Conversion of Moroccan phosphogypsum waste into nano-calcium fluoride and sodium hydrogen sulfate monohydrate
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ORIGINAL ARTICLE
Conversion of Moroccan phosphogypsum waste into nano‑calcium fluoride and sodium hydrogen sulfate monohydrate Yassine Ennaciri1 · Mohammed Bettach1 · Hanan El Alaoui‑Belghiti1 Received: 9 October 2019 / Accepted: 20 July 2020 © Springer Japan KK, part of Springer Nature 2020
Abstract The phosphoric acid production in the world generates a large amount of phosphogypsum with the emission of toxic acid fluorine gas into the atmosphere, which forms a significant source of environmental contamination. In this work, a novel and a simple procedure allows converting phosphogypsum waste by using hydrofluoric acid and sodium fluoride into valuable products. The obtained results confirm well the efficiency of this procedure, which permits to synthesize at room temperature, the sodium hydrogen sulfate monohydrate and a relatively pure nano-calcium fluoride from the exact stoichiometric proportions of the phosphogypsum, hydrofluoric acid, and sodium fluoride. The total phosphogypsum conversion is achieved after reaction time equal to 1.5 h. Generally, this procedure offers not only a solution for reducing phosphogypsum waste but also permits to obtain valuable products, which interest several sectors of industry. Keywords Conversion · Phosphogypsum · Calcium fluoride · Sodium hydrogen sulfate monohydrate Abbreviations AHF Anhydrous hydrofluoric acid cc Concentered acid da Dilute acid FSA Hexafluosilicic acid H2SiF6 HF Hydrofluoric acid P Pump PA Phosphoric acid H3PO4 PG Phosphogypsum PR Phosphate rock rpm Rotation per minute S Constant stirring SA Sulfuric acid H2SO4 STF Silicon tetrafluoride SiF4 t Time reaction (h) T Temperature (°C) TC Temperature control WL Weight loss wt Weight
* Yassine Ennaciri [email protected] 1
Introduction The industry of phosphates and its derivatives represent a large place in the industrial structure of Morocco. It is considered of high importance at the economic and social levels. The principal task of this industry consists to extract the phosphate ores for the production of the phosphoric acid H3PO4 (PA) necessary for the fertilizers’ manufacture. According to the experts, the global request of PA and phosphate fertilizers heighten every year, this engenders the simultaneous increase of the phosphogypsum (PG) quantity besides the high fluorine level compound emission to the atmosphere. The wet process PA production from the digestion of phosphate rock (PR) by sulfuric acid H 2SO4 (SA) can be expressed by the following chemical reactions [1]: ) ( Ca3 PO4 2 + 3H2 SO4 + 6H2 O → 3CaSO4 ⋅ 2H2 O + 2H3 PO4
(1)
CaCO3 + H2 SO4 + H2 O → CaSO4 ⋅ 2H2 O + CO2
(2)
CaF2 + H2 SO4 + 2H2 O → CaSO4 ⋅ 2H2 O + 2HF.
(3)
As more simplified:
Department of Chemistry, Laboratory of Physical Chemistry of Materials (LPCM), Faculty of Sciences, Chouaib Doukkali University, El Jadida, Morocco
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Vol.:(0123456789)
Journal of Material Cycles and Waste Management
( ) Ca10 PO4 6 F2 + 10H2 SO4 + 20H2 O → 10CaSO4 ⋅ 2H2 O + 6H3 PO4 + 2HF.
(4)
During this pro
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