Capacity, selectivity, and reversibility for nitrate exchange of a layered double-hydroxide (LDH) mineral in simulated soil solutions and in soil

The leaching of nitrate is an important way of N losses from agricultural soils in humid regions. Nitrate leaching is difficult to control as most soils under crop production do not have anion-exchange properties, and nitrate remains mobile in the solution. The present work evaluated the potential use of a synthetic layered double-hydroxide (LDH) mineral as a nitrate exchanger in soil. The LDH used was a chloride form of a magnesium-aluminum layered double hydroxide with the formula: [Mg²⁺ ₀.₈₂Al³⁺ ₀.₁₈(OH)₂]⁰.¹⁸⁺[(Cl⁻)₀.₁₈ 0.5(H₂O)]⁰.¹⁸⁻. Experiments were carried out in aqueous solutions as well as in soil with the following objectives: (1) to characterize the nitrate adsorption capacity on the LDH, (2) to study its selectivity for nitrate adsorption in solution, (3) to evaluate the reversibility for nitrate exchange, and (4) to study the nitrate adsorption capacity and nitrate diffusion towards the LDH in soil.