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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. [Display omitted] • A novel strategy for geopolymer adsorption sieve based on direct ink writing was proposed. • The geopolymer adsorption sieves with high molding accuracy and good pore distribution were successfully prepared. • The geopolymer adsorption sieves exhibit considerable dynamic and static adsorption properties. • The adsorption mechanism was proposed based on experiments and DFT calculation. [ABSTRACT FROM AUTHOR]

Designing efficient visible light photocatalysts is targeted to improve the solar utilization to ameliorate environmental problems. Ag 10 Si 4 O 13 has great application potential due to a narrow band gap and the existence of internal electric field（spontaneous polarization electric field inside the crystal）. Here, a novel and convenient synthetic strategy based on sol-gel method and template method was proposed to fabricate 3D sponge-like hierarchical pore Ag 10 Si 4 O 13 (HPA) microblock with enhanced photocatalytic activities. The group multiple coordination is conducive to further improve the dispersion of Ag 10 Si 4 O 13 precursor around polystyrene (PS) microsphere. Weak sintering between nano-Ag 10 Si 4 O 13 particles ensured the formation of sponge skeleton structure. Compared with Ag 10 Si 4 O 13 , HPA showed enhanced separation efficiency of electron hole pairs due to the carbon doping. And the uniform and well-developed pore structures further improved the photocatalytic performance. As a result, HPA (P-5) exhibited a degradation efficiency of 98.98% at 30 min under visible light, and an excellent cycle performance were obtained. The proposed strategy provides an important reference for the preparation of easily recoverable microblock photocatalyst. [Display omitted] • Green synthesis methods, keeping synthesis and environmental impact to a low threshold. • Multi-coordination between Ag 10 Si 4 O 13 precursor and PS resulting in a 3D sponge-like hierarchical pore. • Dual function of internal electric field and C doping enhanced photogenerated carrier separation efficiency of Ag 10 Si 4 O 13. [ABSTRACT FROM AUTHOR]

The practicability of nano-powder photocatalyst is limited by the difficulty of its recovery. 3D monolithic TiO 2 photocatalyst (MTP) was printed by direct ink writing (DIW) using TiO 2 nanoparticles as solutes of tetrabutyl titanate precursor to configure printing slurry to achieve integrated regulation of microscopic and macroscopic pore structure. The SEM verified that the surfaces of skeleton-TiO 2 particles were uniformly covered by the TiO 2 nanoparticles derived from calcining gel. And a highly connected hierarchical pore structure was formed by the skeleton-TiO 2 particles and the designed 3D printing macroscopic pores, which laid the foundation for rapid capture and efficient in situ degradation of antibiotics. The nano TiO 2 powders prepared by calcined gel have narrow band gap width, which is easier to generate electrons and holes and have low recombination rate. Therefore, the core-shell structure constructed by nanoparticles derived from gel and commercial TiO 2 can effectively optimize the photocatalytic performance of MTP. The removal of tetracycline hydrochloride (TCCH) in water by MTP was used to verify the application effect of macro structure in practice, and the synergistic effect of adsorption and degradation kinetics was summarized. The dynamic adsorption effect of MTP reached 97.44 % at pH 7 for 5 h. Under simulated sunlight, MTP exhibited a synergistic adsorption-degradation effect, reaching equilibrium at 210 min. The cycle test shows that the removal rate of TCCH by MTP remains 91 % after 4 cycles. This strategy provides a good reference for the assembly of nanosemiconductor materials into environmentally friendly 3D structured systems. [Display omitted] • A novel strategy for 3D TiO 2 photocatalyst based on direct ink writing was proposed. • The 3D TiO 2 photocatalyst with high molding accuracy and good pore distribution were successfully prepared. • The microstructure of 3D TiO 2 photocatalyst is a core-shell structure in which small particles wrap large particles. • The 3D TiO 2 photocatalyst exhibit considerable dynamic adsorption and degradation properties. [ABSTRACT FROM AUTHOR]