Search Results (47)

Bamboo, a fast-growing and biodegradable industrial crop, exhibits excellent mechanical properties, which facilitate its widespread use in construction, furniture, and decorative applications. However, its inherently limited permeability hinders processing during drying, chemical modification, dyeing, and impregnation. Although previous studies have explored structural and treatment-related aspects, few have offered a comprehensive and integrative overview that bridges anatomical structure, permeation mechanisms, performance evaluation, and treatment strategies. This review synthesizes 126 publications from 1997 to 2024 to provide a comprehensive, multidimensional analysis of bamboo permeability. Structure–function relationships are examined by assessing how vessels, sieve tubes, perforation plates, pits, and bamboo nodes influence permeability, with an emphasis on quantitative correlations. Capillarity, diffusion, and viscous resistance are integrated into a unified theoretical framework, proposing a model that couples longitudinal capillary rise with transverse diffusion. Detection approaches, including both direct techniques (weight gain, microscopy, tracer elements, fluorescence imaging) and indirect techniques (porosity measurement, Micro-CT), with their respective advantages, limitations, and applications. Enhancement strategies are categorized into chemical, physical, and biological methods, with assessments of their effectiveness, environmental impact, and energy consumption. Overall, this review provides a holistic perspective on bamboo permeability and offers valuable guidance for future research and engineering applications. Full article

Odorous emissions from hot-mix asphalt (HMA) plants are a growing environmental concern, particularly due to airborne aldehydes and ketones, which have low odor thresholds and a strong sensory impact. This study presents a field-ready analytical method for monitoring odor-active volatile compounds. The system uses dynamic solid-phase microextraction (SPME and SPME Arrow) with on-fiber derivatization via O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) and is coupled to gas chromatography–mass spectrometry (GC–MS) for direct detection. A flow-cell sampling unit enables the real-time capture of aliphatic aldehydes and ketones under transient emission conditions. Calibration using permeation tubes demonstrated sensitivity (limits of detection (LODs) below 0.13 μg/m³), recovery above 85% and consistent reproducibility. Compound identity was confirmed using retention indices and fragmentation patterns. Uncertainty assessment followed ISO GUM (Guide to the Expression of Uncertainty in Measurement) standards, thereby validating the method’s environmental applicability. Field deployment 200 m from an HMA facility identified measurable concentrations that aligned with CALPUFF model predictions. The method’s dual-isomer resolution and 10 min runtime make it ideal for responding to time-sensitive odor complaints. Overall, this approach supports regulatory efforts by enabling high-throughput on-site chemical monitoring and improving source attribution in cases of odor nuisance. Full article

We present a corrosion-resistant quadrupole ion trap mass spectrometer (QIT-MS) designed for trace detection of volatiles in sulfuric acid aerosols, with a specific focus on phosphine (PH₃). Here, we detail the gas calibration methodology using permeation tube technology for generating certified ppb-level PH₃/H₂S/CO₂ mixtures, and report results from mass spectra with sufficient resolution to distinguish isotopic envelopes that validate the detection of PH₃ at a concentration of 62 ppb. Fragmentation patterns for PH₃ and H₂S agree with NIST data, and signal-to-noise performance confirms ppb sensitivity over 2.6 h acquisition periods. We further assess spectral interferences from oxygen isotopes and propose a detection scheme based on isolated phosphorus ions (P⁺) to enable specific and interference-resistant identification of PH₃ and other reduced phosphorus species of astrobiological interest in Venus-like environments. This work extends the capabilities of QIT-MS for trace gas analysis in chemically aggressive atmospheric conditions. Full article

Polyethylene terephthalate (PET) is one of the most used polymeric substances in production of packaging materials, fibers, textiles, coatings, and engineering materials. This paper elucidates the transport parameters of hydrogen gas through a PET membrane, which was selected to be a sufficiently permeable substrate for setting up an empirical strategy that aims at developing hydrogen barrier coatings. An examination of the structural degradation of PET by prolonged hydrogen exposure was performed. Hydrogen permeation tests were performed on a PET membrane with a thickness of 50 μm. To investigate the behavior of the material by prolonged hydrogen treatment, hydrogen-exposure experiments were carried out at a certain hydrogen pressure and time. Comparisons of the mechanical properties of the material were documented both before and after hydrogen exposure. A strong impact of comparatively transient hydrogen exposure on the mechanical and hydrogen transport properties of PET was observed. After 72 h of hydrogen exposure at 10³ hPa and 300 K, the tensile strength decreased by 19%, the diffusion coefficients more than doubled, and material fracture behavior changed from ductile to distinctly brittle. This underlines the importance of developing effective hydrogen barrier coatings in case PET tubing is intended for use in hydrogen transport or storage. Full article

This study aimed to evaluate the sulfur hexafluoride (SF₆) tracer technique for estimating methane (CH₄) emissions in dual-flow continuous culture systems (DFCCS). In experiment 1 (Exp1), fermenters were filled with water, and known CH₄ concentrations (0, 1.35, 2.93, or 4.43 g/d) were injected using permeation tubes with SF₆ release rates (3.30 or 9.65 mg/d). Headspace gas was collected using canisters, and the SF₆ technique estimated CH₄ recovery. Experiment 2 (Exp2) involved a DFCCS fermentation trial with ruminal fluid from three Holstein cows, testing diets with soybean meal or its partial replacement (50%) by Chlorella or Spirulina. Headspace gas was collected at intervals post-feeding. Standard curves for SF₆ and CH₄ quantification were inadequate for DFCCS samples, with the CH₄:SF₆ ratio differing from standards, indicating the data needs further SF₆ release rate evaluation. In Exp1, a high correlation (r = 0.97) was found between infused and calculated CH₄, indicating good repeatability. Low and high SF₆ rates performed similarly at low CH₄ infusion, but high SF₆ overestimated CH₄ at high infusion. Exp2 showed CH₄ emissions irrespective of SF₆ rate and indicated reduced CH₄ emissions and increased NDF degradation with algae-containing diets. Further evaluation of the SF₆ tracer technique is warranted for DFCCS. Full article

The time-lag method is commonly used to determine membrane permeability, diffusivity and solubility in a single gas permeation experiment in a constant volume system. An unwritten assumption on which this method relies is that there is no resistance to gas accumulation in the downstream receiver of the system. However, this is not the case, even with the specially designed receiver used in this study when, in addition to tubing, the receiver utilizes an additional accumulation tank. The resistance to gas accumulation originates from a finite diffusivity (Knudsen diffusion) of gases in tubing, which are magnified by “resistance-free” accumulation tank(s). As a result of the resistance to gas accumulation, the time lag of the membrane is underestimated, which leads to an overestimation of gas diffusivity in the membrane. The experimentally predicted resistances in different configurations of the receiver, expressed by the difference in the time lag at two different receiver locations, were several times greater than the theoretically predicted values. A high molecular PPO membrane was used to demonstrate this effect. The time lags measured at different locations differed by as much as 30%. The diffusivity of nitrogen in a PPO of 4.04 × 10⁻¹² m²/s determined at the optimum configuration of the receiver is at least 50% lower than the literature-reported values. Full article

Hydrogen permeation sparked a renewed interest in the second half of the 20th century due to the favorable features of this element as an energy factor. Furthermore, niche applications such as nuclear fusion gained attention for the highest selectivity ensured by self-supported dense metallic membranes, especially those consisting of Pd-based alloys. In this framework, the ENEA Frascati laboratories have decades of experience in the manufacturing, integration, and operation of Pd-Ag permeators. Most of the experimental investigations were performed on single-tube membranes, proving their performance under relevant operational conditions. Nowadays, once the applicability of this technology has been demonstrated, the scalability of the single-tube experience over medium- and large-scale units must be verified. To do this, ENEA Frascati laboratories have designed and constructed a multi-tube permeator, namely the Medium-Scaled Membrane Reactor (MeSMeR), focused on scalability assessment. In this work, the results obtained with the MeSMeR facility have been compared with previous experimental campaigns conducted on single-tube units, and the scalability of the permeation results has been proven. Moreover, post-test simulations have been performed based on single-tube finite element modeling, proving the scalability of the numerical outcomes and the possibility of using this tool for scale-up design procedures. Full article

The recovery and recycling of metals that generate toxic ions in the environment is of particular importance, especially when these are tungsten and, in particular, thorium. The radioactive element thorium has unexpectedly accessible domestic applications (filaments of light bulbs and electronic tubes, welding electrodes, and working alloys containing aluminum and magnesium), which lead to its appearance in electrical and electronic waste from municipal waste management platforms. The current paper proposes the simultaneous recovery of waste containing tungsten and thorium from welding electrodes. Simultaneous recovery is achieved by applying a hybrid membrane electrolysis technology coupled with nanofiltration. An electrolysis cell with sulphonated polyether–ether–ketone membranes (sPEEK) and a nanofiltration module with chitosan–polypropylene membranes (C–PHF–M) are used to carry out the hybrid process. The analysis of welding electrodes led to a composition of W (tungsten) 89.4%; Th 7.1%; O₂ 2.5%; and Al 1.1%. Thus, the parameters of the electrolysis process were chosen according to the speciation of the three metals suggested by the superimposed Pourbaix diagrams. At a constant potential of 20.0 V and an electrolysis current of 1.0 A, the pH is varied and the possible composition of the solution in the anodic workspace is analyzed. Favorable conditions for both electrolysis and nanofiltration were obtained at pH from 6 to 9, when the soluble tungstate ion, the aluminum hydroxide, and solid thorium dioxide were formed. Through the first nanofiltration, the tungstate ion is obtained in the permeate, and thorium dioxide and aluminum hydroxide in the concentrate. By adding a pH 13 solution over the two precipitates, the aluminum is solubilized as sodium aluminate, which will be found after the second nanofiltration in the permeate, with the thorium dioxide remaining integrally (within an error of ±0.1 ppm) on the C–PHF–M membrane. Full article

This work theoretically studies the capability of using vortex tubes to provide the necessary heating and cooling energies required by a typical direct-contact membrane distillation (MD) process. The vortex tube generates a temperature separation that can supply the membrane distillation process with sufficiently hot feed and cold permeate with a temperature difference as large as 70 °C. Several structures integrating vortex tubes and MD with and without heat recovery and cascading are proposed and their respective performances are assessed and compared. A maximum distillate production of 38.5 kg/h was obtained at an inlet air pressure of 9 bar, cold air mass ratio of 0.7, and air-to-water mass ratio of 9. The corresponding energy consumption was found to be 25.9 kWh/m³. The production rate can be increased up to 75.2 kg/h and the specific energy consumption can be reduced to 13.3 kWh/m³ when three MD stages were connected in series using the same single vortex tube at the same operating conditions. It is found that the cold fraction plays an important role in the balance between heating and cooling operations. In addition, cold fraction values smaller than 0.7 should be avoided to prevent water from freezing inside the membrane. Full article

The Permeator Against Vacuum (PAV) is one of the proposed technologies for the Tritium Extraction System of the WCLL BB (Water-Cooled Lithium-Lead Breeding Blanket) of the EU DEMO reactor. In this paper, the manufacturing of the first PAV mock-up with a niobium membrane with a cylindrical configuration is presented. This work aimed to demonstrate the possibility of manufacturing a relevant-size PAV to be later tested in the TRIEX-II facility. The adopted prototypical solutions are described in detail, starting with the methodology developed to join the Nb tubes with a 10CrMo9-10 (A182 F22) plate. Dedicated manufacturing and welding procedures, based on vacuum brazing with a nickel-based brazing alloy, were developed to solve the problem. This new kind of brazing was first analyzed to check the morphology of the joint and then tested to check its capability to withstand the TRIEX-II operative conditions. In parallel, the compatibility with a lithium-lead environment was analyzed by exposing samples of niobium and 10CrMo9-10 (A335 P22) to a flow of the eutectic alloy at 500 °C up to 4000 h. Finally, the PAV mock-up was installed in the TRIEX-II facility. Full article

The oxidation-absorption technology of tail gas is perfect for natural gas purification plants to ensure the up-to-standard discharge of sulfur dioxide emissions, but it can produce a large amount of wastewater. In this paper, a facile and full-scale reuse treatment strategy based on the sequential combination of disc tube reverse osmosis and low-temperature and low-pressure evaporation desalination was proposed and studied. The produced light yellow wastewater was acid sulfate-rich organic wastewater, in which sulfate ions (SO₄²⁻) existed up to 6479 mg/L, and the chemical oxygen demand (COD), 5-day biochemical oxygen demand (BOD₅), total organic carbon (TOC), ammonia nitrogen (ammonia-N), total nitrogen (TN) and suspended solid (SS) were 207, 71.9, 67.6, 1.28, 70.5 and 20.9 mg/L, respectively. After the reuse treatment, there was COD (6 mg/L), BOD₅ (1.4 mg/L), TOC (0.9 mg/L), TN (2.07 mg/L), SS (6 mg/L) and SO₄²⁻ (90 mg/L) in permeated water, and condensate water with COD (11 mg/L), BOD₅ (2.3 mg/L), TOC (4.3 mg/L), SS (2 mg/L) and SO₄²⁻ (1.2 mg/L) was obtained. Thereby, pollution indexes were reduced after the reuse treatment so as to meet the water quality standard (GB/T18920-2022) in China, and the total water recovery rate reached 98.2 vol%. Ultimately, the priority pollutant migration mechanism during the reuse treatment process was determined. Full article

The interest of the fusion community in Pd–Ag membranes has grown in the last decades due to the high value of hydrogen permeability and the possibility of continuous operation, making it a promising technology when a gaseous stream of hydrogen isotopes must be recovered and separated from other impurities. This is the case of the Tritium Conditioning System (TCS) of the European fusion power plant demonstrator, called DEMO. This paper presents an experimental and numerical activity aimed at (i) assessing the Pd–Ag permeator performance under TCS-relevant conditions, (ii) validating a numerical tool for scale-up purposes, and (iii) carrying out a preliminary design of a TCS based on Pd–Ag membranes. Experiments were performed by feeding the membrane with a He–H₂ gas mixture in a specific feed flow rate ranging from 85.4 to 427.2 mol h⁻¹ m⁻². A satisfactory agreement between experiments and simulations was obtained over a wide range of compositions, showing a root mean squared relative error of 2.3%. The experiments also recognized the Pd–Ag permeator as a promising technology for the DEMO TCS under the identified conditions. The scale-up procedure ended with a preliminary sizing of the system, relying on multi-tube permeators with an overall number ranging between 150 and 80 membranes in lengths of 500 and 1000 mm each. Full article

Tritium extraction is one of the key open issues toward the development of the WCLL BB (Water-Cooled Lithium–Lead Breeding Blanket) of EU DEMO reactors, and different technologies have been proposed to address it. Among them, the Permeator Against Vacuum (PAV) has promising features, but it has never been tested in a relevant environment. This work presents the first experimental results ever obtained for a PAV mock-up. The experiments were carried out at ENEA Brasimone R.C. with the TRIEX-II facility on a mock-up characterized by a shell and tube configuration and using niobium as a membrane material. The experimental campaign was carried out with LiPb flowing at about 450 °C and 1.2 kg/s, while the hydrogen partial pressure was varied in the range 170–360 Pa. The characterization of the PAV performance was conducted by measuring the hydrogen partial pressure drop across the mock-up and the hydrogen permeated flux through a leak detector calibrated with an external hydrogen calibration cylinder. Moreover, the permeated flux was confirmed by a pressurization test performed measuring the pressure increase on the vacuum side of the PAV. The results constitute the first verification of the possibility to operate a PAV in flowing LiPb and to quantify its capabilities. Full article

Chabazite (CHA)-type zeolite membranes are a potential material for CO₂ separations because of their small pore aperture, large pore volume, and low aluminum content. In this study, the permeation and separation properties were evaluated using a molecular simulation technique with a focus on improving the CO₂ separation performance. The adsorption isotherms of CO₂ and CH₄ on CHA-type zeolite with Si/Al = 18.2 were predicted by grand canonical Monte Carlo, and the diffusivities in zeolite micropores were simulated by molecular dynamics. The CO₂ separation performance of the CHA-type zeolite membrane was estimated by a Maxwell–Stefan equation, accounting for mass transfer through the support tube. The results indicated that the permeances of CO₂ and CH₄ were influenced mainly by the porosity of the support, with the CO₂ permeance reduced due to preferential adsorption with increasing pressure drop. In contrast, it was important for estimation of the CH₄ permeance to predict the amounts of adsorbed CH₄. Using molecular simulation and the Maxwell–Stefan equation is shown to be a useful technique for estimating the permeation properties of zeolite membranes, although some problems such as predicting accurate adsorption terms remain. Full article

The aim of the current study was to enhance the oral bioavailability of Acyclovir (ACV) based on the papain-functionalized self-emulsifying drug delivery systems (SEDDS). The optimum control SEDDS formulation comprised of kolliphore (40%), transcutol (30%), propylene glycol (20%) and oleoyl chloride (10%). However, in the targeted SEDDS formulation, oleoyl chloride was replaced with oleoyl chloride-papain (OC-PAP) conjugate that was synthesized via an amide bond formation between the acyl halide groups of oleoyl chloride and the amino group of papain. Prior to adding in the SEDDS formulation, the newly synthesized conjugate was evaluated quantitatively by a Bradford assay that demonstrated 45 µg of papain contents per mg of the conjugate. Moreover, the conjugate formation was qualitatively confirmed through FTIR analysis and thin layer chromatography. ACV (a BCS class III drug) was incorporated into the SEDDS formulations after being hydrophobically ion paired with sodium deoxycholate, thereby making it lipophilic. The drug-loaded formulations were emulsified in the 0.1 M phosphate buffer (pH 6.8) and evaluated in vitro with respect to drug release and rabbit mucosal permeation studies. Both the formulations illustrated a very comparable drug release over a period of 4 h, afterwards, the OC-PAP-based formulation demonstrated a more sustaining effect. The extent of mucus diffusion evaluated via the silicon tube method demonstrated a 4.92-fold and a 1.46-fold higher penetration of the drug, a 3.21-fold and a 1.56-fold higher permeation through the rabbit intestinal mucus layer, and a 22.94-fold and a 2.27-fold higher retention of the drug over the intact mucosa of rabbit intestine, illustrated by OC-PAP-based nanoemulsions compared to the drug-free solution and controlled nanoemulsion, respectively. According to these in vitro results, papain-functionalized SEDDS is a promising approach for the oral delivery of ACV and many other drugs with oral bioavailability issues, however, in vivo studies in this respect have to be employed before making a comprehensive conclusion. Full article