The present work aims to study the affinity of a component of the thyme essential oil “thymol” to natural Moroccan clay “Rhassoul” using the adsorption technique. The physicochemical characterizations of the purified and modified clay were carried out by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), DTA/TGA, and SEM‐EDX. Thymol adsorption tests on the purified Rhassoul (Rh‐P) and the modified one by CTAB (Rh‐CTAB) were followed by UV‐visible spectroscopy. They show that the adsorption isotherms can be described by the Freundlich model and that the kinetics of adsorption is in accordance with the pseudo‐second‐order model for the two clays. Adsorption capacities obtained were of the order of 6 mg/g for the purified Rhassoul and 16 mg/g for the modified Rhassoul by cetyltrimethylammonium bromide (CTAB). These values show that the modified Rhassoul has a better adsorption capacity compared to the purified Rhassoul.