Use of a clay mineral and its nonionic and cationic organoclay derivatives for the removal of pharmaceuticals from rural wastewater effluents

Abstract : A Na+ exchanged montmorillonite clay (Na-Mt) and its organoclay derivatives prepared with benzyldimethyltetradecylammonium (BDTA) cationic and polyoxyethylene(20)oleyl-ether (Brij-O20) non-ionic surfactants were used for first time at our knowledge as adsorbents the removal diverse pharmaceuticals (PPs) from samples collected in a rural wastewater facility (town of Josnes in France). The selected facility showed a poor efficiency for the elimination of PPs that were permanently release to the environment. Although involving different interactional mechanisms, the whole adsorbents Na-Mt, nonionic Brij-Mt and cationic BDTA-Mt organoclays, could remove the entire PPs of various chemical nature in a low concentration regime (ng L-1), where electrostatic interactions mainly controlled the adsorption. Thus, the organic PPs cations were preferentially adsorbed onto Na-Mt and Brij0.4-Mt (with its dual hydrophilic-hydrophobic nature) while anionic PPs showed a bold affinity to BDTA-Mt. The hydrophobic environment generated by the intercalation of surfactants within the interlayer space of organoclays conferred a versatility for the adsorption of numerous PPs through weak molecular forces (Van der Waals and/or pi-pi interactions). The study confirmed the proper efficiency of the studied layered materials including organoclays and emphasized about their promising interests in water remediation strategy.