3D printed geopolymer adsorption sieve for removal of methylene blue and adsorption mechanism

Geopolymers have high application potential due to their outstanding ion exchange ability. A novel direct ink writing (DIW) geopolymer adsorption sieve (GAS) preparation strategy was proposed. The preparation and optimization of DIW inks and the adsorption properties and mechanism of GAS for methylene blue (MB) were systematically investigated by characterization and density functional theory (DFT) calculation. The GASs exhibited desired adsorption rates for MB in both dynamic (83.6% at 200 min) and static (97.1% in 7 days) states. The adsorption kinetic was fitted well by the pseudo-first-order model at the early stage and eventually was transformed to fit well by the pseudo-second-order model and indicated the boundary liquid layer diffusion and intraparticle diffusion were all rate-limiting factors. The exploration of adsorption mechanism confirmed that the adsorption of GAS for MB was affected by the coordination of electrostatic action, hydrogen bonds and electrons transfer. The proposed strategy provides a promising reference for design and preparation of eco-friendly 3D printing adsorbent systems.