Enhanced Adsorption Performance of Modified Hydrotalcite with CuO for Nitrate in Wastewater

Nitrate is a type of pollutant that is increasingly prevalent in our daily lives, as well as in industrial and agricultural production. In this paper, the modified adsorbent hydrotalcite (CuO-HT) was fabricated by the impregnation method. The adsorbent was characterized by x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface analysis, and x-ray photoelectron spectroscopy (XPS). The nitrate removal performance of CuO-HT-500 was investigated using the adsorption method. The fitting analysis of the experimental results in terms of kinetics, thermodynamics, and adsorption isotherm demonstrated that the adsorption of nitrate by CuO-HT-500 conformed to the pseudo-second-order kinetic model, suggesting that chemisorption played a dominant role. The adsorption process was an endothermic reaction, which conformed to the Langmuir model and was of a monolayer nature. The results indicated that the nitrate adsorption capacity of CuO-HT-500 reached 102 mg g⁻¹. After four cycles of regeneration, the adsorption regeneration rate of nitrate in water still exceeded 83%. The modified hydrotalcite possessed high nitrate adsorption capacity and excellent regeneration performance.