Development of colored geopolymers using Maya blue-based pigments

Poster presented at the 8th Mid-European Clay Conference, held in Kosice (Slovakia) on July 4-8th, 2016. S6: application and treatment of clays and other industrial minerals.Geopolymers are inorganic amorphous silicon-based polymers materials of increasing scientific and industrial interest especially for engineering applications. Diverse types of clay minerals are currently explored as source in the production of such materials which are prepared at very high pH media. For certain applications it would be interesting to produce colored geopolymers, however the direct incorporation of organic dyes was not easy as they may become degraded under the extreme basic conditions used during the synthesis. In this communication, we will report a new approach that uses the concept of ancient Maya Blue pigment to encapsulate diverse organic dyes in the structural tunnels of the fibrous clay to be protected once incorporate as a pigment during the geopolymer formation. Sepiolite is relatively stable in basic media and dyes such as methylene blue (MB) and methyl red (MR) present a convenient size to be adsorbed in the clay inside its structural nanopores. In this way, when the geopolymer is formed the encapsulated organic dye is preserved and the final products show colors that made fade a little with the evolution of the polymerization reaction but remain still persistent with time once the reaction ends. The resulting colored geopolymers are highly stable to treatments with hydrogen peroxide, UV irradiation or in acid conditions. This preliminary study [1] is a first example that may open way to other approaches for functionalizing inorganic binder materials with organic elements sensitive to thermal treatments used in conventional ceramic processing.CICYT (Spain, project MAT2012-31759 & MAT2015-71117-R) and the EU COST Action MP1202