Efficient Nitrate Removal from Water Using Zinc-Aluminium Layered Double Hydroxide Nanostructures: Synthesis and Adsorption Optimization

Layered double hydroxides (LDHs), distinguished by their lamellar nanosheet structures, are highly effective materials for hosting and intercalating functional chemicals, making them suitable for water contaminant remediation. Elevated nitrate (NO3−) levels in water and wastewater, attributed to the high solubility of nitrates, pose significant risks to aquatic ecosystems and human health. This study outlined a simple co-precipitation method for synthesizing zinc-aluminum Zn-Al-LDHs and evaluated their performance in efficiently removing nitrate ions under optimal conditions. The characterization of the Zn-Al-LDH nanostructures was conducted through various techniques, including X-ray diffraction (XRD), thermogravimetric and differential thermal analyses (TGA/DTA), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). Key parameters influencing nitrate adsorption, such as NO3− concentration, pH, adsorbent dosage, contact time, and temperature, were thoroughly examined in a systematic manner. Notably, the calcined form of LDH (Zn-Al-LDH-C) exhibited the highest nitrate adsorption capacity of 94%, with optimal adsorption at pH 6.9 and low temperature. Equilibrium was reached in 80 minutes, and the adsorption capacity rose to 16 mg/g. FTIR analysis confirmed the intercalation of nitrate ions into the calcined material. Adsorption isotherm studies revealed that nitrate adsorption onto Zn-Al-LDH followed the Langmuir model (R²=0.99), indicating a uniform surface and monolayer adsorption mechanism, as opposed to the Freundlich model (R²=0.90). This study demonstrates the potential of enhancing Zn-Al-LDH-C nanostructures to improve their efficiency in removing contaminants from water and wastewater, presenting a promising approach for advanced water treatment solutions.