Easy route to activate clay honeycomb monoliths for environmental applications

In this study a simple method to activate clay honeycomb monoliths is proposed. It consists of mixing the clay with coal before the extrusion, and further removing the coal from the monolith by heating under air at the lowest possible temperature. This procedure is an easy, non-destructive and economical way of activating clay monoliths by an enhancement of their porosity. Characterization techniques such as N2 physisorption, mercury porosimetry and scanning electron microscopy (SEM) showed an improvement of the clay textural properties as a consequence of carbon burning. X-ray diffraction with Rietveld analysis indicated that no significant structural modification of the clay took place. Axial crushing tests demonstrated that there was no worsening of the mechanical strength in the resulting activated monoliths. Finally, investigation of their performance in methylene blue adsorption experiments suggested that the route here proposed could be an alternative to acid activation methodologies. In particular, the results are interesting for those applications in which combination of the honeycomb monolithic design and the improvement of macroporosity may represent an advantage.