High adsorption selectivity of ZnAl layered double hydroxides and the calcined materials toward phosphate

The selective adsorption of phosphate ions was investigated on CO32-, Cl−, and NO3--type ZnAl layered double hydroxides (LDHs) and the calcined CO32--type LDH at 200, 400, 600 and 800 °C, respectively. The calcined LDHs and NO3--type LDH showed high selectivity toward phosphate ions, while the Cl−-type LDH shows selectivity toward both SO42- and phosphate ions. The NO3--type LDH selectively adsorbed phosphate ions mainly through ion exchange. The calcined samples possibly proceed through ligand complexation or electrostatic attraction between phosphate ions and hydrated ZnO formed after calcination, although the structural memory effect was observed for the samples calcined below 600 °C with the formation of CO32--type LDH. Adsorption/desorption behaviors indicated that the calcined samples had good stability and reusability.

A high selectivity toward phosphate and reusability were exhibited by the calcined ZnAl–CO3 LDHs at different temperatures.Figure optionsDownload high-quality image (75 K)Download as PowerPoint slide