Dual functional oyster shell-derived Ag/ZnO/CaCO₃ nanocomposites with enhanced catalytic and antibacterial activities for water purification

Transforming biological waste into high value-added materials has attracted extensive current research interest in the wastewater treatment field. In this study, oyster shell-derived CaCO₃ was used as a solid support to construct efficient Ag/ZnO/CaCO₃via Cacumen platycladi extract. As compared to binary Ag/CaCO₃ and ZnO/CaCO₃, the as-obtained Ag/ZnO/CaCO₃ exhibits excellent performance for the reduction of 4-nitrophenol (4-NP) with a reduction rate of 97.6% within 8 minutes. Furthermore, Ag/ZnO/CaCO₃ exhibited superior antibacterial activity in inhibiting the growth of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) with minimum inhibition concentrations (MICs) of 60 μg mL^-1 and 30 μg mL^-1, respectively. The observation of the superior activity for the reduction of 4-NP and antibacterial test of Ag/ZnO/CaCO₃ can be attributed to the synergistic effect of Ag, ZnO and the oyster shell-derived CaCO₃. This study provides a strategy in developing highly efficient catalysts for the reduction of 4-NP and antibacterial agents based on the oyster shell-derived CaCO₃.