3D printing of a photo-curable hydrogel to engineer hierarchical porous mechanically robust 3D structure for ion capture or sustained potassium ferrate(VI) release

Contaminated water and scarcity of clean water are becoming progressively serious environmental concerns. Removal of hazardous pollutants from wastewater is vital and urgently needed attention for the protection of pure water resources. To tackle the aforementioned challenges, macroporous structures have great potential to be used in the treatment of heavy metal ions to improve the adsorption efficiency and sustainability of wastewater treatment methodologies. In this context, additive manufacturing technologies have gained considerable attention because of their ability to construct intricate macro-porous shapes with multifunctionalities via diverse materials. Here, we used a photocrosslinking graft copolymerization of polyvinyl alcohol (PVA) and acrylic acid ink in the presence of Norrish type II photosensitizer through the hot-melt extrusion-type 3D printer coupled with an in-place UV irradiation to improve the printing quality of crosslinked ink with regards to producing a 3D hierarchically porous structure. The photocured inks offered strong shear-thinning behavior that allowed layer-by-layer deposition to generate well-defined 3D structures while having sufficiently high viscoelasticity to retain the shape after the printing process. With an adequate viscosity at higher extrusion shearing forces, the 3D printed structure could create tall, multifaceted scaffolds with an internal lattice structure that possesses microscale porosity. The 3D hierarchically porous structure shows a recoverable yet robust matrix, capable of effectively removing heavy metal ions from water with fast-responsiveness and a high capacity. The ferrate(VI)-contained capsule-like was detected to be efficient regarding COD reduction and decolorization of real wastewater from decolorization. Such 3D-printed hierarchical macroporous objects can offer great prospects in the treatment of water and wastewater purification applications.