Edvinas Krugly

Design and characterization of electrospun polyamide nanofiber media for air filtration applications

Electrospun polyamide 6 (PA 6) and polyamide 6/6 (PA 6/6) nanofibers were produced in order to investigate their experimental characteristics with the goal of obtaining filtration relevant fiber media. The experimental design model of each PA nanofibers contained the following variables: polymer concentration, ratio of solvents, nanofiber media collection time, tip-to-collector distance, and the deposition voltage. The average diameter of the fibers, their morphology, basis weight, thickness, and resulting media solidity were investigated. Effects of each variable on the essential characteristics of PA 6/6 and PA 6 nanofiber media were studied. The comparative analysis of the obtained PA 6/6 and PA 6 nanofiber characteristics revealed that PA 6/6 had higher potential to be used in filtration applications. Based on the experimental results, the graphical representation--response surfaces--for obtaining nanofiber media with the desirable fiber diameter and basis weight characteristics were derived. Based on the modelling results the nanofiber filter media (mats) were fabricated. Filtration results revealed that nanofiber filter media electrospun from PA6/6 8% (w/vol) solutions with the smallest fiber diameters (62-66 nm) had the highest filtration efficiency (PA6/6_30 = 84.9-90.9%) and the highest quality factor (PA6/6_10 = 0.0486-0.0749 Pa-1).

PAHs in Indoor and Outdoor Air from Decentralized Heating Energy Production: Comparison of Active and Passive Sampling

Spatial and temporal variation of vapor- and particle-phase polycyclic aromatic hydrocarbons (PAHs) was determined in six urban and sub-urban locations in Kaunas, Lithuania during heating and non heating seasons. Two different sampling methodologies were used: passive (based on semipermeable membrane device, SPMD) and active (based on collection on filter and sorption). Sixteen priority PAHs as well as methylated PAHs were quantified in the collected samples. The sampled total amount of 16 PAHs investigated in SPMDs ranged from 10–138 ng/day outdoors, from 5–59 ng/day indoors during the winter sampling campaign. In summer these amounts varied from 11–19 ng/day outdoors and from 19–27 ng/day indoors. The total concentrations of vapor and particle-phase PAH in winter in actively taken samples varied from 49–286 ng/m3 outdoors and from 28–83 ng/m3 indoors. Seasonal differences as well as the influence of the fuel burning for domestic heating purposes on the PAH concentration outdoors were well reflected by the data obtained using the SPMD methodology.

Surface-deposited nanofibrous TiO 2 for photocatalytic degradation of organic pollutants

Photocatalysis is considered as an environment-friendly process able to decompose organic pollutants and increasingly applied to water and air purification. Photocatalysts having the morphology of a fibrous layer are attractive candidates for practical applications due to their high structural dimensionality and improved photocatalytic performance. This paper describes the production and characterization of supported TiO2 nanofibre layers, produced by electrospinning process and deposited on a glass plate via solvent evaporation. The obtained structures were characterized by X-ray diffraction, scanning and transmittance electron microscopies, and ellipsometry. Depending on calcination temperature, fibres contained anatase or anatase and rutile crystal phases of TiO2. The supported nanofibres formed a compact but fenestrate layer. The catalytic activity was determined by the decomposition of methylene blue and oxalic acid under UV light. The nanofibre layer proved as a competitive catalyst media based on structural properties and the degradation efficiency of several organic pollutants.Graphical abstract

Ozone-UV-catalysis based advanced oxidation process for wastewater treatment

A bench-scale advanced oxidation (AO) reactor was investigated for the degradation of six pollutants (2-naphthol, phenol, oxalic acid, phthalate, methylene blue, and d-glucose) in a model wastewater at with the aim to test opportunities for the further upscale to industrial applications. Six experimental conditions were designed to completely examine the experimental reactor, including photolysis, photocatalysis, ozonation, photolytic ozonation, catalytic ozonation, and photocatalytic ozonation. The stationary catalyst construction was made from commercially available TiO2 nanopowder by mounting it on a glass support and subsequently characterized for morphology (X-ray diffraction analysis and scanning electron microscopy) as well as durability. The ozone was generated in a dielectrical barrier discharge reactor using air as a source of oxygen. The degradation efficiency was estimated by the decrease in total organic carbon (TOC) concentration as well as toxicity using Daphnia magna, and degradation by-products by ultra-performance liquid chromatography–mass spectrometry. The photocatalytic ozonation was the most effective for the treatment of all model wastewater. The photocatalytic ozonation was most effective against ozonation and photolytic ozonation at tested pH values. A complete toxicity loss was obtained after the treatment using photocatalytic ozonation. The possible degradation pathway of the phthalate by oxidation was suggested based on aromatic ring opening reactions. The catalyst used at this experiment confirmed as a durable for continuous use with almost no loss of activity over time. The design of the reactor was found to be very effective for water treatment using photocatalytic ozonation. Such design has a high potential and can be further upscaled to industrial applications due to the simplicity and versatility of manufacturing and maintenance.

Advanced oxidation-based treatment of furniture industry wastewater

ABSTRACT The paper presents a study on the treatment of the furniture industry wastewater in a bench scale advanced oxidation reactor. The researched technology utilized a simultaneous application of ozone, ultraviolet radiation and surface-immobilized TiO2 nanoparticle catalyst. Various combinations of processes were tested, including photolysis, photocatalysis, ozonation, catalytic ozonation, photolytic ozonation and photocatalytic ozonation were tested against the efficiency of degradation. The efficiency of the processes was primarily characterized by the total organic carbon (TOC) analysis, indicating the remaining organic material in the wastewater after the treatment, while the toxicity changes in wastewater were researched by Daphnia magna toxicity tests. Photocatalytic ozonation was confirmed as the most effective combination of processes (99.3% of TOC reduction during 180 min of treatment), also being the most energy efficient (4.49–7.83 MJ/g). Photocatalytic ozonation and photolytic ozonation remained efficient across a wide range of pH (3–9), but the pH was an important factor in photocatalysis. The toxicity of wastewater depended on the duration of the treatment: half treated water was highly toxic, while fully treated water did not possess any toxicity. Our results indicate that photocatalytic ozonation has a high potential for the upscaling and application in industrial settings.

Filter media properties of mineral fibres produced by plasma spray

ABSTRACT The purpose of this study was to determine the properties of fibrous gas filtration media produced from mineral zeolite. Fibres were generated by direct current plasma spray. The paper characterizes morphology, chemical composition, geometrical structure of elementary fibres, and thermal resistance, as well as the filtration properties of fibre media. The diameter of the produced elementary fibres ranged from 0.17 to 0.90 μm and the length ranged from 0.025 to 5.1 mm. The release of fibres from the media in the air stream was noticed, but it was minimized by hot-pressing the formed fibre mats. The fibres kept their properties up to the temperature of 956°C, while further increase in temperature resulted in the filter media becoming shrunk and brittle. The filtration efficiency of the prepared filter mats ranged from 95.34% to 99.99% for aerosol particles ranging in a size between 0.03 and 10.0 μm. Unprocessed fibre media showed the highest filtration efficiency when filtering aerosol particles smaller than 0.1 µm. Hot-pressed filters were characterized by the highest quality factor values, ranging from 0.021 to 0.064 Pa−1 (average value 0.034 Pa−1).

Utilisation of Thermoplastic Polymer Waste for Nanofiber Air Filter Production

Thermoplastic polymers serving numerous practical applications are widely used in modern societies. For example, thermoplastic polystyrene is used as packaging and building insulation material, while thermoplastic nylon due to its extreme durability and strength is widely used to manufacture textile articles. However, disposal or recycling of used thermoplastic polymer items is problematic and expensive. Thermoplastic polymer waste can be successfully transformed into nano-fibres by electro-spinning. Electro-spinning is an inexpensive method where nano-fibres are generated by a charged jet of polymeric solution in a high-voltage electric field. When the jet travels in the air the solvent evaporates and charged fibres are collected on a grounded rotating drum. The diameter of nano-fibres ranges from 100 to 2000 nm and depends on the appropriate polymer solvent system, technological parameters, and environmental conditions. Due to low basis weight, large surface area to volume ratio, high pore volume, tight pore size and relatively uniform fibre size, utilised polystyrene waste could be used in nano- fibre air filters. The experimental results show that nano-fibre air filters meet High-Efficiency Particulate Air (HEPA) filtration standard, where filtration efficiency of the most penetrating particles (0.3 μm) is >85 %, and can be used to filter hazardous chemicals, biological and radioactive particles from air streams.