Adsorption of organic matter from industrial phosphoric acid (H3PO4) onto activated bentonite

The Tunisian industrial phosphoric acid (IPA) was obtained from the phosphate rock by the wet process. However, the organic matter (OM) contained in the acid may interact with organic solvents to form stable foams, preventing phase settling, or simply by forming cross layers and organic phases, and denaturing part of the solvent. Hence, removal of these organics seems to be an important step for the production of decontaminated phosphoric acid. In the phosphoric acid plant of M'dhilla, the OM can be found as colloidal suspension and soluble forms. The colloidal organics are coagulated and deposited with the gypsum precipitation during the aging of H3PO4, while the soluble part remains behind. The purpose of this work was to study the OM adsorption onto montmorillonite bentonite. Equilibrium data are analyzed by the Langmuir, Freundlich and Redlich–Peterson adsorption isotherm models.