Synthesis of porous phosphate-based geopolymers via replica shaping for potential application in biomedicine

Phosphate-based geopolymers (PGP) are a new type of geopolymers that have recently been studied due to the unresolved formation mechanism, as-achieved (micro)structure and possible applications. Thanks to their non-alkaline environment, PGPs have many advantages over alkaline analogues such as lack of efflorescence and better thermal properties. PGPs resemble to human bones and teeth (whose main constituents are calcium phosphates) stressing out their biocompatible application. PGP are usually obtained by mixing an aluminosilicate precursor with an acidic source of phosphate. In this work, we investigated the feasibility of preparing porous PGP from metakaolin and phosphoric acid via replica shaping. Polyurethane (PU) template was infiltrated by the geopolymer paste until a homogeneous green body was achieved. Green bodies were cured in a sealed vessel at 60 ℃ for 24 h in order to solidify their shape, while thereafter porous geopolymer ceramics were obtained by heat treatment to 600 °C at a rate of 1 ℃ min-1 enabling PU burnout. Samples were characterized through their porosity and morphology (SEM and adsorption behaviour) and chemical structure (XRD and ATR-FTIR). Consequently, with all of the aforementioned advantages, PGPs porous bodies were shown worthy of further investigation for fostering biomedical application.