Sviluppo di membrane geopolimeriche tramite Cold Sintering Process

The aim of this thesis was the recycling of waste geopolymer to produce geopolymeric membranes in view of their possible use in the removal of environmental pollutants through ultrafiltration. The samples were prepared in collaboration with the "Geopolymers" group of the Institute of Science, Technology and Sustainability for the development of Ceramic Materials (CNR-ISSMC) of Faenza, where the characterizations were also carried out. The first prototypes of filter membranes will be tested in the Department of Environmental and Prevention Sciences of the University of Ferrara, as part of the PNRR ECOSISTER project. The preparation of the materials took place in two phases: in the first one, a fraction of geopolimeric waste was replicated. Then the geopolymer mixture sodium or potassium-based was prepared. The latter, having a Si/Al=2.0 ratio, was obtained from metakaolin and potassium disilicate solution; the sodium-based one was synthesized by adding a 12 M NaOH solution to the metakaolin. In the latter case, the presence of the Na+ cation and a Si/Al ratio=1.2 allowed the in situ nucleation of the NaA zeolite, obtaining composite material. The slurries were poured into a mold and consolidated in a heater, producing samples which were subsequently ground and sieved, obtaining powders with a size of less than 200 μm. In the second phase, a reactive solution was added to the powders, that were then consolidated using the "Cold Sintering Process". With the aim of obtaining materials with different degrees of densification, the second phase of the synthesis was carried out by varying: mold temperature, applied pressure and reactive solution. The evaluation of the different process parameters allowed the selection of some samples. These, considered the right compromise between densification, synthesis conditions and reproducibility, were then reproduced and subjected to mechanical compression tests, porosimetry and electron microscopy test.