Sustainable Route to Inorganic Porous Hollow Fibers with Superior Properties

Abstract

This paper presents a method for the fabrication of inorganic porous hollow fibers, using ecologically benign feed materials instead of organic solvents and harmful additives. Our method is based on ionic cross-linking of an aqueous mixture of sodium alginate, inorganic particles, and a carbonate. The mixture is spun into an acidic coagulation bath, where the low pH triggers the dissociation of the carbonate into multivalent cations and carbon dioxide. The multivalent cations cross-link the alginate, thereby consolidating the 3D structure and arresting the inorganic particles. In a subsequent thermal treatment the polymer is removed and the particles are sintered together. Adequate gelation requires a sufficiently low pH of the acid bath and a sufficing buffering capacity of the acid. In addition, to facilitate thermal treatment, it appears to be crucial that the acid has a conjugated base with limited propensity for complexing cations. The environmentally-safe and sustainable lactic acid and acetic acid are shown to be convenient acids. The fibers prepared via our method have outstanding properties, such as high mechanical strength, homogeneous morphology, and sharp distribution of small pores. In addition, they are prepared using sustainable chemicals such as lactic acid and calcium carbonate.

A Microfiltration Polymer‐Based Hollow‐Fiber Cathode as a Promising Advanced Material for Simultaneous Recovery of Energy and Water

“…A disadvantage of using porous flat cathodes is their low surface‐area‐to‐volume ratio. Hollow fibers with small radial dimensions provide a high surface‐area‐to‐volume ratio, combining compactness, simple and modular reactor design, and high performance . Porous inorganic hollow fibers composed of nickel and copper have been used recently as cathodes in aqueous electrolytes for proton or carbon dioxide (CO 2 ) reduction .…”

Effect of substrate curvature on microstructure and gas permeability of hollow fiber MFI zeolite membranes

“…The mechanical strength of hollow fiber substrates was found strongly dependent on the wall thickness and porosity, which, could be tailored in the preparation processes. Recently, Benes and co‐workers reported the synthesis of alumina hollow fibers with bending strengths over 200 MPa, which is much higher than typical values reported in the literature range from 100 to 150 MPa. These studies show the potential of the MFI zeolite hollow fiber membranes in industrial applications.…”

Synthesis and Characterization of Porous Ceramic Hollow Fibers with Nano-Molecular Size

“…The mixture is spun into an acidic coagulation bath, where the low pH triggers the dissociation of the carbonate into multivalent cations and carbon dioxide. [15] The objective of this research is synthesis nano alumina hollow fibers using bio-ionic gelation-internal setting method for crosslinking of sodium alginate chains by calcium ions under circumstance of acidity. Thermal treatment conditions, microstructure and surface morphology, isotherm type, and pore size distribution are studied.…”

“…Air gap was 15 mm and bore liquid flow rate was 40 Hz taken from 5 liters spinning coagulant bath of lactic acid with pH =1.60. The gels formation and the extent to which the inorganic particles are incorporated strongly depends on the pH, at this pH, a sufficient amount of calcium is released to form a stable and insoluble network [15]. The hollow fibers were left in the coagulant bath overnight.…”

“…These membranes can be used in several applications such as fabrication of solid oxide fuel cell [3], gas-liquid-solid microreaction technology [4], catalytic reactors [5,6], and porous ceramic microfiltration membranes [7,8]. Several methods have been applied for inorganic hollow fiber membranes synthesis like dry spinning [9,10], wet spinning [2], phase inversion [11][12][13], and bio-ionic gelation [14,15].…”