Sustainable Fabrication of Ca/Al-Layered Double Hydroxide (LDH)-Coated Sand from Marine Waste for Efficient Removal of Tetracycline Contamination in Water

The aim of this study was to formulate a reactive composite for treating the antibiotic contaminated water. Calcium-Aluminum (Ca/Al) bilayer hydroxide (LDH) nanoparticles were immobilized on the surface of inert sand to obtain an effective adsorbent for the removal of tetracycline (TC) from water. A sustainable approach was used to prepare these particles. From low cost alum, Al³⁺ ions were extracted and from shellfish waste, marine waste was used to extract calcium ions (Ca²⁺) at an optimum concentration of 9000 mg/L of acetic acid. A surfactant SDS was used to improve the dispersion and uniformity of the coating of the nanoparticles on the sand surface. The synthesis conditions were systematically optimized by the study of the effects of the pH, the surfactant dosage, the calcium to aluminum (Ca/Al) molar ratio, and the quantity of sand added. It was found that the best parameter for the preparation of the adsorbent was pH 8, 0.1 g of SDS, 1:1 Ca/Al molar ratio and the ratio of sand to 50 mL solution, which is 1 g per 50 mL. In this scenario, the coated sand removed 54.1% of tetracycline after 3 h of contact in the presence of an initial concentration of 40 mg/L. The results showed that the surfactant SDS was much more effective than the surfactant CTAB for all the experiments. The successful deposition of Ca/Al-LDH nanoparticles onto the sand surface was confirmed through material characterization assays (XRD, FTIR and SEM) that revealed a lamellar structure, which greatly increased the surface reactivity of the inert substrate. The study introduces a sustainable marine biological waste-to-nanomaterials conversion process that offers a cost-effective, eco-friendly solution to address antibiotic pollution in wastewater.