Dealumination of 3D-printed geopolymers for enhanced methylene blue removal from wastewater

Additive manufacturing allows the fabrication of complex geopolymer geometries for water and environmental applications, but 3D-printed bulk structures often have lower specific surface area (SSA) than powders, limiting their adsorption performance in advanced water treatment technologies processes. Herein, we report a post-processing strategy to overcome this limitation by using ethylenediaminetetraacetic acid (EDTA) dealumination on metakaolin-based 3D-printed geopolymers. This approach supports pollution mitigation by enhancing the adsorption performance of 3D-printed geopolymer structures. The effects of EDTA concentration and contact time on lattice physicochemical properties were systematically studied. Successful dealumination was confirmed by aluminum leaching and increased Si/Al ratios. The optimized lattice, treated with 0.1 M EDTA for 8 h, achieved a SSA of 137 m²/g - a 41% increase over the pristine structure - among the highest for 3D-printed geopolymers. Although mechanical strength decreased, the lattice retained sufficient structural integrity (2.4 MPa) for practical operation in water treatment systems. In methylene blue adsorption tests, the modified material reached a maximum uptake of 30.86 mg/g and removal efficiencies above 98% at pH 10.5 (C₀ = 165 ppm). The lattices were successfully regenerated, maintaining >93% removal after 10 adsorption-desorption cycles. These results demonstrate that EDTA dealumination is an effective surface-engineering approach to enhance SSA and adsorption in 3D-printed geopolymer structures, supporting improved mitigation of water pollution and sustainable use of environmental resources.