Nano-biocomposite based on Zn-Ce-layered double hydroxide and Keliab for adsorptive removal of tetracycline from aqueous solutions

This study introduces a novel nano-biocomposite made from Zn-Ce layered double hydroxide (Zn-Ce-LDH) and Seidlitzia rosmarinus ashes (Keliab). The synthesized nano-biocomposite was characterized by Fourier transform infrared spectra (FTIR), X-ray diffraction patterns (XRD), field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET), and the pH drift methodology. The results demonstrated that the synthesized particles had a mean pore diameter of 27.52 nm, a total pore volume of 0.72 cm3 g−1, and a surface area of 103.69 m2 g−1. The synthesized nano-biocomposite was shown to have a much higher porosity than the Zn-Ce-LDH. Its surface area was estimated to be about 2.6 times that of Zn-Ce-LDH. The introduced nano-biocomposite (Zn-Ce-LDH/Keliab) was tested as a potential adsorbent for removing tetracycline (TC) from aqueous samples. Compared to the other common models, the Freundlich isotherm was the best adsorption model for describing the experimental results, while the pseudo-second-order model describe the kinetics of adsorption. Using the Langmuir adsorption isotherm, the maximum adsorption capacity (qmax) was estimated at around 180 mg g−1. Thermodynamic analysis showed that the TC adsorption onto Zn-Ce-LDH/Keliab was endothermic and spontaneous, as evidenced by the negative Gibbs free energy (ΔG°) and positive enthalpy (ΔH°) values. The higher removal efficiency was reached under the optimal conditions (pH = 5.0, solution temperature of 25 °C, buffer concentration of 0.15 mol L−1, the contact time of 15 min, the Keliab quantity of 0.6 g (in the nano-biocomposite synthesis stage), and the adsorbent dose of 80 mg). The fast kinetics of the developed adsorbent toward TC elimination is the best benefit of the current research. The developed adsorbent preserved approximately 65 % of its efficiency after six successive adsorption-desorption cycles. In brief, ease of manufacturing and good adsorption capacity reveal that the Zn-Ce-LDH/Keliab is a suitable adsorbent for removing TC.