Porous metakaolin-based geopolymers for adsorption of Contaminants of Emerging Concern from wastewaters

This research investigates the applicability of metakaolin-based geopolymers in the removal of organic contaminants of emerging concern from polluted water by adsorption. Ofloxacin and cortisone were chosen as model molecules, because of their different chemical properties. For each contaminant, adsorption was first tested on powdered materials with different mesoporosity. The removal of the two drugs was eventually evaluated on macroporous geopolymer monoliths, obtained using commercial olive oil and H2O2 solution as pore-forming agents to enhance permeability to liquids and thus favor the absorption process. Finally, a novel ceramic composite diaphragm was prepared and tested. Adsorption experiments demonstrated the larger affinity of all substrates for ofloxacin than for cortisone. Different adsorption mechanisms were observed, monolayer for the antibiotic and cooperative for the steroid, with different adsorption capacities, 29(2) mg g−1 and 0.47(2) mg g−1, respectively. The removal efficiencies of the two drugs by the monoliths and by the ceramic composite diaphragm were evaluated and compared. Satisfactory drug recoveries (>99%) were also obtained under realistic conditions, i.e., freshwater, micrograms per liter drug concentration.