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

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℃ presents three straight segments attributed at the formation of the hemihydrate (CaSO4·1/2H2O:HH), the dihydrate (CaSO4·2H2O: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 (CaSO4:AH). Moreover, the variation of mass enthalpy versus temperature presents a break at the T = 45℃. 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℃.

DISSOLUTION KINETICS OF PHOSPHATE ORE IN ACIDIC SOLUTIONS

1 INTRODUCTIONIn the wet processes of industrial phosphoric acid production,sedimentary or francolitephosphate ore dissolves in mineral acid.If the acid is sulphuric acid,which is a classic wetprocess,the crystallization of calcium sulphate occurs.The rate of crystallization is normallyconsidered quite slower than that of dissolution.So only few publications have

Synthesis of Novel Dark Red Phosphate Pigments in Imitation of Natural Ore

As novel dark red pigment,sodium manganese phosphate,NaMnPO4,imitated with Natrophilite,was synthesized by heating at various conditions.The heating temperature and time,volume of water,phosphorus resource were studied in this process.The obtained powders were estimated with X-ray diffraction(XRD),Infrared(IR)spectra,ultraviolet-visible(UV-Vis)reflectance spectra,and L^*a^*b^*color space.Further,similar chemical compositions with NaMnPO4 were also studied in the same method.The obtained samples had weak peaks of NaMnPO4 in XRD patterns.Sample synthesized in Na/Mn=1/1 at 700℃for 6 hours indicated high redness,a^*value.

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

Mixture of phosphoric and sulfuric acid solutions has been used to investigate the dissolution of natural phosphates (PN) by DRC. The effect of concentration, particle size and stirring speed reaction is examined. Thermochimique properties of each kinetic parameters reaction are determined. It was found that these parameters have a considerable effect on the thermochemical aspect of the attack reaction. It is known that the process of PN sulphophosphoric acid attack leads to the formation of dihydrate (CaSO4.2H2O: DH). The present work shows the precipitation of other residues their formula depends on factors studied. The increase in concentration leads to the formation of hemihydrate (CaSO4v1/2H2O:HH) beside DH for the low values of% H2SO4 due to the solubility of dihydrate on the etching solution and the precipitation of (Ca (H2PO4)2.2H2O) next of DH for low agitation values because of the lack of turbulence between the liquid phase and the solid phase which favors the precipitation of this latter compound.

Preparation of Novel Scorzalite Imitated Phosphate Pigments

Novel phosphate pigments imitated with Scorzalite,FeAl2(PO4)2(OH)2,were prepared from iron and aluminum nitrate solutions,ascorbic acid,and phosphoric acid with pH adjustments(pH 5,7,9).The obtained precipitates were heated at 300,500,and 700°C for 1 h.The precipitates and their thermal products were estimated with X-ray diffraction(XRD),Infrared(IR)spectra,ultraviolet-visible(UV-Vis)reflectance spectra,and L*a*b*color space.The precipitated sample was not clearly colored,but it turned orange to red when heated.Samples prepared at low pH showed higher whiteness than samples prepared at high pH.The theoretical amount of ascorbic acid was sufficient to completely reduce iron during the adjustment.This study showed the possibility of novel inorganic phosphate red pigment.

Rare earth extraction from wet process phosphoric acid by emulsion liquid membrane

The recovery of rare earths （RE） during the wet processing of phosphoric acid is very important, the method of emul- sion liquid membrane （ELM） with di（2-ethylhexly） phosphate （D2EHPA） as carrier has the high selectivity while cannot provide a satisfactory extraction rate. Here novel method of emulsion liquid membrane （ELM） using Aniline as carrier to extract RE from the feed solution was proposed. The method could increase the extraction rate of RE in the real sample to 93%. The effects of dif- ferent parameters such as type and concentration of carrier and surfactant, hydrochloric acid concentration, organic to internal phase volume ratio, membrane to external phase volume ratio on extraction of RE3＋ were investigated. Quantitative extraction （〉93%） of RE3＋ was observed with 6 vol.% Aniline and 4 vol.% T 154 liquid membrane at external to internal phase volume ratio of 10 for the feed solution. The proposed method of ELM using Aniline as carrier can be expected to provide a practical, efficient, and economical method for extracting RE from phosphate leach solution with high acidity in the industry of wet process phosphoric acid.