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

Double salt of octacalcium phosphate (Ca-8(HPO4)(2)(PO4)(4).5H(2)O; OCP) and aspartate (-OOCCH2CH(NH2)COO-; Asp) was synthesized by hydrolysis of alpha-tricalcium phosphate (alpha-Ca-3(PO4)(2); alpha-TCP) in the presence of sodium aspartate. The compositional formula of the obtained inclusion compound (Asp-OCP inclusion compound) was Ca-8(HPO4)(1.28)(C4H5NO4)(0.72)(PO4)(4).6.3H(2)O, 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 x 10(-3) mol/g, activated charcoal: 1.6 x 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 m(2)/g, activated charcoal: 1225 m(2)/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 C-13-NMR spectra. (C) 2003 Elsevier Ltd. All rights reserved.