Adsorption of Ciprofloxacin and Lidocaine by Non-Fibrous Raw Mg-Clays: The Role of Composition and Texture

Abstract

This study evaluated non-fbrous Mg-clays as potential adsorbents of emerging contaminants (ECs) from water. The materials were characterized, and their textural and structural propertieswere related to their ability to remove two model EC molecules: ciprofloxacin (CPX) and lidocaine(LID). The results showed that Ad-6 and Ad-7 are mixed-layer kerolite/stevensite, while Ad-5 andAd-8 are mainly composed of smectite minerals like stevensite and saponite, respectively. Ad-8exhibited the highest CPX-adsorption capacity (0.91 mmol·g−1 clay), likely due to its saponite content. Mixed-layer materials also performed well, with Ad-6 and Ad-7 achieving an adsorption capacity of 0.8 and 0.55 mmol·g−1 clay, respectively. Adsorption studies suggested that CPX is adsorbed through ion exchange in materials with high smectite content (Ad-8 and Ad-5), while interstratifed materials showed enhanced retention due to kerolite presence, which improves their porous structures. Similar fndings were observed for LID, indicating a cationic-exchange mechanism for LID adsorption in all the materials and suggesting that the molecular size of the EC could regulate the removal capacity of these materials. This work showed that the studied Mg-clays could be effectively used for the removal of pharmaceutical pollutants, expanding their commercial possibilities.