Facile synthesis of porous geopolymers via the addition of a water-soluble pore forming agent

A facile and effective route for the fabrication of porous geopolymers through the addition of a water-soluble pore forming agent (NaCl) is proposed in this study. NaCl/geopolymer samples were firstly obtained using metakaolin and slag as raw mineral materials combined with sodium-based alkali activator and NaCl as a sacrificial (soluble) template. After a simple extraction step by water, porous geopolymer were obtained. The effect of NaCl content on the pore morphology, porosity, density, boiling water absorption, and mechanical and structural characteristics of the synthesized porous geopolymers was investigated. High porosity (67.4–80.4 vol%) metakaolin/slag-based geopolymers, possessing also a high ratio of open porosity to total porosity (77.4–84.0%) and a good compression strength (2.4–7.0 MPa), were produced. The adsorption properties for methylene blue removal were investigated as well. The high strength bulk-type waste-based geopolymer adsorbents by this water-soluble templating method is suitable for applications in wastewater treatment systems.