid attack, and occurred rapidly at ambient temperature. The results show that the production of phosphoric acid by C a5(PO4)3F was more easily achieved with optimized consumption of the acid attack. Keywords Phosphates · Phosphoric acid · Environment · Calcination · Characterization · Thermogravimetry
Introduction The Djebel Onk deposit in Algeria is a significant phosphate reserve. Djebel Onk is located approximately 100 km southwest of Tébessa, near the Tunisian border, with a capacity of about 2 billion tons of 53–61% tri-calcium phosphate (TPL) [1]. The current annual production is about 2.3–2.5 million tons of high-grade ore (25–26% P2O5). Organic matter is usually present in the phosphates in very small quantities, from 0.25 to 1%. Despite this low content, it hinders the purification of phosphoric acid. The main constituents of the organic matter in phosphate sediments include aliphatic and polynuclear aromatic hydrocarbon, lipids, fatty acids and humic compounds [2, 3]. The presence of organic matter in the phosphates is a major drawback because of the formation of foam that causes difficulties in separating phosphoric * L. Bounemia [email protected] 1
Commissariat à l’Énergie Atomique, Nuclear Research Centre of Algiers (CRNA), BP 399, 02 Bd Frantz. Fanon, Algiers, Algeria
acid and calcium sulfate [4, 5], and it hinders the recovery of uranium. Among the processes proposed in the literature, the calcination process has very interesting advantages in terms of eliminating organic matter and also decomposing the gangue minerals (carbonate) to form CaO and MgO, which can be separated after calcination by ex
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