Regeneration and Reuse of Hydrotalcite-Like Anion Exchanger with High Selectivity to Phosphate Anion

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Regeneration methods of Mg-Al-Cl form hydrotalcite-like ion exchanger for selective adsorption of phosphate anion were investigated. It was possible to regenerate the reusable exchanger with high efficiency by the two-step regeneration method consisting of the treatment with a mixture of 0.25 mol ·kg-1-NaOH and 6.00 mol·kg-1 NaCl solution at the first step, followed by that with 3.68 mol·kg-1 MgCl2 solution. The exchanger could be used for removal of phosphate ion with regeneration ratio of 50% even after nine times reuse. The regeneration ratio of the exchanger with granular form was examined in a flow system and found to be almost equal to 100% using the two-step regeneration method. The break-through capacity of the flow system was more than those of well-known zirconium ferrite type adsorbents even after six times runs.