Highly effective and reusable nanometal/carbon-coated snail shell for the sequestration of metronidazole: decontamination and disinfection

This study investigates the adsorption efficiency of metronidazole (MTZ) from aqueous solutions using snail shell (SSB) and carbon-coated zinc oxide-modified snail shell (SCZ) nanocomposites. Key factors influencing adsorption capacity, including pH, contact time, adsorbent dose, MTZ concentration, and temperature, were systematically evaluated. The maximum adsorption capacities were 25.96 mg g^-1 for SSB and 35.13 mg g^-1 for SCZ, with optimal adsorption occurring at pH 3 after 180 min of contact. Kinetic analysis revealed that the pseudo-second-order model best fit the experimental data, while adsorption isotherms followed the Langmuir model for SSB and the Freundlich model for SCZ, indicating different adsorption behaviors. Thermodynamic analysis showed that adsorption was spontaneous, endothermic, and entropy-driven. MTZ desorption was effectively achieved using ethanol, demonstrating good reusability of the adsorbents. This study highlights the potential of SCZ nanocomposites as an effective, sustainable solution for removing MTZ from aqueous systems.