Particle Retention Efficiency Research Articles

Development of Cellulose Air Filters for Capturing Fine and Ultrafine Particles through the Valorization of Banana Cultivation Biomass Waste

Outdoor and indoor atmospheric pollution is one of the major problems that humanity continues to face. As a mitigation pathway, numerous technologies have been developed for air purification, including the use of fibrous filters. In this study, the particle capture efficiencies and pressure drops of air filters manufactured with cellulose pulp extracted from banana pseudostems were studied across three particle size ranges (PM10, PM2.5, and PM1). Two pretreatments were applied, alkaline with soda-antraquinone (alkali-treated pulp) and a subsequent bleaching process (bleached pulp), and four manufacturing processes were tested: crushing, freeze-drying, vacuum filtration, and pressing. In addition, a study varying filter grammage (70, 100, and 160 g·m−2) and pressing pressures (2, 4, 6, and 8 t) was also performed. After conducting these particle tests, the filter manufactured with bleached pulp, having a grammage of 160 g·m−2 and pressed at 4 t, was deemed the optimal individual solution. It demonstrated high particle retention efficiencies across all particle size ranges (with values exceeding 80%), a moderate pressure drop below 1000 Pa, and high thermal stability (degradation above 220 °C). However, combining freeze-drying and two-ton pressing processes yielded improved results (83% for the smallest particles and 89% for others) with approximately half the pressure drop. Based on these results, this study stands as a noteworthy contribution to waste valorization and the advancement of environmentally friendly materials for particle air filters. This is achieved through the adoption of simple and cost-effective technology, coupled with the utilization of 100% natural agricultural waste as the primary manufacturing material.

Food acquisition by the intertidal filter feeder bivalve Perumytilus purpuratus: Can the gill explain a differential performance between smaller individuals and the larger ones?

The intertidal zone represents a challenging environment for filter-feeding marine invertebrates. Smaller individuals are more prone to intertidal stressors than their larger conspecific; thus, reaching refuge sizes is crucial for their survival. There is no clear consensus about the morphological adaptations that small filter-feeding individuals may use to compensate for its greater mass-specific metabolic requirement relative to that of a larger conspecific. Food acquisition in filter-feedings is not only determined by the gill size but also by the efficiency of particle retention and transport rate; trade-offs between these variables may explain why smaller individuals are more efficient at acquiring energy. In this study, we examined the mechanisms underlying feeding responses in relation to body size in the intertidal suspension-feeding bivalve Perumytilus purpuratus. Clearance rate, flow rate, particle transport rate, and gill cilia development were compared over a range of sizes (7–35 mm shell length). Our results showed that small individuals possess a gill activity that makes them more efficient at collecting and transporting food particles than their larger conspecifics. Water flow rate, clearance rate, and particle transportation throughout the gill were higher per standardized gill area in smaller than larger individuals. Although the gill filaments are not all fully developed in smaller individuals, the old filaments are functional in capturing and transporting particles, which makes them more efficient per gill area than larger specimens. Taken together, we demonstrated that juveniles of P. purpuratus are more efficient than their adult conspecifics in terms of feeding capacity.

Characterizing accumulation and negative effects of aerosol particles on the leaves of urban trees

Urban vegetation can alleviate particulate matter (PM) pollution. Many studies examined the PM retention efficiencies of different plant species, but the PM changes retained on leaf surfaces and their effects on plant leaves have rarely been explored. In this study, two common urban greening tree species of the Yangtze River Delta (i.e., Broussonetia papyrifera and Osmanthus fragrans) were selected to explore the compositions of retained PM and assess their adverse impacts on leaf functional traits. Compared with B. papyrifera, O. fragrans with higher wax content was more efficient in particle accumulation, specifically fine (Φ ≤ 2.5 μm) and coarse (2.5 < Φ ≤ 10 μm) particles. The number density and mass concentration of retained PM on plant leaves tended to increase during the accumulation period. Plant species and accumulation time were two major factors to influence particle retention efficiency. Interestingly, the accumulation of particle retention influenced leaf functional traits, such as photosynthesis rate, stomatal conductance, and transpiration rate. The microscopic observations of PM on leaves confirmed that the toxic components of the retained particles potentially caused leaf injury and stomatal damage. Therefore, the acclimation mechanisms of plants responding to the retained urban aerosols should be paid attention in highly polluted areas.

Euler-Euler CFD simulation of high velocity gas injection at pool scrubbing conditions

Pressure relief by blowdown is one of the most important measures to prevent excessive pressures in the primary circuit or containment in severe nuclear accidents. Pool scrubbing can significantly reduce the release of radioactive materials, e.g., aerosols, to the environment during the pressure relief. The decontamination factor indicating the particle retention efficiency depends, among other factors, on the hydrodynamic conditions of the gas-liquid two-phase flow inside the pool. In the present work, the hydrodynamics in two typical pool scrubbing experiments is investigated with the two-fluid model, and the influence of some key factors including bubble diameter, nozzle submergence as well as interaction models are analysed. One case is a rectangular pool and the other is a cylindrical column, and their injection Weber number is around 2×103 and 4×105, respectively. The numerical results show that as the distance from the nozzle exit increases, the void fraction and velocity field expand from the central region, where the nozzle is located, to the whole cross section. The profile and its development depends largely on the bubble size and the interaction force model. It reveals that in the monodisperse simulation, the tuning of bubble diameter is necessary for achieving good agreement, although it is difficult for high velocity gas injection. More information is required to properly describe the bubble size distribution as well as its evolution in pool scrubbing conditions. Furthermore, the experimental data show clear drag reduction in the bubble swarm generated by the gas jet, and the mechanism and model improvement possibilities need to be investigated.

Numerical study of the filtering barriers influence to contain aerated particulate systems

Since the high rate of viral proliferation caused by Covid-19, it was observed that microdroplets with a pathogenic load can remain floating when in confined environments due to their low densities. They are also subject to being transported very easily when in open environments, becoming potential agents of infection. It has motivated several researchers in the field of particulate systems to try understand how particles behave in more extreme conditions. Bearing in mind that the materials currently used have a low retention yield for liquid droplets, and that protection barriers against pathogens are present both in daily use in hospital application, from diagnosis to treatment, this work simulated computationally, in a Eulerian-Eulerian approach, fluid particle retention efficiency in filter films. The simulated results indicated the high degree of retention of the filtering medium and the dependence of its saturation on the particle diameter and flow velocity, in which the greater the initial flow velocity and larger particles, the faster the saturation and detachment of particles, reducing the filter medium containment capacity. However, the results indicated that even so, retainer materials are efficient in reducing the proliferation of pathogenic loads.

The Control of Metabolic CO2 in Public Transport as a Strategy to Reduce the Transmission of Respiratory Infectious Diseases.

The global acceptance of the SARS-CoV-2 airborne transmission led to prevention measures based on quality control and air renewal. Among them, carbon dioxide (CO2) measurement has positioned itself as a cost-efficiency, reliable, and straightforward method to assess indoor air renewal indirectly. Through the control of CO2, it is possible to implement and validate the effectiveness of prevention measures to reduce the risk of contagion of respiratory diseases by aerosols. Thanks to the method scalability, CO2 measurement has become the gold standard for diagnosing air quality in shared spaces. Even though collective transport is considered one of the environments with the highest rate of COVID-19 propagation, little research has been done where the air inside vehicles is analyzed. This work explores the generation and accumulation of metabolic CO2 in a tramway (Zaragoza, Spain) operation. Importantly, we propose to use the indicator ppm/person as a basis for comparing environments under different conditions. Our study concludes with an experimental evaluation of the benefit of modifying some parameters of the Heating–Ventilation–Air conditioning (HVAC) system. The study of the particle retention efficiency of the implemented filters shows a poor air cleaning performance that, at present, can be counteracted by opening windows. Seeking a post-pandemic scenario, it will be crucial to seek strategies to improve air quality in public transport to prevent the transmission of infectious diseases.

Size exclusion and affinity-based removal of nanoparticles with electrospun cellulose acetate membranes infused with functionalized cellulose nanocrystals

Membrane filtration and affinity-based adsorption are the two most used strategies in separation technologies. Here, µm-thick multifunctional and sustainable composite membranes of electrospun cellulose acetate (CA) infused with functionalized, anionic, and cationic cellulose nanocrystals (CNCs) with enhanced wettability, tensile strength, and excellent retention capacities were designed. CNCs could uniformly impregnate into the three-dimensional CA network to effectively improve its properties. The impregnation of cationic CNCs at 0.5 wt% concentration drastically increased the tensile strength (1669%) while maintaining high permeation flux of 9400 Lm-2h−1 which is remarkable with cellulose modified electrospun membranes. The membranes infused with anionic CNCs exhibited a particle retention efficiency of 96% for 500 nm and 77% for 100 nm latex beads whilst the cationic CNC membranes exhibited a combined particle retention strategy using selectivity and size exclusion with a retention of >81% with 100 nm latex beads and 80% with ∼50 nm silver nanoparticles. We envision that the developed multifunctional membranes can be utilized for affinity-based and size-exclusion filtration to selectively trap bacteria or substances of biological significance.

Particle Retention Capacity, Efficiency, and Mechanism of Selected Plant Species: Implications for Urban Planting for Improving Urban Air Quality.

Atmospheric particulate matter (PM) has been of concern owing to its negative effects on human health and its role in environmental degradation. For mitigation purposes, it is important to select the most efficient plant species in urban greening. Here, a fast, cost-saving methodology was first added to the conventional method to investigate the size-resolved PM retention capacity and efficiency of twenty plant species. Surface PM (SPM), which can be removed by water and brushing, accounted for 44.9–66.9% of total PM, in which the water-soluble PM (DPM) accounted for 12.9–22.1% of total PM. A large mass proportion of in-wax PM (14.1–31.7%) was also observed. Platycladus orientalis, Eriobotrya japonica, Viburnum odoratissimum, Magnolia grandiflora had the highest AEleaf (retention efficiency on per unit leaf area) to retain SPM within different diameter classes (DPM, PM0.1–2.5, PM2.5–10, PM>10). AEplant (retention efficiency of individual tree) varied greatly among different plant species, mainly due to the dependence on the total area of a tree. AEland (retention efficiency on per unit green area) is a suitable index for PM retention ability and efficiency. In general, P. orientalis, V. odoratissimum, Pittosporum tobira, Photinia serrulate, M. grandiflora, E. japonica were the efficient species in retaining PM at different scales (i.e., leaf, individual tree, green area). The species like Trifolium repens, Phyllostachys viridis, were the least efficient plant species. The investigated species are all evergreen species, which will remove PM throughout the whole year, even in winter. So, we recommended that the plant species with the highest PM retention efficiency can be used in urban greening. Meanwhile, horticulture practices should also be considered to improve the leaf area index to improve their PM retention and air purification abilities.

A novel simulation approach for particulate flows during filtration

AbstractThis paper presents a novel approach for simulation of filtration process when velocity gradient within pore space cannot be neglected. The new model is useful for accurate prediction of the filtration performance and particle retention efficiency. Artificial porous media such as filters, by design, have a large surface‐to‐volume ratio because of an inherent homogeneity present within their structure; the homogenous structure is realized due to organized packing of grains as building blocks, which leads to a significant velocity gradient inner pore space. In this work, the inner‐pore flow characteristics of two different homogeneous packing patterns (cubic and oblique hexagonal packing) were examined. The multiple constricted tubes analogy was adopted to model porous media to simplify the inner‐pore geometrical structure. A new integrated simulation approach was utilized through implementing the particle trajectory model to every unit bed element of the simulation domain. The accuracy of the numerical simulations used in this study was verified by comparing the particle distribution pattern and penetration depth obtained from simulations to those monitored via a visual experiment. A sensitivity analysis was carried out to study parameters that may affect the particle distribution and penetration length, such as grain‐to‐particle size ratio, flow rate, and fluid viscosity. The simulation method utilized in this paper provides an in‐depth understanding of the fine particle migration during filtration process through artificial porous media, and, thus, provide useful insights for improved filtration design.

An investigation of calcium carbonate core-shell particles for incorporation of 225Ac and sequester of daughter radionuclides: in vitro and in vivo studies

Alpha therapy provides an outstanding prospect in the treatment of recalcitrant and micrometastatic cancers. However, side effects on the normal tissues and organs (especially, kidneys) due to the release of daughter isotopes from α-emitters remain a bottleneck. In this work, calcium carbonate core-shell particles of different sizes were considered as isotope carriers for encapsulation of 225Ac (highly powerful alpha-emitter that generates 4 net alpha particle isotopes in a short decay chain) in order to achieve in vitro and in vivo retention of 225Ac and its daughter isotopes. According to the in vitro studies, the developed calcium carbonate core-shell particles were able to retain 225Ac and its daughter isotopes (221Fr and 213Bi) exhibited good stability in biological media and dose-dependent biocompatibility (over 30 d). The SPECT imaging demonstrated the size-dependent distribution of 225Ac-doped core-shell particles. Further, in vivo studies confirmed the high retention efficiency of calcium carbonate core-shell particles, which was demonstrated in normal Wistar rats (up to 10 d). Interestingly, the radioactivity accumulation in kidney and urine was significantly less for encapsulated 225Ac than in case of non-encapsulated form of 225Ac (225Ac conjugated with albumin), indicating the absence of radioisotope leakage from the developed particles. Thus, our study validates the application of 225Ac-doped core-shell particles to sequester α-emitter (225Ac) and its decay products in order to reduce their systemic toxicity during alpha therapy.

The locally resolved filtration process for removal of phosphorus and micropollutants with GAC

Flocculation filtration in deep bed is one of the techniques to achieve advanced phosphorus removal. In addition to particle retention and phosphorus removal, granular activated carbon may serve as a filtration medium but also as an adsorption bed for micropollutants. The aim of the study was to investigate the simultaneous elimination of total phosphorus (TP) and selected micropollutants. In the first part of the study the target phosphorus threshold of 0.2 mg/L TP in the filtrate was achieved in a dual-bed media filter with anthracite and sand up to filter velocities of 16 m/h. By using a detailed sampling protocol and headloss curves, the influence of different operation modes on retention could be identified. Afterwards, the filter media were replaced by three types of GAC. In all filter beds substantial differences were found in the mode and efficiency of particle retention. This led to different filter run times, which is one of the main parameters for efficient and economical filter operation. Specific curves were generated for the different bed materials showing the dependency of filter run time on the specific load of suspended solids. Elimination of micropollutants in a GAC 4 × 8 mesh filter bed was low due to coarse grains and low empty bed contact time (EBCT). The application of GAC 8 × 14 mesh filter bed resulted in high elimination of most micropollutants. These results can be applied when choosing filter bed material. This may involve a compromise between filter run time and adsorption of micropollutants.

ISO 21083 – new international standard for determination of nanoparticles filtration efficienc

The new international standard ISO 21083 provides a method of testing filter media during the filtration of spherical shaped nanoparticles. The described procedure can be used to determine operating parameters of filtration materials of any classes. The filtration efficiency is determined on the basis of averaged results obtained for samples of the tested material in the initial state and after neutralization of the charge in the 2-propanol vapour. The standard does not introduce a division into filter classes, and in the final report of the tests, fractional particle retention efficiencies are given. This article discusses the problems of occupational safety and health, which are covered by health sciences and environmental engineering.

Nanoparticle aerosols filtration using nonwoven filter media – separation mechanisms and experimental results

This paper presents the mechanisms of nanoparticles retention on nonwoven filter media during depth aerosol filtration and the influence of parameters such as particle size, linear velocity and gas temperature, fibre diameter and packing density and surface charge of particles and fibres on retention efficiency of particles according to the classic filtration theory. Based on a review of literature sources, a comparison of filtration efficiency results obtained on the basis of classic filtration theory and experimental results is presented.

Application of density tracers in a dense medium circuit: A case study

Density tracers are often used to identify the separation efficiency of mineral processing equipment and the overall plant performance in several mineral and coal applications. In a 700 t/h coal washing plant in Turkey, comprising dense medium drums and dense medium cyclones, a plant audit was conducted using density tracers. In this study, the data obtained from the dense medium cyclone and drum circuits during the plant survey are presented. Besides the detailed separation behavior of the particles in the drums and cyclones, some variables affecting the performance such as particle retention, separation cut-point and separation efficiency are also discussed. Based on the efficiency data from the plant audit, the mass balance of the plant was obtained using an in-house-developed coal washing plant simulator (LAVE) by using the size-by-size washability data of the run-of-mine (ROM) coal and the plant control room data.

High-Flow-Rate Impinger for the Study of Concentration, Viability, Metabolic Activity, and Ice-Nucleation Activity of Airborne Bacteria.

The study of airborne bacteria relies on a sampling strategy that preserves their integrity and in situ physiological state, e.g. viability, cultivability, metabolic activity, and ice-nucleation activity. Because ambient air harbors low concentrations of bacteria, an effective bioaerosol sampler should have a high sampling efficiency and a high airflow. We characterize a high-flow-rate impinger with respect to particle collection and retention efficiencies in the range 0.5-3.0 μm, and we investigated its ability to preserve the physiological state of selected bacterial species and seawater bacterial community in comparison with four commercial bioaerosol samplers. The collection efficiency increased with particle size and the cutoff diameter was between 0.5 and 1 μm. During sampling periods of 120-300 min, the impinger retained the cultivability, metabolic activity, viability, and ice-nucleation activity of investigated bacteria. Field studies in semiurban, high-altitude, and polar environments included periods of low bacterial air concentrations, thus demonstrating the benefits of the impinger's high flow rate. In conclusion, the impinger described here has many advantages compared with other bioaerosol samplers currently on the market: a potential for long sampling time, a high flow rate, a high sampling and retention efficiency, low costs, and applicability for diverse downstream microbiological and molecular analyses.

Potential methodological influences on the determination of particle retention efficiency by suspension feeders: Mytilus edulis and Ciona intestinalis

The retention efficiency (RE) of suspension-feeding bivalve molluscs depends on par- ticle size and is generally assumed to decline below a maximum retention of particles larger than 3 to 7 μm. Previous suggestions that the RE spectrum of mussels Mytilus edulis can exhibit variability, possibly as a result of physiological regulation, have been attributed to artifacts associated with the indirect method. The possibility that variable physical properties of seston particles and/or miscal- culations can result in inaccurate RE measurements was examined using 3 methodologies (static, flow-through and a new approach based on the static method) and 3 particle sources (natural seston, algal cell monocultures and clay). Measurements obtained with the static method varied de- pending on the selected sampling interval. However, this artifact can be removed using frequent sampling and a regression analysis approach. Accurate RE measurements can be obtained with the flow-through method when feeding behaviour is flow independent. For all particle suspensions and methods, mussels from the study site in Lysefjord, Norway, had a maximum RE for particles >8-11 μm (1 to 5 September 2015). The RE for smaller particles declined gradually, with 50-60% retention of 4 μm particles and 30-40% retention of 2 μm particles. Differences in the RE size spectra of mussels and tunicates Ciona intestinalis, collected and measured at the same site, further indicated that RE was not influenced by potentially confounding methodological factors. Assump- tions regarding the RE spectrum of bi valves have contributed to many conclusions on their ecosys- tem interactions. The reliability of clearance rate measurements obtained using the indirect method can only be assured if the effective retention of tracer particles is confirmed and not assumed.

Ultrasonic based investigation on particle size distribution and retention efficiency of particulate matters retained on tree leaves&amp;mdash;Taking Ginkgo biloba and Pinus tabuliformis as examples

Ultrasonic based investigation on particle size distribution and retention efficiency of particulate matters retained on tree leaves&amp;mdash;Taking Ginkgo biloba and Pinus tabuliformis as examples

Fabrication of paper-based devices by lacquer spraying method for the determination of nickel (II) ion in waste water

A spraying method with lacquer was developed for the fabrication of paper-based devices. A patterned iron mask was initially placed on a filter paper and held tightly attached by a magnetic plate placed on the opposite side. After that, acrylic lacquer was sprayed on the filter paper to create a hydrophobic area while the hydrophilic area was protected with the iron mask. The optimal conditions for the fabrication of this device were studied including lacquer type and particle retention efficiency of filter paper. Gloss spray lacquer and filter paper No. 4 were chosen as optimal lacquer type and particle retention efficiency of filter paper, respectively. To evaluate its efficiency, the paper-based devices were used to determine nickel using electrochemical detection. Cu-enhancer solution was employed to increase sensitivity of nickel determination with the optimal concentration of 4.5ppm. Under the optimal conditions, linear range was observed in the range of 1–50ppm with a coefficient of determination of 0.9971. The limit of detection (LOD) and the limit of quantitation (LOQ) were found to be 0.5 and 1.97ppm, respectively. Moreover, these paper-based devices coupled with electrochemical detection were applied to determine nickel in waste water of a jewelry factory and compared to those obtained with inductively coupled plasma optical emission spectrometry (ICP-OES). The results indicated that there were no significant variations between this proposed method (4.15±0.043ppm) and the ICP-OES method (4.06±0.013ppm). Therefore, this spraying method was found to be an excellent alternative for the fabrication of paper-based devices due to its ease of use, affordability and simplicity.

Discrete phase modeling study for particle motion in storm water retention

This study compares three different types of multiple phase models to determine the most appropriate one for predicting the behavior of various types of storm water solids in a rectangular retention chamber. Two Lagrangian frame of coupled and uncoupled particle tracking models based on the interaction between the discrete phase and the continuous phase were tested. The third model was a sediment transport model using the Eulerian frame. This study tested five different storm water solids classified by particle size and settling characteristics. Particle retention efficiency and computational time were considered in determining the most appropriate multiphase model. For the gross solids, the Lagrangian coupled model provided the best agreement with the physical model measurements. The Eulerian frame model matched retention efficiency well for the high density coarse and finer solids. Although the Eulerian frame shows reliable retention prediction for most of the solid types, the Lagrangian coupled model can be an effective alternative requiring significantly reduced computational time.

Variability in particle retention efficiency by the mussel Mytilus edulis

Seasonal variation in blue mussel, Mytilus edulis, retention efficiency ( RE) responses to natural seston concentrations were investigated in the Lysefjord, Norway. The smallest particles shown to be effectively retained (100%) were approximately 7 μm and this was observed on only one occasion. The most common response was for RE to progressively increase from small to large particles with maximum RE at 30 to 35 μm (8 of 12 experiments). Temporal changes in the seston size distribution towards a dominance of smaller particles coincided with a decrease in the RE maxima to particles between 7 and 15 μm diameter. The RE of 1 μm and 4 μm diameter particles ranged between 14–64% and 12–86%, respectively, showing that small particles occasionally serve as a significant dietary component. The observed temporal variations in particle capture suggest a capacity of M. edulis to control particle retention mechanisms based on exogenous dietary cues that are directly or indirectly related to the ambient particle size distribution. Indirect clearance rate ( CR) measurements require that all particle sizes under study are effectively retained and this has widely been assumed for particles larger than 4 μm. CR was calculated for particles ranging in size from 5 to 35 μm and the percentage reduction in CR, relative to particle sizes shown to be effectively retained, ranged from 11% to 87%. CR calculations that included all particle counts between 5 and 35 μm diameter were underestimated by a mean of 26% (0–48% range). Similar errors in diet characterization may be expected to affect particle selection and absorption efficiency measurements and the compounding of errors may become extreme when a number of physiological rates and efficiencies are integrated (e.g. scope for growth).