Nickel-iron layered double hydroxide (LDH): Textural properties upon hydrothermal treatments and application on dye sorption

NiFeCO₃ hydrotalcites with Ni/Fe molar ratio of 3 were synthesized by co-precipitation method at constant pH, followed by hydrothermal treatment at various temperatures 85-180 °C for 3-360 h. The obtained materials were characterized by XRD analysis, FT-IR spectroscopy, SEM and TEM microscopy, TGA and BET techniques. The resulting materials were found to be similar to the hydrotalcite with a well-defined hexagonal morphology of crystallites. The hydrothermal treatment and aging time increases the platelet sizes and decreases the surface area. XRD analysis showed the formation of sharper and intense peaks, which might indicate the larger crystallites size of LDH as well as higher crystallinity. Furthermore, textural studies revealed influence of aging time and temperature on the properties of the crystalline phase. The prolonged time tends to form additional products, identified as NiFe₂O₄ spinel and NiO nickel oxide. The effect of hydrothermal treatment temperature on the kinetics of dye removal has been explored. It was found that the percentage color removal increases with increasing hydrothermal treatment temperature up to 140 °C and aging time up to 4 days. Furthermore, the color removal decreases with increasing hydrothermal treatment temperature up to 140-180 °C and prolonged aging time.