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

Olfa Lachkar-Zamouri,Faten Bennour,Ismail Khattech,Khemaies Brahim

doi:10.4236/ampc.2018.811029

Abstract

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.

Highlights

The production of phosphoric acid is based on the attack of natural phosphates by the mixture of phosphoric and sulfuric acid
In a previous work [22], we studied the effect of the solid/liquid ratio and the temperature on the thermodynamic aspect of the sulfophosphoric attack reaction of a natural phosphate using a SETARAM calorimeter by differential reaction calorimetry (DRC)
The experimental protocol followed to study the dissolution of the PN in the mixture of sulfuric and phosphoric acid solution can be described as follows: 100 g of the attacking solution, S, (20 g of concentrated sulfuric acid and 80 g of recycled phosphoric acid, 20% of P2O5) and a mass “m” of the PN in a sealed sample holder which prevents its contact with the attacking solution were placed in the measuring reactor

Summary

Introduction

The production of phosphoric acid is based on the attack of natural phosphates by the mixture of phosphoric and sulfuric acid These acids are introduced simultaneously or successively [1]. These phosphates from different sources are expected to behave differently in acidulation processes. Olanipekun et al [20] in the range of 60 ̊C - 90 ̊C showed that the diffusion through an ash (or product) layer is the controlling step, and the activation energy of the dissolution of Nigerian phosphorite in aqueous solutions of sulfuric acid was determined as 17.60 kJ∙mol−1. A similar conclusion has been obtained for the Nigerian phosphorite in a mixture of sulfuric and hydrochloric acids with activation energy as 13.25 kJ∙mol−1 [19]

Methods

Results

Conclusion