Optimum conditions for intercalation of lacunary tungstophosphate(V) anions into layered Ni(II)–Zn(II) hydroxyacetate

Abstract

Acetate containing nickel–zinc hydroxysalts (LHS-Ni–Zn) have been synthesized by coprecipitation and hydrothermal treatment. The acetate anions were exchanged with PW 12O 40 3− anions, and optimum conditions to attain the maximum level of W in the compound have been identified. The W intercalated compound was characterized by powder X-ray diffraction, FT-IR spectroscopy, thermogravimetric and differential thermal analyses, scanning electron microscopy and transmission electron microscopy. The exchange of LHS-Ni–Zn with PW 12O 40 3− at pH=3 for 72 h leads to a solid with a basal spacing of 9.62 Å and a W content (weight) of 37%. The hydrothermal treatment at 90 °C for 24 h increases this value to 48% with a W/Zn molar ratio of 1.38, which corresponds to a layered compound with lacunary tungstophosphate anions in the interlayer space. The intercalated solid is stable up to 250 °C, the layer structure collapses on dehydroxylation and amorphous compounds were identified at 500 °C. Two crystalline phases, NiO (rock salt) and a solid solution (Zn 1− x Ni x )WO 4, were identified by powder X-ray diffraction at high temperature (ca. 1000 °C).