Synthesis of calcined LDHs materials decorated on ZnO nanorods: enhancing adsorption capacity and antibacterial activity

Abstract

In this study, ZnCo-layered double hydroxides (ZnCo-LDHs) were successfully synthesized via a co-precipitation method using zinc nitrate and cobalt nitrate in a 3 : 1 molar ratio on ZnO rods (ZnO/ZnCo-LDHs). Subsequent heat treatment of the ZnO/ZnCo-LDHs at 600 °C transformed them into ZnCo₂O₄ and ZnO, which were evenly distributed within the ZnO rods. The adsorption capacity of Reactive Blue 221 (RB221) using the ZnO/ZnCo-cLDHs composites reached 75.74 (mg g⁻¹) in 100 min under the following conditions: initial RB221 concentration of 80 ppm, pH 7, and a dose of 1.0 g L⁻¹. The mechanism of dye adsorption on the ZnO/ZnCo-cLDHs was determined by the “memory effect” of oxide and available vacant sites between interlayers of adsorption mixtures. The Langmuir adsorption isotherm was more efficient in explaining the adsorption of RB221 dye on ZnO/ZnCo-cLDHs than the Freundlich isotherm. Experimental data indicated that the second-order kinetic equation is a more suitable model for describing the adsorption process than the first-order kinetic equation. Furthermore, the ZnO/ZnCo-cLDHs composites demonstrated antibacterial properties, inhibiting the growth of Escherichia coli, Staphylococcus aureus, and Salmonella typhimurium.