Nanofibrous Polymeric Membranes for Air Filtration Application: A Review of Progress after the COVID‐19 Pandemic

Abstract Air pollution is one of the major global problems causing around 7 million dead per year. In fact, a connection between infectious disease transmission, including COVID‐19, and air pollution has been proved: COVID‐19 consequences on human health are found to be more severe in areas characterized by high levels of particulate matter (PM). Therefore, after the COVID‐19 pandemic, the production of air filtration devices with high filtration efficiency has gained more and more attention. Herein, a review of the post‐COVID‐19 pandemic progress in nanofibrous polymeric membranes for air filtration is provided. First, a brief discussion on the different types of filtration mechanism and the key parameters of air filtration is proposed. The materials recently used for the production of nanofibrous filter membranes are presented, distinguishing between non‐biodegradable polymeric materials and biodegradable ones. Subsequently, production technique proposed for the fabrication of nanofibrous membranes, i.e., electrospinning and solution blow spinning, are presented aiming to analyze and compare filtration efficiency, pressure drop, reusability and durability of the different polymeric system processed with different techniques. Finally, present challenges and future perspectives of nanofibrous polymeric membranes for air filtration are discussed with a particular emphasis on strategies to produce greener and more performant devices

Green Composites Based on Mater-Bi^® and <i>Solanum lycopersicum</i> Plant Waste for 3D Printing Applications

3D printability of green composites is currently experiencing a boost in importance and interest, envisaging a way to valorise agricultural waste, in order to obtain affordable fillers for the preparation of biodegradable polymer-based composites with reduced cost and environmental impact, without undermining processability and mechanical performance. In this work, an innovative green composite was prepared by combining a starch-based biodegradable polymer (Mater-Bi®, MB) and a filler obtained from the lignocellulosic waste coming from Solanum lycopersicum (i.e., tomato plant) harvesting. Different processing parameters and different filler amounts were investigated, and the obtained samples were subjected to rheological, morphological, and mechanical characterizations. Regarding the adopted filler amounts, processability was found to be good, with adequate dispersion of the filler in the matrix. Mechanical performance was satisfactory, and it was found that this is significantly affected by specific process parameters such as the raster angle. The mechanical properties were compared to those predictable from the Halpin–Tsai model, finding that the prepared systems exceed the expected values

Green Composites Based on Mater-Bi® and Solanum lycopersicum Plant Waste for 3D Printing Applications

3D printability of green composites is currently experiencing a boost in importance and interest, envisaging a way to valorise agricultural waste, in order to obtain affordable fillers for the preparation of biodegradable polymer-based composites with reduced cost and environmental impact, without undermining processability and mechanical performance. In this work, an innovative green composite was prepared by combining a starch-based biodegradable polymer (Mater-Bi®, MB) and a filler obtained from the lignocellulosic waste coming from Solanum lycopersicum (i.e., tomato plant) harvesting. Different processing parameters and different filler amounts were investigated, and the obtained samples were subjected to rheological, morphological, and mechanical characterizations. Regarding the adopted filler amounts, processability was found to be good, with adequate dispersion of the filler in the matrix. Mechanical performance was satisfactory, and it was found that this is significantly affected by specific process parameters such as the raster angle. The mechanical properties were compared to those predictable from the Halpin-Tsai model, finding that the prepared systems exceed the expected values

Opuntia Ficus Indica based green composites for NPK fertilizer controlled release produced by compression molding and fused deposition modeling

Excessive fertilization causes ecological problems due to leaching issues. To solve this problem and promote agriculture sustainability an innovative green composite for controlled release fertilizers was produced by adding NPK fertilizer flour to a biodegradable polymer with or without Opuntia Ficus Indica (OFI) particles. Six for- mulations were produced and employed for the fabrication of devices both for compression molding and fused deposition modeling (FDM). Both fillers displayed a good dispersion in the composites, excellent adhesion with the polymeric matrix and effectively acted as reinforcement. The decrease of NPK release rate (up to 30 days) was achieved using whole composites prepared. By appropriately selecting the dimension of the particles, the addition of OFI and the production technique, was possible to modulate the NPK release rate: FDM samples containing fine particles of OFI and NPK displayed the fastest release. Release data were fitted according to Peppas-Korsmeyer model to understand the release mechanism

Green composites for fertilizer controlled release produced by compression molding and FDM

Excessive fertilization causes ecological problems due to leaching issues. To solve this problem and promote agriculture sustainability an innovative green composite for controlled release fertilizers was produced by adding NPK fertilizer flour to a biodegradable polymer with or without Opuntia Ficus Indica (OFI) particles. Six formulations were produced and employed for the fabrication of devices both for compression molding (CM) and fused deposition modeling (FDM). Both fillers displayed a good dispersion in the composites, excellent adhesion with the polymeric matrix and effectively acted as reinforcement. The decrease of NPK release rate (up to 30 days) was achieved using whole composites prepared. By appropriately selecting the dimension of the particles, the addition of OFI and the production technique, was possible to modulate the NPK release rate: FDM samples containing fine particles of OFI and NPK displayed the fastest release. Release data were fitted according to Peppas-Korsmeyer model to understand the release mechanism

Biodegrading biofilms on biopolymeric sorbent scaffolds

Abstract Immobilization of hydrocarbon-degrading microorganisms on biodegradable adsorbing scaffolds significantly promotes bioremediation processes in fresh and sea water . Recently low cost, ecofriendly bioremediation devices based on polycaprolactone and polylactic acid membranes hosting a biodegrading bacterial biofilm were obtained [1]. The resulting biosorbent biodegrading biofilms simultaneously adsorbed 100 % of spilled oil and biodegraded more than 66% of it over 10 days; biodegradation was 23% higher than that obtained using free living bacteria [1]. In this work, adhesion, survival and HC-biodegradation ability of these biodegrading biofilms was tested in long term experiments and under dry conditions mimicking smog-contaminated air. The HC-degrading Actinobacteria Nocardia cyriacigeorgica strain SoB, Gordonia amicalis strain SoCg [2], and the marine hydrocarbonoclastic Alcanivorax borkumensis strain AU3-AA-7 [3] were immobilized on polylactic acid (PLA) and polycaprolactone (PCL) membranes prepared by electrospinning [1]. The capacity of adhesion and proliferation of bacterial cells into the biopolymers were evaluated using scanning electron microscopy (SEM) after 5, 10, 15 and 30 days. PLA and PCL nanofibers appear almost completely covered by a complex three dimensional bacterial film for all the strains. Total biomass (estimated as total dsDNA) confirmed biofilm growth up to 30 days incubation. Viable plate counts and Gas Chromatography-FID analysis revealed that the biofilm was vital and functional after 30 days. Exposing a 15-day liquid incubated biofilms to further 15 days in a hexadecane-saturated air chamber reduced by 100fold plate count yeld. Bibliography: [1] Catania V., Lopresti F., Cappello S., Scaffaro R. and Quatrini P. (2020). N Biotechnol, 58, 25-31. [2] Quatrini P., Scaglione G., De Pasquale C., Riela S. and Puglia A.M. (2008). J. Appl. Microbiol.,104(1),251-259. [3] Catania V., Santisi S., Signa G., Vizzini S., Mazzola A., Cappello S.,. Yakimov M.M. and Quatrini P. (2015). Mar. Pollut. Bull., 99(1-2), 138-149. Acknowledgments: Elisa Maria Petta’s PhD grant is financed by PON "Research and Innovation" 2014-2020, Axis IV "Education and research for recovery" Action IV.5 "PhDs on green issues

An innovative route to prepare in situ graded crosslinked PVA graphene electrospun mats for drug release

We present a fast, one step method to obtain PVA/graphene/chlorhexidine nanofibrous membranes, with a crosslinking gradient along their cross-section. Briefly, polymeric solutions were electrospun onto a heated plate, enabling the in situ crosslinking of PVA macromolecules. Of course, the crosslinking degree of such structures was found to decrease upon the distance from the plate during deposition. The outcomes reveal the crucial role of graphene, capable of promoting heat transfer throughout the entire structure, thus leading to 70-80% crosslinking degrees and preventing delamination issues. Such membranes were compared to untreated and oven thermally treated ones, and a robust relationship between processing, structure and properties was outlined, with a special focus on the release behaviour of such materials, which proved to be tuneable from instantaneous/burst to sustained release (up to 500 hours) by adjusting formulation and preparation technique