Study of the Influence of Some Ions on the Adsorption of Phosphates by Clay Materials from Côte d’Ivoire

The eutrophication of water bodies resulting from discharges of industrial and domestic wastewater constitutes a major environmental problem. Indeed, eutrophication of aquatic environments, marked by the uncontrolled presence of aquatic plants on water bobies, has significant impacts on the properties of water, health of humans and fish, socio-economic activities, etc. To solve this environmental problem, several studies have revealed that eutrophication of aquatic environments can be treated by acting mainly on phosphorus, which is considered a limiting factor. Thus, the objective of this work is to study the removal of phosphates by adsorption on various clay materials, while examining the influence of the various ions contained in phosphorus environment. The clays studied were taken from several localities in Côte d’Ivoire. The clay fractions which were used for the tests were collected by sedimentation then chemically treated with Na+ and Mg2+ cations. These modified clays were brought into contact with synthetic phosphate solutions containing increasing quantities of H3O+, OH-; Na+, Mg2+, Cu2+ and Zn2+ ions. The results revealed that the presence of H3O+, Na+, Mg2+ and Zn2+ ions in solution facilitates the adsorption of phosphates. As for copper II ions (Cu2+), when their content is lower than the maximum accepted standard (7.874 μmol/L), adsorption of phosphates is favorable. However, beyond this value and in a basic environment, adsorption of phosphates by clays seems to be unfavorable. Thus, beyond water depollution, this study contributes to obtaining clays rich in phosphorus which could be used as agricultural fertilizers.