Uptake and Release of Sodium Diphosphate by a Chloride-Type Layered Double Hydroxide

Abstract

In this study, we investigated the uptake and release of sodium diphosphate (Na4P2O7, P2) by a chloride-type layered double hydroxide (LDH-Cl) with good anion exchange properties. The pH of the P2 aqueous solution produced the strongest effect on the P2 uptake. At pH 5, the maximum uptake was 1.9 mmol/g (LDH-P2(1.9)), and the minimum uptake amount obtained at pH 11 was 0.8 mmol/g (LDH-P2(0.8)). The maximum release rate of P2 determined for LDH-P2(0.8) in a NaCl aqueous solution at a NaCl(aq) concentration of 4 M, temperature of 24 °C, and reaction time of 1 h was 12%. After repeating the release process four times under these conditions, the cumulative P2 release rate increased to 22%. Meanwhile, the cumulative release rate of P2 in a Na2CO3 aqueous solution determined for LDH-P2(0.8) was 90%, which exceeded the value obtained for the NaCl aqueous solution.