Search Results (70)

Hydrothermal carbonization (HTC) of digested dairy manure produces hydrochar and a nitrogen-rich post-liquid. This study evaluated a submerged tubular expanded polytetrafluoroethylene (ePTFE) gas-permeable membrane (GPM) system for ammonia recovery from post-HTC liquid derived from digested dairy manure, focusing on the effects of feed temperature, acid circulation rate, and feed volume-to-membrane surface area ratio (FV/MS). Compared with filtered digested manure, the post-HTC liquid had a similar total ammoniacal nitrogen (TAN) concentration (1151 vs. 1164 mg N L⁻¹) but a slightly higher pH (8.38 vs. 7.94), which favored ammonia transfer. Increasing feed temperature from 20 to 60 °C raised 24 h TAN recovery from 63.5% to 99.6% and average TAN transfer flux from 11.1 to 17.7 g m⁻² d⁻¹, although it also increased water vapor crossover and diluted the acid trapping solution. Increasing acid circulation from 10 to 30 mL min⁻¹ improved 48 h TAN recovery from 85.2% to 94.0%, while a further increase to 50 mL min⁻¹ produced only a small additional gain. In contrast, elevating FV/MS from 0.015 to 0.045 m³ m⁻² reduced 48 h TAN recovery from 94.0% to 59.6% while increasing average TAN transfer flux from 8.2 to 16.2 g m⁻² d⁻¹ because larger feed volumes sustained the concentration driving force for a longer period. Nitrogen mass balance showed that more than 94–99% of the initial TAN was accounted under most conditions, with only a small fraction lost to volatilization. Full article

High-solid anaerobic digestion (HS-AD) is one of the most efficient and popular solid-waste-treatment and energy-recovery technologies. However, it is significantly influenced by composition and substrate characteristics, with the carbon-to-nitrogen ratio (C/N ratio) and biodegradability being important. In this study, the substrate was adjusted and compounded to investigate the methanogenesis performance with the substrate C/N ratio (2.82–82.72) and biodegradability (refractory and easily degraded) variation during HS-AD. The results showed that the highest methane yield (MY) was achieved with white meat (273.02 mL/g-VS), which was 2.22 times higher than that of substrates with higher C/N ratios. However, this enhanced methane productivity was accompanied by elevated total ammonia nitrogen (TAN) concentrations, which substantially increased the risk of system instability. For a high C/N ratio (>50:1), the difference between the C/N ratio and biodegradability had little influence on MY, and under a low C/N ratio (<5:1), the methane production rate was higher. For low C/N substrates, acetic (14.53–76.82%) accounted for the highest total volatile fatty acids (VFAs) during HS-AD, and for high C/N ratio substrates, propionic (46.44–82.66%) had a higher proportion (r = 0.94). An increased C/N ratio decreased total ammonia nitrogen (TAN) and alkalinity (p < 0.05). Variations in the C/N ratio and biodegradability led to differences in the microbial composition. Full article

Glass-transition-driven shape memory polymers are promising materials for 4D printing because their thermally activated transition enables programmed deformation and recovery without relying on melting or crystallization-driven switching. In this study, PDMS-MMA-modified photocurable networks were designed for vat photopolymerization-based 4D printing by varying PDMS-MMA content and switching monomer structure while maintaining a fixed TMPTMA crosslinker content. The resin formulations were prepared using tert-butyl acrylate (tBA) or isobornyl acrylate (IBOA) as switching monomers, PDMS-MMA as a flexible mobility-regulating segment, and TMPTMA as a multifunctional crosslinker. The effects of formulation composition on printability, network formation, thermal stability, thermomechanical transition, mechanical properties, and shape memory behavior were systematically investigated. FT-IR analysis confirmed effective photocuring of the acrylate/methacrylate networks, while rheological evaluation showed that resin viscosity depended on monomer structure and PDMS-MMA content. DMA results revealed thermomechanical transition, although some formulations exhibited broad tan δ responses due to network heterogeneity and distributed segmental relaxation. Based on resin printability, printed-part resolution, and relatively well-defined tan δ transitions, T-15 and I-15 were selected as representative formulations for quantitative shape memory evaluation. Shape memory testing was conducted under force-control mode because stable strain-controlled programming was not achievable for the printed specimens. Both T-15 and I-15 exhibited high shape fixity over two programming–recovery cycles. I-15 showed stable recovery behavior with recovery ratios of 91.51% and 95.87%, whereas T-15 showed apparent over-recovery with recovery ratios exceeding 100%, likely due to residual stress release during reheating. Overall, these results demonstrate that thermally activated shape-memory performance is governed not only by the nominal transition temperature but also by the coupled effects of PDMS-mediated segmental mobility, switching monomer structure, mechanical integrity, and elastic energy storage within a fixed crosslinked network framework. Full article

The increasing demand for sustainable materials in additive manufacturing has driven the development of bioplastics derived from renewable biomass, including microalgae. In this study, the rheological behavior of a 20 wt.% aqueous gel prepared from native Chlorella vulgaris (C. vulgaris) starch, plasticized with 30 wt.% glycerol, was investigated to assess its suitability for extrusion-based 3D printing (direct-ink-writing, DIW). Steady shear analysis revealed a pronounced yield stress (${\tau }_0$ = 271.93 Pa) and strong shear-thinning behavior, described by the Herschel–Bulkley model (K = 59.47 Pa·sⁿ, n = 0.67), indicating structural stability at rest and efficient flow under shear. Oscillatory measurements confirmed a predominantly elastic response, with storage modulus (G′ $\approx$ 13,500 Pa) greatly exceeding loss modulus (G″) and a low loss factor (tan $\delta \approx$ 0.1), demonstrating gel integrity and shape retention. Temperature-dependent analysis indicated enhanced network strength without thermal softening, while thixotropic recovery tests showed rapid structural rebuilding after shear removal. Notably, a $~$50% increase in G′ during recovery highlights improved interlayer adhesion potential. These results show that C. vulgaris starch exhibits the key rheological characteristics required for DIW-type extrusion printing, including yield stress, shear-thinning behavior, viscoelastic stability, and rapid recovery, making it a promising candidate for this application. Full article

Processing parameters play a key role in the mechanical, thermo-mechanical and creep-recovery properties of unidirectional carbon fiber reinforced thermoplastic polypropylene (CF/PP) composites because of high matrix viscosity, which governs their impregnation and interfacial bonding. This study systematically investigates the effects of molding temperature (190~210 °C), pressure (1~3 MPa), and holding time (5~15 min) on its short beam strength (SBS), storage modulus, loss modulus, tan δ, creep strain, strain recovery, and crystallinity using a Taguchi experimental design. The results presented that processing parameters have a huge effect on CF/PP composites’ SBS, and through the experimental design, the SBS could be improved by 68.1% (21.3~35.8 MPa). Holding time is the most influential parameter for SBS and damping performance, while temperature and pressure interact strongly, highlighting the importance of parameter synergy. There was a strong negative correlation between the crystallinity degree and the SBS of CF/PP composites, and a higher crystallinity degree means a sharper and higher melting peak. Creep-recovery tests reveal near-complete recovery (87~102%) at 30 °C, which decreases to 71~79% at 80 °C due to increased matrix mobility. Finally, it was confirmed that the relatively low SBS of CF/PP composites comes from the void and incomplete matrix impregnation of fibers. The above results advance the design of high-performance, sustainable thermoplastic composites for civil and structural engineering applications. Full article

The temporal dynamics of nitrogen (N) fractions and ammonia (NH₃) volatilization were investigated over a 56-day storage period using a laboratory-scale pig slurry pit simulator. A detailed N mass balance, encompassing total N (TN), total ammonium N (TAN), organic N, and nitrate N (NO₃⁻-N) fractions, yielded a N mass recovery of 96.5%, despite uncertainties associated with discrete emission measurements, with a TN reduction of 28.3 g vessel⁻¹ closely matched by cumulative NH₃-N emissions of 27.3 g. The NH₃ emission profile exhibited a distinct two-phase pattern. During Phase I (days 1–28), emissions remained stable at 16.7–19.5 g m⁻² d⁻¹, accounting for approximately 58% of total cumulative NH₃-N loss (518.6 g m⁻²), consistent with zero-order kinetics. Phase II (days 29–56) was characterized by first-order exponential decay (k = 0.0293 d⁻¹, R² = 0.982), coinciding with progressive TAN depletion. Measured emission rates were strongly correlated with theoretical free ammonia N (FAN) concentrations derived from pH and temperature (R² = 0.74), confirming that theoretical FAN provides a useful upper bound for emission potential, although the actual gaseous flux is restricted by mass-transfer limitations at the slurry–air interface. These results demonstrate that continuous pH and temperature monitoring provides a practical basis for tracking emission dynamics and informing the timing of mitigation interventions, particularly during the high-flux initial storage phase. Full article

Proso millet (Panicum miliaceum L.) is being increasingly used in gluten-free baking; however, the influence of cultivar-dependent functionality on gluten-free dough remains insufficiently characterized. This study systematically evaluated the impact of nine proso millet cultivars (Cope, Dawn, Sunrise, Earlybird, Huntsman, Minco, Panhandle, Plateau, and Rise) on dough rheology, bread quality, and texture stability in a gluten-free formulation. Dough viscoelasticity was characterized using small-amplitude oscillatory shear (G′, G″, tan δ) and creep–recovery (J_end, J_nr, J_r/J, strain recovery, and t₉₀). Breads were then evaluated for specific volume, crust and crumb color, and texture profile analysis (TPA) over 0, 2, and 5 days of storage. All doughs exhibited weak gel behavior (tan δ = 0.30–0.36) with G′ consistently exceeding G″. The waxy, low-amylose cultivar Plateau produced the stiffest dough (highest G′ and G″) and the lowest loaf specific volume (1.97 mL/g), whereas Rise and Earlybird yielded the greatest expansion (2.43–2.40 mL/g). Storage induced typical staling (increased firmness, decreased springiness, cohesiveness, and resilience) with cultivar-dependent retention of elastic attributes linked to rheological parameters. Overall, cultivar starch structure impacts dough viscoelasticity, loaf expansion, and texture evolution, highlighting cultivar selection as a practical route to improve gluten-free bread quality and shelf-life consistency. Full article

Ground deformation monitoring is pivotal for enhancing urban resilience and mitigating geohazards. This study presents a synergistic monitoring framework integrating 26 Sentinel-1A (C-band) and 16 LuTan-1 (L-band) SAR scenes acquired between December 2023 and August 2025 to characterize the deformation dynamics in Beijing. Utilizing SBAS-InSAR, we first established a regional deformation baseline using Sentinel-1A observations, identifying critical subsidence and uplift zones in the eastern plains. Subsequently, high-resolution (3 m) LT-1 data were leveraged to achieve refined spatiotemporal characterization of these deformation hotspots. Validation against ground leveling benchmarks confirmed that both satellites yield high accuracy. LuTan-1 (RMSE = 3.810 mm/a) shows slightly better agreement with the ground leveling data than Sentinel-1A (RMSE = 4.853 mm/a). Analysis of the spatiotemporal patterns derived from InSAR revealed that the study area is characterized by widespread gene uplift (averaging ~10 mm/a), interspersed with acute localized subsidence exceeding 40 mm/a. Correlation analysis demonstrates a high spatiotemporal coupling between the extent and rate of surface uplift and groundwater level recovery. To further investigate these dynamics, Terzaghi’s effective stress principle is employed to quantify the contribution of groundwater level fluctuations to the observed surface deformation. A Parametric Harmonic Model was implemented to decouple elastic and trend components, and attribution analysis confirms that the continuous recovery of groundwater levels is the fundamental driver of the regional surface uplift. The inverted elastic skeletal storativity (S_ke), ranging from 1.587 × 10⁻³ to 9.184 × 10⁻³, reveals that regional surface uplift is predominantly driven by the elastic rebound of aquifer systems following groundwater recovery. In contrast, localized subsidence anomalies observed at large-scale engineering construction sites, landfill facilities, major expressway corridors, and high-density residential areas are independent of groundwater fluctuations, instead they are primarily attributed to anthropogenic stressors. This study elucidates a dual-drive mechanism, which comprising macroscopic hydrogeological rebound and localized anthropogenic disturbance, providing a robust scientific basis for differentiated urban hazard management. Full article

Thermal microbial mats are laminated organo-mineral biofilms composed of extracellular polymeric substances (EPSs) and microbially mediated silica and carbonate phases. Although extensively studied from ecological and geobiological perspectives, their potential as precursors for applied, bio-derived composite materials remains largely unexplored. In this study, geothermal microbial mats from the Comanjilla hot springs (Mexico) are investigated from a materials-oriented perspective through controlled processing, inorganic tanning, and polymeric surface conditioning. The mats were treated with potassium alum and reinforced using a polyvinyl alcohol–alginate–glycerin formulation to improve cohesion, handling behavior, and structural stability. Mineralogical, physicochemical, and microstructural analyses reveal a hierarchical laminated architecture in which EPS functions as a continuous organic matrix, while in situ silica and carbonate phases provide intrinsic mineral reinforcement. Carbonate-rich mats yield softer and more flexible composite materials, exhibiting tensile strength values of 2.17 ± 0.18 MPa and elongation at break of 15–20%, whereas silica-rich mats produce stiffer and more abrasion-resistant systems. Thermal analysis shows a main organic decomposition event near 275 °C and a stable inorganic residue of approximately 45–50 wt%, confirming the hybrid organo-mineral nature of the processed materials. Prototype-scale fabrication demonstrates structural cohesion, controlled porosity, elastic recovery, and breathability, supporting potential low-load and non-structural applications. Overall, the results identify geothermal microbial mats as a renewable and naturally pre-assembled platform for bio-derived organo-mineral composite materials and provide a foundation for future studies focused on controlled processing and structure–property optimization. Full article

Tuna-processing facilities produce substantial amounts of concentrated organic residues and sludges containing high levels of proteins, lipids, and nitrogen, which are not easily handled by conventional waste treatment methods. In this work, the anaerobic digestion (AD) performance of tuna-processing by-products (TPB1–2) and associated wastewater sludges (TWS1–3) was investigated using a combination of biochemical methane potential (BMP) tests, theoretical methane yield calculations based on the Buswell–Boyle equation, semi-continuous mono-digestion experiments, and 16S rRNA gene-based microbial analyses. Among the evaluated materials, TWS2 produced the highest methane yield (554.6 N mL CH₄/g VS) and, when its annual production volume was taken into account, showed the greatest estimated energy recovery (approximately 1.88 × 10⁶ kWh per year). By contrast, TWS3 exhibited the lowest methane yield (239.8 N mL CH₄/g VS), which was attributed to the presence of lignocellulosic sawdust and its limited biodegradability. TWS1 showed a moderate level of performance, with an estimated biodegradability of 62.3%, which may have been influenced by the addition of ferric salts and polymeric coagulants during sludge conditioning. In the semi-continuous digestion experiments, reactors that were initiated under relatively high total ammonia nitrogen (TAN) concentrations achieved stable operation within a shorter period, with the acclimation phase reduced by approximately one hydraulic retention time. These trends were supported by the microbial community data, where an increase in Bacillota-associated families, such as Tissierellaceae and Streptococcaceae, was detected along with a clear shift in dominant methanogens from Methanothrix to the more ammonia-tolerant Methanosarcina. Taken together, it is suggested that, when ammonia levels are appropriately managed, mono-digestion of tuna-processing sludges can be operated at a moderate organic loading rate. The process stabilization and energy recovery in nitrogen-rich industrial wastes are closely linked to gradual microbial adaptation rather than immediate improvements in methane yield. Full article

The leather industry generates large amounts of solid waste, creating environmental concerns for the presence of hazardous compounds such as chromium. In fact, conventional disposal practices, including landfill and incineration, promote the formation of hexavalent chromium (Cr⁶⁺) and polluting emissions. This work reviews biochemical and thermochemical processes for the energetic valorization of different leather solid wastes, namely untanned, tanned with chromium or vegetable tanning agents, and post-consumer leather. Thermochemical routes, i.e., pyrolysis, gasification, and hydrothermal treatment (HT), can convert leather waste into energy carriers including bio-oil, syngas, and char, while anaerobic digestion (AD) is a biochemical method used to produce biogas. Particularly, pyrolysis is promising for fuel precursors and chromium stabilization, HT suits wet, raw waste, while gasification enables syngas recovery. In AD, microbial chromium inhibition is mitigated through the co-digestion of degradable substrates. This review takes a waste-type-driven rather than process-driven approach to provide new insights into the conversion of leather solid waste into value-added products, showing that the optimal recycling route depends on the waste characteristics. Moreover, these methods have not yet been directly compared in terms of their energy production performance with regard to leather waste. Future work should improve process conditions, evaluate chromium and finishing additive impacts, and assess scalability. Full article

Elevated levels of total ammonia nitrogen (TAN) are recognized as a primary contributor to acute toxicity in aquatic organisms across freshwater aquaculture and mariculture environments. Existing technologies for TAN removal from wastewater are constrained by complex processes, high energy consumption, and an inability to meet discharge standards in a single step. Conventional electrochemical routes often over-oxidize TAN to nitrate, which undermines the goal of achieving truly harmless wastewater. Herein, we use a three-dimensional (3D) electrochemical system packed with particulate electrodes to realize the “TAN to N₂” in one step. The design exploits a synergistic mechanism in which anodic ·OH and HClO cooperatively oxidize TAN while cathodic sites concurrently reduce nitrate nitrogen, turning NH₄⁺ directly to N₂ without nitrate accumulation. The 3D electrochemical system is particularly suitable for marine aquaculture wastewater, especially when addressing the low TAN concentration characteristic. Results show that the 3D system increased N₂ selectivity from 67.90% to 92.06% while stabilizing wastewater pH within a mildly alkaline window. The system operates in situ, enabling direct recycle of culture water and offering a new technological paradigm for harmless, on-site treatment and resource recovery from mariculture wastewater. Full article

Ammonia stripping has been widely used to recover ammonia nitrogen from biogas slurry; however, the inhibitory effects on biogas production cannot be fully eliminated if ammonia-stripped biogas slurry (ASBS) is recycled back to the high-solid anaerobic digestion (AD) of animal wastes. This study investigated the performance of swine manure AD with recycling of ASBS and confirmed that there was no positive effect on increasing biogas production for ASBS recycling in the swine manure AD system under high solids (15%). The lowest accumulated methane yield was 133.9 mL/g-VS when swine waste was diluted with only raw biogas slurry (RBS), which was 9.2% lower than that of the water group (C₀). Notably, the performance of AD was enhanced by adding rice husk biochar (RHB), waste iron powder (WIP), or their combination with ammonia-stripped biogas slurry (ASBS) reflux in the swine manure AD system. By adding 9.0 g/L of RHB, the biogas yield increased by 21.1%, and the total ammonia concentration (TAN) reduced by 15.1% compared to ASBS reflux alone (C₁). The methane content reached a maximum of 75.2%, which was 12.8% higher than C₁, while the methane yield was 1.5-times higher with the addition of 9.0 g/L of WIP. Correspondingly, the TAN was reduced, while the degradation of volatile fatty acids (VFAs) and total chemical oxygen demand (TCOD) increased. Both WIP and RHB can provide great potential to reuse biogas slurry in AD with a higher biogas yield and organic degradation rate. This approach facilitates source reduction in biogas slurry and nutrient recovery, while providing insights for reducing water consumption in manure treatment processes and enhancing biogas production efficiency. Full article

Ammonia recovery from synthetic thermophilic anaerobic digestate was achieved through Direct Contact Membrane Distillation (DCMD) using hydrophobic flat-sheet membranes under different operating conditions. The influence of temperature gradients (0 °C, 20 °C, 35 °C, and 45 °C) and pH levels of the thermophilic anaerobic sludge (7.8, 8.2, 9, and 12) was investigated. The process utilized a DCMD setup with hydrophobic PTFE membranes of 0.22 µm nominal pore radius, and receiving solutions consisting of deionized water and 1 M H₂SO₄. The best results were obtained with isothermal distillation and high pH levels in the feed. Isothermal distillation at 65 °C (a temperature gradient of 0 °C), with 1 M H₂SO₄ as the receiving solution, and at pH levels 8.2 and 12, yielded NH₃ recoveries of 36.4 ± 1.6% and 100.0 ± 0.1%, respectively. Under the same conditions, the molar fluxes were 0.63 ± 0.01 mol TAN m⁻² h⁻¹ and 1.84 ± 0.01 mol TAN m⁻² h⁻¹, respectively. It is worth noting that some very low depositions on the membrane were detected, leading to changes in the surface morphology, as confirmed by atomic force microscopy. Full article

Shape-memory polymers (SMPs) are a unique class of smart materials capable of recovering their original shape upon external stimuli, with thermoresponsive polyurethane (PU) being one of the most widely studied systems. However, the relatively low mechanical strength, thermal stability, and durability of PU limit its broader functional applications. PU/ND composites containing 0.1–0.5 wt.% ND were fabricated via melt blending and injection molding method. The objective was to evaluate the effect of ND reinforcement on the mechanical, scratch, thermal, rheological, and shape-memory properties. Results show that tensile strength increased up to 114% and Young’s modulus by 11% at 0.5 wt.% ND, while elongation at break decreased due to restricted chain mobility. Hardness improved by 21%, and scratch resistance was significantly enhanced, with the coefficient of friction reduced by 56% at low loads. Thermal stability was improved, with the maximum degradation temperature shifting from 350 °C (pure PU) to 362 °C (0.5 wt.% PU/ND) and char yield increasing by 34%. DSC revealed an increase in glass transition temperature from 65 °C to 68.6 °C. Rheological analysis showed an 89% reduction in damping factor (tan δ), indicating enhanced elasticity. Shape-memory tests confirmed notable improvements in both shape fixity and recovery ratios across successive cycles compared to neat PU, with the highest enhancements observed for the 0.5 wt.% PU/ND nanocomposite—showing up to 7.6% higher fixity and 32% higher recovery than pure PU. These results demonstrate that ND reinforcement effectively strengthens PU while preserving and improving its shape-memory behavior, making the composites promising candidates for high-performance smart materials in sensors, actuators, and aerospace applications. Full article