Fbrication And Wettabilitycharacteristics Of Hollow Ca-Alginatehydrogel Fibers

Hollow hydrogel fiber is a kind of water containing fiber with a cross-section cavity along the fiber axis characteristized with high specific surface area, porosity, hypotoxicity. Ca-alginate Hollow hydrogel fiber combines the structure advantages of hollow fibers and the hydrophilicity of Ca-alginate hydrogel. Hence, it can be widely applied in the fields like ion adsorption, water treatment, drug release, and tissue engineering. Commonly methods for hollow hydrogel fiber preparation are physical template methods based on structure control, such as hollow tube spinning method, the centrifugal casting method. However, relatively few studies focued on utilizing the speed difference of bidirectional diffusion between polymer molecules and external cross-linking ions during the gelation process. This research utilized the Hydrodynamic spinning methods, with alginate as spinning solution, divalent calcium ions as cross-linking agent to fabricate hollow calcium alginate hydrogel fibers with underwater super-oleophobic property.This paper fabricated uneven Ca-alginate hydrogel structures from solid to hollow induced by ion diffusion speed differences. We analyzed the influences of parameters like tip diameter, concentration of spinning solution and cross-linking ion on hydrogel structures. Verified the hollow structures with scanning electron microscopy (SEM), fluorescence micro-scope. Characterized the surface wettability use the contact angles, which is a parameter describing fiber wetting ability or wetting degree. Prepared hydrogel fibers are taking Oil/Water separation efficiency test after freeze drying.The experimental results show that hollow Ca-alginate hydrogel fibers are slender uniform filaments with underwater oleophobic property. After treating by freeze drying methods, dried Ca-alginate hydrogel fibers can selectively absorb the water component out of the water/oil mixture with a relatively high separation efficiency. We designed the forming process of the hollow Ca-alginate hydrogel fiber and researched the relations between the parameters and hollow structures. Finally, we determined the fiber diameters depend on the needle diameters and the hollow structures affected by ion concentration. Because the calcium ion and sodium alginate molecular diffusion at different speed, the speed difference induced the structures from solid to solid-hollow and hollow structure. Underwater oil contact Angle data revealed that Ca-alginate fibers have oil water contact angles around150°for five kinds of test oils, showing the underwater super-oleophobic property. Dried Ca-alginate hydrogel fibers absorbing water selectively, possess excellent water oil separation ability. Solid-hollow and hollow hydrogel fiber still have Oil-water separation efficiency higher than80%at20%oil-water mixture ratio, much better than that of solid hydrogel fibers.