Synthesis and aldehyde absorption properties of aspartate-octacalcium phosphate inclusion compound Original Research Article

Double salt of octacalcium phosphate (Ca8(HPO4)2(PO4)4·5H2O; OCP) and aspartate (−OOCCH2CH(NH2)COO−; Asp) was synthesized by hydrolysis of α-tricalcium phosphate (α-Ca3(PO4)2; α-TCP) in the presence of sodium aspartate. The compositional formula of the obtained inclusion compound (Asp-OCP inclusion compound) was Ca8(HPO4)1.28(C4H5NO4)0.72(PO4)4·6.3H2O, which included higher content of aspartate than that in our precedent paper. Asp-OCP inclusion compound reacted with aldehdyes in the interlayer. In the absorption experiments using formaldehyde gas, the amounts of absorption for Asp-OCP inclusion compound was approximately twice as that for activated charcoal (for Asp-OCP inclusion compound: 3.1×10−3 mol/g, activated charcoal: 1.6×10−3 mol/g), in spite that the BET specific surface area of Asp-OCP inclusion compound was approximately one-thirtieth part of that of activated charcoal (Asp-OCP inclusion compound: 43 m2/g, activated charcoal: 1225 m2/g). When the gas absorption experiments using acetaldehyde and leaf aldehyde under higher concentrations were carried out, the imine formation in the interlayer were observed in FT-IR and solid state 13C-NMR spectra.