Abstract
A kinetic study of dissolution of Tunisian natural phosphate or francolite whose particles have a mesoporous texture inindustrial phosphoric acid is carried out. Therefore, We focused on the study of the influence of certain parameters thatare close to those used in plants producing phosphoric acid which are the stirring speed (300, 500 and 700 rounds perminute), concentration of phosphoric anhydride (25, 30 and 35 percent of P2O5), and the temperature (60, 70 and 80degrees Celsius); we note that the rate of dissolution of this phosphate rises by increasing the precedent parameters.Because of the complexity of the study of the dissolution of phosphate in mineral acids. Several different published kineticmodels giving different expressions of speed versus time. The shrinking core model is the appropriate model used in ourwork in a solution where there is no calcium sulfate to calculate the rate constant k and the activation energy Ea = 3.3946Kcal/mol of this phosphate.
Highlights
Tunisia is conquering to the international scale in the field of production of phosphate rock or francolite and is considered among the top four producing countries in the world
We studied the influence of this parameter on the dissolution kinetics of phosphate
By varying the stirring speed to values 300, 500 and 700 rpm, we observe from the curves that the dissolution rate increases with the increasing of the stirring speed; in addition we note that the speed attack is very fast in the first two minutes and it gradually decreases
Summary
Tunisia is conquering to the international scale in the field of production of phosphate rock or francolite and is considered among the top four producing countries in the world. In the basin of Gafsa-Tunisia, the most common ore has a sedimentary origin which is the carbonated fluorapatite (or francolite) of general formula [1]: Ca10-n/2[PO4]6n(CO3)n(F,OH)2H2O. The carbonate fluorapatite has a crypto-crystalline structure in all Tunisian deposits. The crystal lattice of the apatite is the seat of several substitutions [2], the Ca ion can be substituted by Mg, Na, and in some rarer cases by Cd. Fertilizers provide nutrients for plants to enable optimal growth. Phosphate fertilizers are obtained from the processing of phosphate rock extracted from the ground. They are increasingly produced in the ore-producing countries [3]
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