Influence of the synthesis method of layered double hydroxides on the textural properties and nitrate removal

Layered double hydroxides were prepared by co-precipitating Mg2+ and Al3+ ions at constant pH. Three different methods of solution additions and two temperatures for synthesis and aging were tested in each method. Through X-ray diffraction, it was confirmed that all the synthesized solids have a hydrotalcite-type structure, obtaining more crystalline compounds when one solution of Mg/Al is added to another whit CO3-/OH- and compounds with greater interlaminar spacing when three different solutions are added (Mg/Al, CO3- and OH-). In addition, the solids obtained by this last method have a higher specific surface area and total pore volume, as confirmed by the N2 adsorption-desorption. A similar trend occurs with synthesis and aging temperatures where better textural properties are obtained at a higher temperature, reaching surface area values of 242 m2/g and pore volume of 0,93 cm3/g. All the synthesized solids were active for removing nitrates in water, obtaining the best results with the samples prepared by dripping three different solutions at 60 °C (26 mgNO3-/g.) This fact demonstrates the correlation between the synthesis method and the textural properties of the material with its potential application in removing contaminants.