Mixed Matrix Poly(Vinyl Alcohol)-Copper Nanofibrous Anti-Microbial Air-Microfilters

Abstract

Membranes decorated with biocide materials have shown great potential for air sanitization but can suffer from biocide agent leaching by dissolution in water. In order to tackle the diffusion of biocide metal ions from the fiber matrix, composite nanofiber membranes of poly(vinyl alcohol) (PVA) cross-linked with copper (II) acetate have been successfully engineered via sol–gel electrospinning, providing a stable mean for air bactericidal microfiltration. The novelty lies in the bonding strength and homogeneous distribution of the fiber surface biocide, where biocide metals are incorporated as a sol within a polymer matrix. The electrospinning of bead-free composite nanofibers offered over 99.5% filtration efficiency for PM2.5, with a theoretical permeance above 98%. The PVA/copper nanofiber membranes also showed satisfactory anti-bacterial performance against the gram-negative Escherichia coli within 24 h, making them promising materials for the remediation of airborne bacteria. The mechanical and chemical stability of the engineered nanocomposite electrospun nanofiber webs added to the natural biodegradability of the materials, by offering ideal low-cost sanitary solutions for the application of air disinfection in both indoor and outdoor fitting a circular economy strategy where advanced materials are redesigned to be sustainable.

Review on Polymeric, Inorganic, and Composite Materials for Air Filters: From Processing to Properties

“…[74,75] Antimicrobial metal NPs, such as silver or copper, were successfully incorporated into the filter structure by the addition of metal nitrates or metal acetates into the electrospinning solution, followed by the photoreduction of electrospun fibers by means of ultraviolet (UV) light. [37,67,76,77] However, to avoid the increase in the conductivity within the electrospun jet due to the inclusion of a metal salt, immobilization can be performed, e.g., by means of sol-gel crosslinking. [76] Several inorganic fibers were fabricated by thermal treatment of electrospun precursors prepared from polymeric solutions.…”

“…[37,67,76,77] However, to avoid the increase in the conductivity within the electrospun jet due to the inclusion of a metal salt, immobilization can be performed, e.g., by means of sol-gel crosslinking. [76] Several inorganic fibers were fabricated by thermal treatment of electrospun precursors prepared from polymeric solutions. [78,79] Although the thermal treatment of electrospun precursors is usually carried out under ambient air to decompose organic components, inert atmospheres were also applied to preserve carbon species in the fibers.…”

“…These NPs can electrostatically interact with microorganisms, provide high surface areas for cell contact and release metal ions, during which they can disrupt cellular respiration, penetrate the cell membrane, and disrupt metabolic processes. [76,172,199] The resulting leached and dead bacteria after contacting PI/copper foam filter are shown in Figure 14b. Even when incorporated into a polymer matrix or MOFs, metal ions and organic ligands can be released from metal NPs and MOF crystals.…”

The Role of New Inorganic Materials in Composite Membranes for Water Disinfection

“…Membranes 2020, 10, x FOR PEER REVIEW 9 of 17 Different metal-based nanocomposite materials have also been developed for water disinfection. For instance, mixed matrix cross-linked PVA-Cu nanocomposite fibers have shown over 99.5% filtration efficiency in removing E. coli [68]. Certainly, copper is well known for its strong antibacterial activity; for example, it is recognized to kill 99.9% of pathogens in 2 h. Commonly, copper ions can kill bacteria on direct contact due to DNA degradation [69,70].…”

Electrically Responsive Coarse Filters Endowed by High-Dielectric-Constant Surface Coatings toward Efficient Removal of Ultrafine Particles and Ozone

“…However, high-efficiency air filters accompany a large resistance to airflow, possibly costing up to a quarter of power consumption in large commercial HVAC systems. , Additionally, as time goes by, the filter will gradually become clogged by the PM coating, so the air resistance further rises steeply . Fabricating nanofiber filters is an ideal way to reduce air resistance. − The possibility of particle capture increases due to the larger surface area of fibers on the nanometer scale, ensuring effective PM removal with a much thinner filter. Besides, lower air resistance occurs when the nanofiber diameter is comparable to or smaller than the mean free path of air molecules, thus introducing a slip effect. , However, nanofiber filters are usually made into membranes, which is not suitable for facilitation in building ventilation systems.…”