ESSAIS DE COAGULATION DE L’ACIDE PYROMELLITIQUE EN MILIEUX AQUEUX MINERALISES

Abstract

The objective of this study is to investigate the effectiveness of coagulation by aluminium sulphate on the removal of aromatic organic compounds and to demonstrate the stoichiometric laws of aluminium sulphate / organic matter. To try to establish correlations between the initial content of this organic compound and the dose of coagulant to be applied, the pyromellitic acid was dissolved at 1 to 20 mg / l of distilled water and several mineralized waters from Biskra region. For pHs close to neutrality, these aqueous solutions were coagulated by increasing aluminium sulphate dosage. The results obtained indicate that the efficiency of the process as well as the dosage of the coagulant depends on the pH and on the initial concentration of the organic compound but also on the ionic strength of the dilution water. The results also showed that the increasing total mineralization of water had an inhibitory effect on the elimination of pyromellitic acid. Depending on the pH and the total mineralization of the aqueous medium, several mechanisms may be suggested such as complexation with the soluble or insoluble aluminum forms or adsorption on the aluminum hydroxide flocs. Highlighting of a stoichiometry of the reactions showed that the laws linking the dosage of the coagulant to the initial concentration of the pyromellitic acid were highly dependent on the total quantity of mineral salts in the various waters tested.

Keywords

• Pyromellitic acid
• Coagulation
• Mineralization
• Mechanisms
• Stoichiometry