Anion substitution of nitrate-saturated layered double hydroxide of Mg and Al

In the context of producing industrial-grade hydrotalcite-like (HT) materials containing phosphate and sulfate for use as slow-release fertilizers, the ease with which nitrate-HT can be converted to phosphate-HT and sulfate-HT has been examined. Graded amounts of di-ammonium hydrogen phosphate and ammonium sulfate were added to nitrate-HT, while maintaining pH at 9.5, to produce substitutions ranging from approximately 50% to 100%. Chemical and X-ray diffraction analysis of the products confirmed that the substitution could be easily effected by simple topotactic exchange.