Natural Porous Materials Research Articles

Valorization of Food Waste: Utilizing Natural Porous Materials Derived from Pomelo-Peel Biomass to Develop Triboelectric Nanogenerators for Energy Harvesting and Self-Powered Sensing.

Food waste is an enormous challenge, with implications for the environment, society, and economy. Every year around the world, 1.3 billion tons of food are wasted or lost, and food waste-associated costs are around $2.6 trillion. Waste upcycling has been shown to mitigate these negative impacts. This study's optimized pomelo-peel biomass-derived porous material-based triboelectric nanogenerator (PP-TENG) had an open circuit voltage of 58 V and a peak power density of 254.8 mW/m2. As porous structures enable such triboelectric devices to respond sensitively to external mechanical stimuli, we tested our optimized PP-TENG's ability to serve as a self-powered sensor of biomechanical motions. As well as successfully harvesting sufficient mechanical energy to power light-emitting diodes and portable electronics, our PP-TENGs successfully monitored joint motions, neck movements, and gait patterns, suggesting their strong potential for use in healthcare monitoring and physical rehabilitation, among other applications. As such, the present work opens up various new possibilities for transforming a prolific type of food waste into value-added products and thus could enhance long-term sustainability while reducing such waste.

Experiments reveal effects of particle and pore-scale heterogeneity on thermal dispersion during porous media heat transport

The growing applications of heat transport in engineering and hydrogeology, including ground source heat pump systems and the assessment of water flow and sediment thermal properties, necessitate precise thermal dispersion modeling. Despite various factors like particle size, shape, and distribution impacting dispersion in porous media, a lack of experimental data and analysis has limited our grasp of the relationship between flow velocity and thermal dispersion. To address this gap, we conducted solute and heat tracer experiments using sands of different grain sizes, employing analytical models based on a universal power law relationship for dispersion. Additionally, we systematically compiled dispersion data from the scientific literature to assist in interpreting of the effects of particle size, shape, and pore-scale heterogeneity on dispersion. Our findings reveal that solute and thermal longitudinal dispersion align for high flow velocities in the dispersion-dominated flow regime (Pe > 5), where the velocity-dispersion relationship is linear. However, in the transition regime (advection approx. equal to diffusion, 0.1–0.3 < Pe < 5), the observed deviation from linearity (R2<0.9) is linked to increased pore-scale heterogeneity, particularly in smaller particle sizes. This study underscores the pivotal role of thermal dispersion and underscores the need for caution when estimating thermal dispersion based on solute dispersion, given the intricate nature of real-world conditions and the potential influence of factors such as grain size distribution and pore-scale heterogeneity in natural porous materials.

Nitrogen and Sulfur Co-doped Biomass-Derived Porous Carbon Electrodes for Ultra-High-Performance All-Aqueous Thermally Regenerative Flow Batteries.

Developing high-performance electrodes for the all-aqueous thermally regenerative ammonia battery (ATRB) system, serving as superior substitutes for commercial carbon cloth electrodes, is anticipated to enhance performance, yet it lacks effective guidance and research. In this work, theoretical analysis is initially used to evaluate the effective conversion and adsorption capacity of nitrogen and sulfur co-doped carbon with respect to copper ion by density functional theory calculation. On the basis of this concept, the nitrogen and sulfur co-doped biomass-derived porous carbon electrode (DGC) is prepared using natural porous carbon materials and thiourea. Compared with commercial carbon cloth electrodes, ATRB with DGC achieves a significant improvement in maximum power density of 49.2%. Via optimization of the doping conditions, the active sites can be effectively regulated to boost charge transfer at the reaction interface. Furthermore, the rapid charge transfer can match the excellent mass transfer performance, generating an impressive net power density of 847.5 W/m2.

Effects of Particle Size Reduction on the Pore Structure and Accessibility in Natural Porous Materials

Effects of Particle Size Reduction on the Pore Structure and Accessibility in Natural Porous Materials

Acoustic and thermal properties of panels made of fruit stones waste with coconut fibre

Using natural porous and fibrous materials for acoustic and thermal conditioning in the construction sector is a solution to achieve a comfort level in buildings. The novelty of this research work lies in employing agricultural and agro-industry waste to solve noise and thermal insulation problems. This study was conducted to investigate a multilayered panel made of fruit stones and coconut fibre from agro-industry waste. Acoustic absorption, and acoustic and thermal transmission, tests were run on four different fruit stone types, olive, cherry, apricot and peach, plus a coconut fibre layer. Although they are not structural elements, bending tests were run to ensure panels’ structural integrity. Acoustic tests complied with the recommendations of Standards ISO 10534–2 and ASTM E 2611–09, based on the standing wave tube to obtain the acoustic absorption coefficient and sound transmission loss, respectively. Standard EN 12667 was considered for the thermal test to determine the thermal conductivity coefficient based on the hot plate method. The results show an average sound absorption coefficient above 0.5 and sound insulation over 25 dB within certain frequency ranges. The cherry panels had absorption values of around 0.7 and apricots had sound insulation values of up to 30 dB. Samples’ thermal transmittance coefficient values were between 3.0 and 3.4 (W/m2K), which indicate panels’ ability to provide thermal insulation. The cherry and olive panels obtained the lowest thermal conductivity (around 0.14 W/mK). The backing effect of the coconut fibre layer improves all the panels’ acoustic absorption and thermal properties.

AI-Enabled Materials Design of Non-Periodic 3D Architectures With Predictable Direction-Dependent Elastic Properties.

Natural porous materials have exceptional properties-for example, light weight, mechanical resilience, and multi-functionality. Efforts to imitate their properties in engineered structures have limited success. This, in part, is caused by the complexity of multi-phase materials composites and by the lack of quantified understandingof each component's role in overall hierarchy. This challenge is twofold: 1) computational. because non-periodicity and defects render constructing design guidelines between geometries and mechanical properties complex and expensive and 2) experimental. because the fabrication and characterization of complex, often hierarchical and non-periodic 3D architectures is non-trivial.

Physicochemical characteristics of natural and anthropogenic inorganic and organic solid porous materials: Comprehensive view

Complex textural analyses and ultimate analyses of 23 inorganic and organic solid porous materials of natural and anthropogenic origin have been performed. The type of pores, porosity and pore size distributions are discussed. While Halloysite, Biocalith K and Diatomaceous earth have a balanced distribution of all pores, Clinoptilolite and Kemira have a high micropore content and Montmorillonite contain predominantly mesopores. SH-GC has the highest micro-mesopore content. Natural materials and materials prepared from raw materials have SBET values <50 m2/g, whereas materials on the basis of activated carbon and montmorillonite or pure granulated Fe(OH)3 have SBET > 50 m2/g. The highest porosity values correspond with an extremely high content of macropores in the Eco-Dry Compact and Eco-Dry Plus samples, and in the Wood sawdust samples, where at the same time the presence of the smallest pores is sporadic. The highest micropore values were observed in a sample from the category of aluminosilicates and in samples of activated carbon. Overall, the diverse variability of the properties of these solid porous unconventional materials was revealed, which offers the possibility of wide use for various types of adsorption, both in raw form and after appropriate material treatment. The material is discussed for the suitability of using to remove specific types of pollutants.

Thermal conductivity analysis of natural fiber-derived porous thermal insulation materials

Natural fibers, derived from plants such as wood, hemp, straw and cotton, have been explored for the fabrication of porous structures for thermal insulation applications due to their widespread availability, sustainability, and cost-effectiveness. Understanding the fundamental heat transfer mechanisms within natural fiber-derived porous structures is crucial for both optimized geometric design and real-world insulation applications. Herein, we developed a theoretical framework considering geometric parameters, including pore size, fiber diameter and porosity (i.e., density), to examine the contribution of various heat transfer modes (i.e., conduction, convection, and radiation) on the effective thermal conductivity of porous structures derived from natural fibers. Our results indicate that thermal radiation is largely responsible for the rapid increase in effective thermal conductivity of the natural fiber-derived porous insulations in low-density regions (< 50 kg/m3) and that natural convection rarely occurs within these materials. The insulation materials derived from natural fibers with diameters in the micron range (5–50 μm) can achieve their minimum thermal conductivity at an optimal density of 50–90 kg/m³. Effective strategies to lower the effective thermal conductivity of natural fiber-derived porous materials include increasing porosity to curtail solid conduction, incorporating nanoscale pores by using nanosize fibers to diminish gaseous thermal conductivity. This research offers valuable insights into the heat transfer mechanisms in natural fiber-derived materials and should guide the structural design and optimization process toward developing super-thermal insulation materials derived from natural fibers.

Modified balsa wood with natural, flexible porous structure for gas storage

The utilization and transportation of clean energy require efficient energy storage solutions. Gas hydrate represents a promising way for high-density storage under mild conditions. In particular, hydrate induced by confined space has the advantage of being environmentally friendly with rapid nucleation and high mass transfer efficiency. However, the cost of artificial pore-construction methods has hindered its widespread application. In this study, we report a novel approach of hydrate storage in the -SO3− modified flexible balsa wood as a naturally porous material. The surface sulfonate groups were successfully grafted by coupling agents which was verified by various techniques. The material's natural porous hierarchical structure allows for efficient fluid flow in porous media, enabling a reduction in induction time by ∼88% and a storage capacity of up to 150.6 v/v by adjusting the load water amount. The 100 wt% water-loaded wood materials exhibited the highest water conversion efficiency. Moreover, the recoverable mechanical properties make it reusable without performance degradation. The inner pore structure and hydrate morphologies were further investigated by X-ray microscopy to clarify the hydrate growth mechanism. The interconnected pores and channels make the hydrate grow in layers inside. In addition, the performance could be adjusted by simply changing the hydrophobicity to regulate the gas flow which may contribute to the large storage systems. The use of natural biomass porous materials provides an environmentally friendly and economically feasible strategy for gas storage.

Structure and mechanisms of foam-like bamboo parenchyma tissue

The increased awareness of environmental problems has shifted the attention from synthetic polymer porous materials to natural plant porous materials like bamboo parenchyma tissue to develop functional materials. However, the neglect of the inherent structure and property of plant porous materials leads to insufficient development and utilization of their natural advantages. Here, we investigated the fine structure and mechanisms of bamboo parenchyma tissue, which has multiple high-quality properties like energy-absorbing and toughening, to provide a basis for their wide utilization in porous materials. Results showed that bamboo parenchyma tissue was a foam-like porous material with sufficient strength, high porosity and low density. It was composed of cell walls and four types of three-dimensional polyhedral pores converging in space. The total natural porosity was up to 78.80%. The cell walls exhibited a three-zone strength distribution with an average solid cell wall strength of 75.84 MPa, due to their cocoon-like closed microfibrils patterns, chemical compositions and pits characteristics. The high porosity and weakening of transition zone and cell end wall helped to absorb energy. This study provides ideas for the application of bamboo parenchyma tissue in cushioning energy-absorbing foam materials and porous material templates and for the biomimetic design of environmentally friendly porous materials.

Numerical analysis of the heat transfer and fluid flow of a novel water-based hybrid photovoltaic-thermal solar collector integrated with flax fibers as natural porous materials

Photovoltaic thermal (PVT) collector-based active cooling technology makes it possible to increase the efficiency of PV solar cells and meanwhile generate heat through the direct conversion of solar irradiation into electricity. Hence, this study presents a detailed numerical analysis of the thermal performance of PVT solar collectors integrated with flax fibers as natural porous materials. To achieve this goal, a cooling channel is proposed, which contains porous flax fiber materials doping in pure water as a cooling fluid for the photovoltaic panels. A particular focus of this research is emphasized on the effects of the thickness of the porous material layer (5−50 mm), the solar flux (50−1000 W/m2), and the flow rate of coolant (0.40−1.0 m/s), to determine the best thickness of the porous material and the cooling fluid flowrate that achieves the highest performance of photovoltaic panels. The simulations are performed using ANSYS software, Navier Stokes equations, and Darcy-Brinkman-Forchheimer porous model. Moreover, the thermal performance of the proposed PVT system cooled with water/porous flax fibers mixture is analyzed and compared with the PVT collector using pure water and air as a coolant. The results presented that the optimal design for maximization of the cooling of photovoltaic panels is attained by incorporating porous flax fibers materials with a thickness of 50 mm and 0.907 m/s cooling water flowrate. It is indicated that the Nusselt number is increased from 18.65 to 51.0, with an improvement of 173.46% as compared to the use of only pure water at the optimal conditions. Moreover, the thermal efficiencies of the PVT system are obtained as 69.58%, 50.02%, and 34.60% using water with a flax fibers layer, pure water, and air, respectively.

Novel modified triply periodic minimal surfaces (MTPMS) developed using genetic algorithm

The desirable properties of natural porous materials have inspired humans to design cellular materials with remarkable properties such as high energy absorption, acoustic and thermal insulation, and high specific strength structures. Triply Periodic Minimal Surface (TPMS) structures are particularly important among the architected materials. In this research, we have developed a novel approach based on a genetic algorithm for geometry modification of TPMS structures. The approach is exploited to enhance the effective thermal and mechanical properties of TPMS structures, namely Primitive, IWP, Gyroid, and GPrime. New modified TMPS structures (MTPMS) have much higher Young's modulus and thermal conductivity than their base structures, and some of them have properties very close to the upper Hashin-Shtrikman bounds. Unlike previous studies conducted to improve the properties of TPMS structures, MTPMS can be expressed by simple equations. Although MTPMS are not generally considered minimal surfaces, they nonetheless possess the desirable geometric qualities of TPMS structures, such as being smooth and splitting space into two non-intersecting and continuous domains, etc.

Advanced NMR Cryoporometry

AbstractAccurate structural characterization of mesoporous solids is of importance for potential applications and for better understanding of properties of natural porous materials. Among different characterization techniques, thermoporometry has several beneficial features, such as applicability to wetted and soft materials. In this review, we discuss recent advancements concerning nuclear magnetic resonance cryoporometry allowing for a notable improvement of the accuracy of this method.

A Recombinant Parathyroid Hormone-Related Peptide Locally Applied in Osteoporotic Bone Defect.

The local application of drug-loaded bioactive scaffold materials is one of the important directions to solve the clinical problem of osteoporotic (OP) bone defects. This study retains the advantages of drug loading and mechanical properties of natural 3D bioactive scaffolds. The scaffolds are functionally modified through chemical and self-assembly approaches with application of polydopamine (PDA) nanoparticles and parathyroid hormone-related peptide-1 (PTHrP-1) for efficient local drug loading. This study investigates the effects of the novel bioactive scaffolds on ossification, osteoclastogenesis, and macrophage polarization. This work elucidates the effects of the scaffolds in regulating osteoclastic activity and new bone formation in vitro. Further studies on the establishment and repair of OP bone defects in small animals are conducted, and the potential of natural bioactive porous scaffold materials to promote the repair of OP bone defects is initially verified. The preparation of safe and economical anti-OP bone repair material provides a theoretical basis for clinical translational applications.

Confined phase behavior of ethane in nanoporous media: An experimental investigation probing the effects of pore size and temperature

Ethane is rapidly becoming an efficient and dependable clean energy source for fast-growing and developing countries. It is the second most abundant natural gas after methane. However, it poses a major problem for ozone pollution and plays a significant role in greenhouse warming once released into the atmosphere. Therefore, understanding the mechanisms that govern its behavior during storage in natural and artificial nanoporous materials is essential for numerous industrial and environmental applications. In this work, the confined phase behavior of ethane was investigated in ordered mesoporous silica material MCM-41 at varying nanoscale-pore sizes and temperatures. Adsorption and desorption isotherms were experimentally measured for a wide range of nanopore diameters (7, 10.2, 11.3, and 12.3 nm) and temperatures (varying from −65 to −20 °C) using an automated gravimetric nanocondensation apparatus. This system enabled direct quantification of the mass of ethane adsorbed onto the surfaces of nanopores. We examined the impact of the pore diameter and temperature on the adsorption, capillary condensation, and evaporation of ethane in nanoporous media. The capillary condensation and evaporation pressures were determined using the Lorentzian functions. The accuracy of the measurements was confirmed by comparing the experimental bulk condensation pressures with those reported by the National Institute of Standards and Technology (NIST).The results demonstrate that the capillary condensation pressures increased with ascending pore diameters and temperatures. They also indicate that the degree of suppression of the saturation pressure due to confinement is predominant at low temperatures. The percent reduction in the pressure of vapor-liquid phase change decreased with an increase in temperature. A similar trend was observed with respect to changes in the pore size. The results showed that the effect of confinement was weakened as the nanopores became wider. Furthermore, insights were developed about the effects of pore diameter and temperature on the occurrence of the supercritical-like behavior of ethane in nanopores. A good agreement was evident between our results and the examples available in the literature.To the best of our knowledge, we present the first experimental study that describes the confined phase behavior of ethane using a patented gravimetric apparatus. This work presents a systematic approach to understand the effects of confinement in nanoporous media. Furthermore, it can aid the development of new ethane storage applications, especially the characterization of natural and artificial porous materials for energy and environment-related solutions.

Additively Manufactured Lattice Materials with a Double Level of Gradation: A Comparison of Their Compressive Properties when Fabricated with Material Extrusion and Vat Photopolymerization Processes.

Natural porous materials adjust their resulting mechanical properties by the optimal use of matter and space. When these are produced synthetically, they are known as mechanical metamaterials. This paper adds degrees of tailoring of mechanical properties by producing double levels of gradation in lattice structures via cross-section variation in struts in uniformly periodic lattice structures (UPLS) and layered lattice structures (LLS). These were then additively manufactured via material extrusion (ME) and vat photopolymerization (VP). Their effective mechanical properties under compressive loads were characterized, and their stiffness contrasted with finite element models (FEM). According to the simulation and experimental results, a better correlation was obtained in the structures manufactured via VP than by ME, denoting that printing defects affect the correlation results. The brittle natural behavior of the resin caused a lack of a plateau region in the stress-strain curves for the UPLS structures, as opposed to those fabricated with ME. The LLS increased energy absorption up to 244% and increased the plateau stress up to 100% compared to the UPLS. The results presented in this paper demonstrate that the mechanical properties of lattice structures with the same base topology could be modified by incorporating variations in the strut diameter and then arranging these differently.

Eggplant biomass based porous carbon for fast and efficient dye adsorption from wastewater

Adsorption techniques have been successfully applied in water purification for their simplicity, efficiency, and negligible byproducts. Porous carbon materials are effective dye adsorbents but have relatively low adsorption efficiency, slow adsorption rate, and high production cost, all of which need to be addressed for conducive practical applications. Herein, natural eggplant-based porous carbon materials (EPCMs) have been studied and successfully constructed to perform with high efficiency and fast rate of removal of dyes from wastewater. The hierarchical pore structure and well-developed mesoporous had a total pore volume of 0.6379 cm 3 /g and a maximum specific surface area of 516.0060 m 2 /g, which contributed to the high efficiency of adsorption (100%). The complete adsorption of Rhodamine B (basic and cationic dyes) solution within 25 min demonstrated its fast and high adsorption performance. The EPCMs also showed its efficiency in the absorption of various dyes, including methyl orange (acidic and anionic dye), methylene blue (basic and cationic dyes), and Yuan’qing B (reactive dye). Furthermore, the EPCMs were tested with actual wastewater from a production-based factory and recorded excellent removal effects as well, suggesting its prospective expansion for industrial applications. Therefore, this eggplant biomass-based porous carbon provides a promising approach for fast and highly efficient wastewater purification from dye-based contaminations. • Eggplant biomass carbon is developed for dye adsorption from wastewater. • The EPCMs show fast and high-efficient dye adsorption capacity. • The EPCMs can remove various types of dyes with high efficiency. • The EPCMs exhibit excellent removal effects for the actual dyeing wastewater.

Anisotropic cellulose nanofibril aerogels fabricated by directional stabilization and ambient drying for efficient solar evaporation

Anisotropic aerogels, mimicking natural porous materials such as wood and bone, always exhibit distinctive properties due to their aligned channels, which, however, generally require complicated ice templating configuration and costly freeze-drying. In this work, we develop a novel, facile, low-cost, and scalable method combining directional stabilization and ambient drying to prepare anisotropic aerogels. The frozen aqueous TEMPO-oxidized cellulose nanofibrils (TOCNFs) monolith embedded in a mold is directly immersed in ethanol/Fe3+ bath. The ice crystals directionally dissolve in ethanol, and simultaneously the TOCNFs are directionally stabilized due to the electrostatic complexation between their carboxyl groups and Fe3+ ions. The obtained anisotropic nanocellulose aerogel (NCA) after ambient drying exhibits an ordered porous structure, which is tunable by adjusting the contents of carboxyl groups on TOCNFs. The NCAs reveal distinct anisotropy, excellent mechanical compressibility in the radial direction, and high water-stability. To demonstrate their promising potentials for application in various advanced fields such as solar steam generation, the NCA is coated with polypyrrole (PPy) by in-situ polymerization to achieve excellent photothermal property but well maintain the original aligned channels of NCA, which endow the NCA@PPy with an efficient solar evaporation performance.

Enhancing the productivity of hemispherical solar distillers using dyed flax fibers as natural inexpensive porous materials

The rise in the global population over the past years has made freshwater supplies essential for all vital operations. Desalination is now essential for ensuring the sustainability of the world's population. To boost the output of solar distillers, the present experimental study aims to utilize natural inexpensive porous materials to improve the evaporation rates within the distillers, and hence boost their productivity. To achieve this idea, the flax fibers were added to a basin of hemispherical distillers as natural porous materials. To find out how dyed flax fibers affect the productivity of hemispherical distillers, we designed and constructed three simple hemispherical distillers, and compared their performance under the same climate conditions. While the first simple hemispherical distiller (SHD) represented the reference distiller, the second and third simple hemispherical distillers were enhanced with natural yellow flax fibers (SHD-YF) and black dyed flax fibers (SHD-BF), respectively. The results showed that, by employing the natural yellow flax fibers (SHD-YF) and black dyed flax fibers (SHD-BF), the cumulative yield increased by 29.7 and 39.6%, respectively, compared to the reference distiller. Additionally, it was found that the hemispherical distiller utilizing black-dyed flax fibers (SHD-BF) produced distillate water 7.63% more than the hemispherical distiller that used the same material without dyeing (SHD-YF). The SHD-BF has a maximum daily thermal efficiency of 57.31%, which is 39.34% higher than the SHD maximum efficiency. The thermo-economical feasibility showed that using black dyed flax fibers as natural porous materials is a viable option to improve the productivity of solar distillers.

3D Natural Mesoporous Biosilica-Embedded Polysulfone Made Ultrafiltration Membranes for Application in Separation Technology.

Diatoms are the most abundant photosynthetic microalgae found in all aquatic habitats. In the extant study, the spent biomass (after lipid extraction) of the centric marine diatom Thalassiosira lundiana CSIRCSMCRI 001 was subjected to acid digestion for the extraction of micro composite inorganic biosilica. Then, the resulting three-dimensional mesoporous biosilica material (diatomite) was used as a filler in polysulfone (PSF) membrane preparation by phase inversion. The fabricated PSF/diatomite composite membranes were characterized by SEM-EDX, TGA, and ATR-IR, and their performances were evaluated. The number of pores and pore size were increased on the membrane surface with increased diatomite in the composite membranes as compared to the control. The diatomite composite membranes had high hydrophilicity and thermal stability, lower surface roughness, and excellent water permeability. Membranes with high % diatomite, i.e., PSF/Dia0.5, had a maximum water flux of 806.8 LMH (Liter/m2/h) at 20 psi operating pressure. High-diatomite content membranes also exhibited the highest rejection of BSA protein (98.5%) and rhodamine 6G (94.8%). Similarly, in biomedical rejection tests, the PSF/Dia0.5 membrane exhibited a maximum rejection of ampicillin (75.84%) and neomycin (85.88%) at 20 Psi pressure. In conclusion, the mesoporous inorganic biosilica material was extracted from spent biomass of diatom and successfully used in filtration techniques. The results of this study could enhance the application of natural biogenic porous silica materials in wastewater treatment for water recycling.