SI Filters Research Articles

A reference methodology for microplastic particle size distribution analysis: Sampling, filtration, and detection by optical microscopy and image processing

AbstractMicroplastic (MP) contamination in natural water circulation is a concern for environmental issues and human health. Various types of polymer materials have been identified and were detected in MP analytic test procedures. Beyond MP polymer type, particle size and form play a major role in water analysis due to possible negative toxicologic effects on flora and fauna. However, the correct quantitative measurement of MP size distribution over several orders of magnitude is strongly influenced by sample preparation, filtration materials and processes, and microanalytical techniques, as well as data acquisition and analysis. In this paper, a reference methodology is presented aiming at an improved quantitative analysis of MP particles. An MP analysis workflow is demonstrated including all steps from reference materials to sample preparation, filtration handling, and MP particle size distribution analysis. Background‐corrected particle size distributions (1–1000 µm) have been determined for defined polyethylene (PE) and polyethylene terephthalate (PET) reference samples. Microscopically measured particle numbers and errors have been cross‐checked with the total initial mass. In particular, defined reference MP samples (PE, PET) are initially characterized and applied to filtration experiments. Optical microscopy imaging on full‐area Si filters with subsequent image analysis algorithms is used for statistical particle size distribution analysis. To quantify the effects of handling and filtration, several blind tests with distilled water are carried out to determine the particle background for data evaluation. Particle size distributions of PE and PET reference samples are qualitatively and quantitatively reproduced with respect to symmetry, and maximum and cut‐off diameter of the distribution. It is shown that especially MP particles with a radius of >50 µm can be detected and retrieved with high reliability. For particle sizes <50 µm, a significant interference with background contamination is observed. Data from blank samples allows a correction of background contaminations. Furthermore, for enhanced sampling statistics, the recovery of the initial amount of MP will be qualitatively shown. The results are intended as an initial benchmark for MP analytics quality. This quality is based on statistical MP particle distributions and covers the complete analytic workflow starting from sample preparation to filtration and detection. Microscopic particle analysis provides an important supplement for the evaluation of established spectroscopic methods such as Fourier‐transform infrared spectroscopy or Raman spectroscopy.

Cascade filter system tests for airborne nano‐ and microplastic particle analytics in a laboratory dust chamber

AbstractMeasuring nano‐ and microplastic particle (NMP) loads in air requires suitable analytical filter systems that allow a size‐selective separation of airborne nano‐ and microplastic (NMP) fractions. Previously, various filter materials and setups including nano/micro cascade filtration stacks have been presented (P.‐T. Miclea, 2022). To evaluate these novel filter systems, implementing reliable sampling procedures and instrumentation, as well as sample handling, well‐defined test setups, NMP reference materials, and procedures are of major interest. In this study, a novel triple‐stage silicon (Si) and aluminum oxide (Al2O3) cascade filter system for airborne NMP particles is tested in a laboratory environment. Special focus is put on its ability for size‐selective analytical filtration of airborne NMP particles based on a well‐defined mixture of poly‐ and monodisperse NMP reference materials. For this purpose, a laboratory dust test chamber has been adapted for the dispersion of NMP particles in air as well as the vacuum air extraction through the cascade filter system. A defined NMP test material was fabricated from polydisperse polyethylene (PE) and PE terephthalate, and monodisperse polystyrene, polymethylmethacrylate, spanning a size region from 130 nm to >22 µm. Dispersion and filtration experiments are performed by vacuum extraction under defined temperature, pressure, and humidity conditions on single and triple filtration stages. NMP particle analytics are performed with polydisperse PE particles on a single‐stage filter system with subsequent optical microscopy. Here, the aim is to detect the filtration cutoff for retained particles and transmitted particles referring to initial distribution. A second experiment is run on a triple filtration cascade with mixed poly‐ and monodisperse NMP test material. The different filter stages are equipped with analytical Si and Al2O3 filters with pore sizes of 10 µm, 1 µm, and 100 nm, to test the size selectivity and sealing of the complete cascade setup. The NMP particle size distribution on the individual analytical filter substrates is analyzed by optical and scanning electron microscopy to assess size selectivity performance of the triple‐stage setup. The obtained results in our laboratory NMP dust‐dispersion test chamber demonstrate requirements and limitation of size‐selective NMP cascade filter systems and the involved analytical procedures. Future applications in real indoor and outdoor environments will be discussed.

Note: Thermally stable thin-film filters for high-power extreme-ultraviolet applications.

We investigated several types of thin-film filters for high intensity work in the extreme-ultraviolet (EUV) spectral range. In our application, with a peak EUV intensity of 2.7 W cm(-2), Ni-mesh-backed Zr filters have a typical lifetime of 20 h, at which point they suffer from pinholes and a 50% loss of transmission. Initial trials with Si filters on Ni meshes resulted in rupture of the filters in less than an hour. A simple thermal calculation showed that the temperature rise in those filters to be about 634 K. A similar calculation indicated that using a finer mesh with thicker wires and made of Cu reduces the temperature increase to about 60 K. We have exposed a Si filter backed by such a mesh for more than 60 h with little loss of transmission and no leaks.

A new extended soft intersection set to (M, N)-SI implicative fitters of BL-algebras.

Molodtsov's soft set theory provides a general mathematical framework for dealing with uncertainty. The concepts of (M, N)-SI implicative (Boolean) filters of BL-algebras are introduced. Some good examples are explored. The relationships between (M, N)-SI filters and (M, N)-SI implicative filters are discussed. Some properties of (M, N)-SI implicative (Boolean) filters are investigated. In particular, we show that (M, N)-SI implicative filters and (M, N)-SI Boolean filters are equivalent.

(M, N)-soft intersection BL-algebras and their congruences.

The purpose of this paper is to give a foundation for providing a new soft algebraic tool in considering many problems containing uncertainties. In order to provide these new soft algebraic structures, we discuss a new soft set-(M, N)-soft intersection set, which is a generalization of soft intersection sets. We introduce the concepts of (M, N)-SI filters of BL-algebras and establish some characterizations. Especially, (M, N)-soft congruences in BL-algebras are concerned.