3D-printing bauxite residue/fly ash-containing geopolymers as promising metal sorbents for water treatment

• Published in: Waste management (Elmsford) 2024-12, Vol.190, p.35-44
• Main Authors: Almeida, Mariana M., Gonçalves, Nuno P.F., Gameiro, Tânia, Alves, Zélia, Labrincha, João A., Novais, Rui M.
• Format: Article
• Language: English
• Subjects: Additive manufacturing; Adsorption; Aluminum Oxide - chemistry; Circular economy; Coal Ash - chemistry; Industrial waste; Industrial Waste - analysis; Polymers - chemistry; Porosity; Printing, Three-Dimensional; Red mud; Waste Disposal, Fluid - methods; Wastewater - chemistry; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - chemistry; Water Purification - methods
• ISSN: 0956-053X; 1879-2456; 1879-2456
• DOI: 10.1016/j.wasman.2024.09.007

[Display omitted] •Geopolymers were 3D-printed incorporating up to 80 wt% of industrial residues.•Metakaolin substitution with fly ash (30 wt%) improved the mechanical properties.•3D-printed porous geopolymer with highest reported compressive strength (26.9 MPa).•Printing parameters impact the final properties of porous geopolymer.•The bulk-type sorbents showed a very high affinity for lead under continuous flow. Herein, we demonstrate for the first time the feasibility of employing significant amounts (up to 80 wt%) of unexplored industrial wastes (red mud and biomass fly ash) in the production of highly porous 3D-printed geopolymer lattices envisioned for wastewater treatment applications. This without compromising the mechanical performance of the geopolymers relative to those obtained using commercial precursors. The impact of the fly ash incorporation content in the fresh-state (calorimetric and reological characterization) and hardened-state (porosity and mechanical strength) properties of the produced structures was evaluated. Moreover, the influence of key printing parameters, including nozzle diameter and geometry alignment, on the resulting properties of the lattices was also evaluated. The most promising compositions were then evaluated as lead sorbents under continuous flow. The waste-based 3D-printed lattices showed remarkable adsorption ability reaching >95 % removal efficiency after 2 h. This sustainable strategy is in line with the United Nations sustainable development goals and the transition to a circular economy, reducing the consumption of natural resources and simultaneously contributing to reducing water pollution.