The adsorption of psychoactive drugs (PADs) onto sodium-exchanged montmorillonite (Na-Mt) was investigated under two pH conditions. At pH=2.5, the adsorption was performed through cation exchange and the three PADs were intercalated within the Na-Mt layers. However, the adsorption capacity was lower than the theoretical cation exchange capacity of Na-Mt due to the impact of the acidic conditions on the adsorbent. At pH=7.5, only Codeine was protonated and its adsorption through cation exchange

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... esulted in the highest amount adsorbed among the tested PADs. Diazepam was adsorbed through weak electrostatic interactions, whereas Oxazepam appeared to be intercalated within Na-Mt layers despite its neutral charge. Consequently, the variation in pH strongly impacts the affinity of PADs for Na-Mt. These initial results highlight the impact of raw clay on the fate of these contaminants within environmental compartments and could pave the way for a green solution to the removal of PADs from wastewater effluents.