Intercalation of melamine into layered zirconium phosphates and their adsorption properties of formaldehyde in gas and solution phase

The intercalations of melamine into α- and γ-zirconium phosphates (α- and γ-ZrP) were investigated. Melamine-intercalated α-ZrP afforded two phases with different interlayer distances (d = 1.30 and 1.55 nm). The phase with d = 1.30 nm was obtained as the mixture with original α-ZrP at 30 min reaction by batch method, whereas the single phase with d = 1.55 nm was obtained by decantation method in saturated melamine aqueous solution. Contrary to this, for γ-ZrP a phase with d = 1.78 nm was obtained by both batch and decantation methods in saturated melamine aqueous solution. And new phase with d = 1.48 nm was formed in batch method at low pH or lower concentration of melamine aqueous solution. In these phases the arrangement of melamine changed from a monolayer structure to a bilayer structure with the increase of interlayer distance. Furthermore, melamine-intercalated α- and γ-ZrP adsorbed formaldehyde gas and formaldehyde in formalin solution by interacting with melamine molecule in the interlayer region. In melamine-intercalated γ-ZrP with d = 1.48 nm, the expansion of interlayer distance to around 1.6 nm was observed after the adsorption of formaldehyde gas and formaldehyde in formalin solution. The adsorption of formaldehyde in formalin solution was accompanied with the release of melamine in the interlayer region with increasing the concentration of formaldehyde at 65 °C.

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