Attack of Tunisian Phosphate Ore by a Mixture of Sulfuric and Phosphoric Acid: Thermochemical Study by Means of Differential Reaction Calorimetry

Abstract

A calorimetric, Differential Reaction Calorimetry (DRC), study of the thermochemical of the attack of a phosphate ore from Gafsa region (Tunisia) by a mixture of sulfuric and phosphoric acid is undertaken at different solid-liquid ratio and different temperature. The plot of the quantity of heat measured by integrating the raw signal as a function of the dissolved mass in the same volume solution at 25˚C presents three straight segments attributed at the formation of the hemihydrate (CaSO 4 •1/2H 2 O:HH), the dihydrate (CaSO 4 •2H 2 O:DH) or a mixture of these two products checked by X-ray diffraction, infrared spectroscopy and thermal analysis (Differential Scanning Calorimeter: DSC). The attack by the acid mixture was performed at higher temperature and showed in addition the formation of another form of calcium sulfate:anhydrous (CaSO 4 :AH). Moreover, the variation of mass enthalpy versus temperature presents a break at the T = 45˚C. According to our results, it seems that the effect of the temperature on the sulfo-phosphoric attack reaction on the natural phosphate (NP) generates a change of mechanism at around 45˚C.

Investigation of Sulfonium-Iodide-Based Ionic Liquids to Inhibit Corrosion of API 5L X52 Steel in Different Flow Regimes in Acid Medium

“…The bands at ∼1643 cm –1 correspond to iron oxide and the alkylsulfonium group too, while the band at 1736 cm –1 corresponds to the remaining H 2 SO 4 . 71 , 72 The O–H stretching bands from physisorbed molecular water can be observed at 3386 cm –1 , while the signals at 2957 and 2854 cm –1 belong to the C–H stretching signal of the inhibitor aliphatic group and Fe 3 O 4 . 73 , 74 The C–H scissoring of the alkyl chain signals appears at 1459 cm –1 .…”

Effect of Different Kinetic Factors on the Thermochemistry of Sulfophosphoric Attack Reaction of Natural Phosphate Tunisian by DRC

“…Therefore, several publications were conducted to studies the dissolution of phosphate synthetic [3]- [11] or natural [12]- [22] in aqueous acid solutions to clarify the kinetics and the process mechanism to improve the performance of phosphate attack. However, phosphate rocks decomposition by sulfuric acid remains the most widely used method and over 90% of the phosphoric acid produced worldwide is manufactured by digestion of phosphate rocks with sulfuric acid as an acidulant [21].…”