Use of Clays Materials from Northern Côte d’Ivoire for the Adsorption of Thymol Blue in Aqueous Solution

Water contamination by dyes and related organic substances creates a need for effective treatment methods. This study investigated the adsorption of thymol blue from aqueous solution by clay materials collected from Bondoukou (BON) and Korhogo (KOR) in northern Côte d’Ivoire. Natural clay fractions and fractions saturated with sodium or calcium ions were characterised using mineralogical, chemical and textural analyses. Batch experiments examined contact time, adsorbent mass, solution pH, temperature and initial dye concentration. The raw BON and KOR clays had specific surface areas of 41.35 and 40.45 m²/g, respectively, and kaolinite was their dominant mineral phase. Thymol blue adsorption increased rapidly during the first 30 minutes and approached equilibrium after approximately 40 minutes. At 40 minutes, adsorption efficiencies ranged from 57.42% for untreated BON to 80.11% for calcium-saturated KOR. The highest efficiencies were observed at pH 2, with lower adsorption at higher pH values. Adsorption generally increased with clay mass and initial dye concentration, while calcium-saturated clays performed better than the corresponding untreated and sodium-saturated materials. The pseudo-second-order model described the kinetic data more closely than the pseudo-first-order model, with coefficients of determination ranging from 0.996 to 0.999. The reported thermodynamic parameters were consistent with spontaneous, endothermic adsorption. These findings indicate that the studied clays warrant further evaluation as adsorbents for thymol blue in contaminated aqueous media.