3D-printed red mud/metakaolin-based geopolymers as water pollutant sorbents of methylene blue

• DOI: 10.1016/j.jclepro.2022.135315
• Publication Date: 2022-11-30T18:20:01Z
• Authors: Nuno P.F. Gonçalves; Susana M. Olhero; João A. Labrincha; Rui M. Novais
• Keywords: Metakaolin; Red Mud; Methylene blue; Black liquor; Valorisation

This work reports a novel management strategy for hazardous waste derived from the alumina industry, known as bauxite residue or red mud (RM). Herein, and first time, RM-containing porous structures were prepared by direct ink writing (DIW) then used directly to extract methylene blue (MB) synthetic wastewater. The lattices using 50:50 wt% blend between RM metakaolin (MK). incorporation of was evaluated comparing with MK-based printed structure. Despite high amount, showed compressive strength (10.7 MPa), open porosity (62.40%), very specific surface area (55 m2/g), excellent stability throughout tests (leaching, sorption, thermal regeneration). In batch adsorption tests, impact contact dye concentration evaluated. At optimized conditions ([MB]0 = 50 mg/g; time: 48 h) RM/MK-based MB uptake 19.96 mg/g, ranking them amongst best performing bulk-type (not powders) geopolymer adsorbents. Furthermore, successfully regenerated reused (up ten cycles) without compromising their performance. Their performance also corroborated under continuous-flow column experiments. These promising results demonstrate potential valorisation in wastewater treatment.