Valorization of Green Clay from Bouaflé (Ivory Coast) in the Simultaneous Elimination of Organic Pollutants and Metallic Trace Elements by Adsorption: Case of Methylene Blue and Cadmium Ions

Abstract

The objective of this work was to valorize the clays of Côte d'Ivoire in the treatment of wastewater. The study focused on the ability of raw clays from Bouaflé city to adsorb methylene blue and cadmium ions, in aqueous solution. The physicochemical characteristics of the clay were determined using the measurement of its specific surface area, chemical analysis and mineralogical analysis. It emerges from these characterizations that clay is essentially composed of type 2/1 minerals such as illite (32.94%), type 1/1 kaolinite (8.47%), quartz (40.23 %) and approximately iron oxy-hydroxides (18.36%). Its specific surface is 37.58 m2 / g. The kinetics, thermodynamics and isotherms of adsorption have been used to understand the mechanism of adsorption. The results obtained show that the organic pollutant alone in solution (methylene blue (MB)) is adsorbed quite quickly. We obtained a decoloration yield greater than 90% after 40 min of adsorbate-adsorbent contact. The elimination of methylene blue is greater in a basic medium. The BM adsorption kinetics were modeled. The comparison of the correlation factors of the different kinetic models used has shown that the adsorption kinetics of the organic pollutant (MB) better match the pseudo second order kinetic model. Thermodynamics predicted a spontaneous endothermic surface reaction, due to the positive sign of  and the negative sign of , obtained (  = 31.398;  = -12.635). Analysis of adsorption isotherms allowed us to show that the adsorption of methylene blue on clay is physisorption type and in monolayer. The experiments were also performed with an aqueous solution containing both methylene blue and cadmium ions. After a contact time of 120 min, 60% of the cadmium ions are adsorbed on the clay against only 20% of methylene blue. Thus, clay preferentially eliminates trace metal elements (Cd2+) compared to organic pollutants (methylene blue).