Coagulation-flocculation by aluminum sulfate of organic phenolic compounds and effect of calcium and magnesium salts
The objective of this study was to observe the effectiveness of coagulation-flocculation by aluminum sulfate on the removal of organic compounds with phenolic functional groups (phenol and pyrogallol). The work focused on the impact of the inorganic components of water hardness, calcium and magnesium, which are often present in the inorganic matrix of Algerian waters. Jar-test trials were conducted on the two phenolic compounds dissolved in distilled water only and then in water enriched with mineral salts. The tests were performed on synthetic solutions of distilled water enriched with calcium and magnesium ions, introduced in various forms (CaCl2•2H2O; CaSO4•2H2O; CaCO3; MgCl2•6H2O; MgSO4•7H2O). Several reaction parameters were varied, notably the pH and the salt content, and this approach yielded a better understanding of the mechanisms of interaction between phenolic compounds and calcium/magnesium salts. The obtained results indicate that the process efficiency depends on the number and position of phenolic groups on the organic molecules. The main mechanisms could be a physical adsorption, a ligand-exchange reaction or surface complexation on the aluminum hydroxide floc. The addition of inorganic salts appears to improve removal efficiencies for the tested phenolic compounds and affects the optimal pH range for coagulation. The application of this method to mineralized waters (well water), collected in the region of Biskra located in the southeastern Algeria, resulted in improvement of yields, compared to those obtained in distilled water.