摘要：
Understanding the antiseepage and reinforcement mechanisms for pulse grouting remains inadequate at present compared with its engineering applications. To improve the theoretical framework of pulse grouting, a permeation diffusion model based on a Bingham fluid is developed, which incorporates the tortuosity of the slurry diffusion path and spatiotemporal variations in viscosity. The validity of the model is verified through a comparison of the theoretical predictions with the experimental results. The impacts of spatiotemporal viscosity variations and tortuosity on the slurry diffusion mechanism are evaluated via theoretical analysis. The permeation diffusion characteristics of pulse grouting and conventional methods are comparatively simulated and analysed via the COMSOL Multiphysics platform for secondary development. The results show that (i) the maximum relative discrepancy between the theoretical predictions and experimental measurements is less than 30 %, which can be further reduced to under 10 % with increasing grouting pressure, indicating that the theoretical model can offer valuable guidance for the design and implementation of pulse grouting projects. (ii) The spatiotemporal variations in slurry viscosity and the tortuosity of the diffusion path significantly affect permeation diffusion, which intensifies as the grouting pressure and duration increase. The theoretical diffusion distances without considering these two factors are 1.36 ∼ 1.74 times and 1.1 ∼ 1.32 times greater than the experimental results, respectively. (iii) The diffusion morphology of pulse grouting demonstrates a reduced range and a more uniform front under identical conditions, indicating that pulse grouting has significant advantages in the ability to control slurry diffusion compared with conventional methods.
Understanding the antiseepage and reinforcement mechanisms for pulse grouting remains inadequate at present compared with its engineering applications. To improve the theoretical framework of pulse grouting, a permeation diffusion model based on a Bingham fluid is developed, which incorporates the tortuosity of the slurry diffusion path and spatiotemporal variations in viscosity. The validity of the model is verified through a comparison of the theoretical predictions with the experimental results. The impacts of spatiotemporal viscosity variations and tortuosity on the slurry diffusion mechanism are evaluated via theoretical analysis. The permeation diffusion characteristics of pulse grouting and conventional methods are comparatively simulated and analysed via the COMSOL Multiphysics platform for secondary development. The results show that (i) the maximum relative discrepancy between the theoretical predictions and experimental measurements is less than 30 %, which can be further reduced to under 10 % with increasing grouting pressure, indicating that the theoretical model can offer valuable guidance for the design and implementation of pulse grouting projects. (ii) The spatiotemporal variations in slurry viscosity and the tortuosity of the diffusion path significantly affect permeation diffusion, which intensifies as the grouting pressure and duration increase. The theoretical diffusion distances without considering these two factors are 1.36 ∼ 1.74 times and 1.1 ∼ 1.32 times greater than the experimental results, respectively. (iii) The diffusion morphology of pulse grouting demonstrates a reduced range and a more uniform front under identical conditions, indicating that pulse grouting has significant advantages in the ability to control slurry diffusion compared with conventional methods.
摘要：
In the single-stage partial nitritation-anammox process for high-ammonium wastewater treatment, the presence of sufficient biomass with high activity is essential. This study developed an innovative airlift inner-circulation partition bioreactor (AIPBR) with a dual-cylinder structure. During the 362 days’ operation, the AIPBR exhibited robust and stable nitrogen removal performance under diverse influent ammonium spanning from 300 to 1800 mg N/L. Notably, when the influent ammonium was 1820 ± 34 mg N/L, the nitrogen removal rate reached 3.194 ± 0.074 kg N/m³/d, accompanied by removal efficiency of 87.6 ± 1.5%. The unique design of the reactor enabled the formation of dissolved oxygen gradient, which improved the synergy of functional microorganisms by facilitating mass transfer within the sludge. Additionally, it maintained appropriate hydraulic shear in the inner cylinder to support granule formation and simultaneously reduced excessive flow in the outer cylinder to prevent sludge loss. Through the cyclic granulation, the system fostered a symbiotic consortium of flocculent and granular sludge with particle size predominantly distributed within the range of 200–400 μm, which enhanced the activity of microorganisms. These findings highlight the potential of AIPBR as a novel and effective strategy for high-ammonium wastewater treatment.
In the single-stage partial nitritation-anammox process for high-ammonium wastewater treatment, the presence of sufficient biomass with high activity is essential. This study developed an innovative airlift inner-circulation partition bioreactor (AIPBR) with a dual-cylinder structure. During the 362 days’ operation, the AIPBR exhibited robust and stable nitrogen removal performance under diverse influent ammonium spanning from 300 to 1800 mg N/L. Notably, when the influent ammonium was 1820 ± 34 mg N/L, the nitrogen removal rate reached 3.194 ± 0.074 kg N/m³/d, accompanied by removal efficiency of 87.6 ± 1.5%. The unique design of the reactor enabled the formation of dissolved oxygen gradient, which improved the synergy of functional microorganisms by facilitating mass transfer within the sludge. Additionally, it maintained appropriate hydraulic shear in the inner cylinder to support granule formation and simultaneously reduced excessive flow in the outer cylinder to prevent sludge loss. Through the cyclic granulation, the system fostered a symbiotic consortium of flocculent and granular sludge with particle size predominantly distributed within the range of 200–400 μm, which enhanced the activity of microorganisms. These findings highlight the potential of AIPBR as a novel and effective strategy for high-ammonium wastewater treatment.
摘要：
The residual sludge generated from steel wastewater treatment is abundant in iron resource and its recycling has attracted widespread attention. In this study, a novel iron-rich biochar (FSB) with acceptable environmental risk was developed by one-step pyrolysis using steel sludge as raw material, and its adsorption-reduction efficiency and column experiments for hexavalent chromium [Cr(VI)] were determined. The results showed that pyrolysis can effectively reduce the potential environmental risk of iron-rich sludge and effectively enrich iron resources in the biochar matrix. The heavy metal accumulation pattern, potential environmental risk and Cr(VI) adsorption-reduction performance of FSB were affected by pyrolysis temperature, and the optimal performance was achieved at a pyrolysis temperature of 500℃, and the maximum adsorption capacity of FSB pyrolyzed at 500℃ (FSB500) could be as high as 200 mg g −1 . The apparent model fitting showed that Cr(VI) removal by FSB500 was an adsorption-reduction-adsorption process as follows: (i) Cr(VI) was attracted onto FSB500 by electrostatic force; (ii) the oxygen-containing functional groups, persistent free radicals, and endogenous iron on the FSB500 surface acted as the electron donors to convert Cr(VI) to Cr(III); (iii) the released Cr(III) complexed on the FSB500 surface again. In the column experiment, FSB500 showed a high removal capacity of 55.94 mg g −1 under specific conditions. Thus, this study suggests that iron-rich sludge can be prepared into biochar for resource utilization and can be used as an effective alternative for Cr(VI) wastewater treatment.
The residual sludge generated from steel wastewater treatment is abundant in iron resource and its recycling has attracted widespread attention. In this study, a novel iron-rich biochar (FSB) with acceptable environmental risk was developed by one-step pyrolysis using steel sludge as raw material, and its adsorption-reduction efficiency and column experiments for hexavalent chromium [Cr(VI)] were determined. The results showed that pyrolysis can effectively reduce the potential environmental risk of iron-rich sludge and effectively enrich iron resources in the biochar matrix. The heavy metal accumulation pattern, potential environmental risk and Cr(VI) adsorption-reduction performance of FSB were affected by pyrolysis temperature, and the optimal performance was achieved at a pyrolysis temperature of 500℃, and the maximum adsorption capacity of FSB pyrolyzed at 500℃ (FSB500) could be as high as 200 mg g −1 . The apparent model fitting showed that Cr(VI) removal by FSB500 was an adsorption-reduction-adsorption process as follows: (i) Cr(VI) was attracted onto FSB500 by electrostatic force; (ii) the oxygen-containing functional groups, persistent free radicals, and endogenous iron on the FSB500 surface acted as the electron donors to convert Cr(VI) to Cr(III); (iii) the released Cr(III) complexed on the FSB500 surface again. In the column experiment, FSB500 showed a high removal capacity of 55.94 mg g −1 under specific conditions. Thus, this study suggests that iron-rich sludge can be prepared into biochar for resource utilization and can be used as an effective alternative for Cr(VI) wastewater treatment.
摘要：
To address the problems of eutrophication exacerbation in water bodies caused by low carbon-to-nitrogen ratio (C/N) wastewater and the limited nitrogen removal efficiency of conventional constructed wetlands, this study proposes the use of biochar (Corncob biochar YBC, Walnut shell biochar HBC, and Manure biochar FBC) coupled with intermittent aeration technology to enhance nitrogen removal in constructed wetlands. Through the construction of vertical flow wetland systems, hydraulic retention time (HRT = 1-3 d) and influent C/N ratios (1, 3, 5) were regulated, before being combined with material characterization (FTIR/XPS) and microbial analysis (16S rRNA) to reveal the synergistic nitrogen removal mechanisms. HBC achieved efficient NH4+-N adsorption (32.44 mg/L, Langmuir R2 = 0.990) through its high porosity (containing Si-O bonds) and acidic functional groups. Under optimal operating conditions (HRT = 3 d, C/N = 5), the CW-HBC system achieved removal efficiencies of 97.8%, 98.8%, and 79.6% for NH4+-N, TN, and COD, respectively. The addition of biochar shifted the dominant bacterial phylum toward Actinobacteriota (29.79%), with its slow-release carbon source (TOC = 18.5 mg/g) alleviating carbon limitation. Mechanistically, HBC synergistically optimized nitrogen removal pathways through "adsorption-biofilm (bacterial enrichment)-microzone oxygen regulation (pore oxygen gradient)." Based on technical validation, a dual-track institutionalization pathway of "standards-legislation" is proposed: incorporating biochar physicochemical parameters and aeration strategies into multi-level water environment technical standards; converting common mechanisms (such as Si-O adsorption) into legal requirements through legislative amendments; and innovating legislative techniques to balance precision and universality. This study provides an efficient technical solution for low C/N wastewater treatment while constructing an innovative framework for the synergy between technical specifications and legislation, supporting the improvement of watershed ecological restoration systems.
作者机构：
[Wu, Zhiyuan; Meng, Wenkang; Meng, WK] Changsha Univ Sci & Technol, Sch Hydraul & Ocean Engn, Changsha 410114, Peoples R China.;[Wu, Zhiyuan; Meng, Wenkang; Meng, WK] Key Lab Dongting Lake Aquat Ecoenvironm Control &, Changsha 410114, Peoples R China.;[Wu, Zhiyuan; Meng, Wenkang; Meng, WK] Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Peoples R China.;[Li, Jia; Yu, Ching-hao; An, RD; Meng, Wenkang; An, Ruidong; Meng, WK] Sichuan Univ, Coll Water Resource & Hydropower, State Key Lab Hydraul & Mt River Engn, Chengdu 610065, Peoples R China.
通讯机构：
[An, RD ; Meng, WK] S;[Meng, WK ] C;Changsha Univ Sci & Technol, Sch Hydraul & Ocean Engn, Changsha 410114, Peoples R China.;Key Lab Dongting Lake Aquat Ecoenvironm Control &, Changsha 410114, Peoples R China.;Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Peoples R China.
关键词：
Two-phase flow;Level set;Volume of fluid;WENO;Finite volume method
摘要：
The modeling of interfacial two-phase flows involves various fields such as hydraulic engineering, marine engineering, chemical industry, etc., whose difficulty lies in the accurate simulation of the two-phase flow interface. This paper presents a VOF(volume of fluid)-based LS (level set) method with WENO (weighted essentially non-oscillatory) scheme in the finite volume method. The proposed method initializes the LS function by transforming the VOF function, which does not have the characteristics of the distance function yet. Therefore, the next step is to re-distance the transformed LS function by solving the re-initialization equation. For solving the re-initialization equation, the WENO scheme in the finite volume method is employed, providing fifth-order accuracy for the convection term. To validate the proposed VOF-based LS method combined with the WENO scheme, five test cases are presented, including Zalesak's disk, vortex deformation, Rayleigh-Taylor instability, two-dimensional bubble rise, and dam break flow. The numerical results from these interfacial two-phase flow cases demonstrate that the VOF-based LS method with the WENO scheme in the finite volume method can achieve accurate capture of the interface while maintaining excellent mass conservation characteristics.
The modeling of interfacial two-phase flows involves various fields such as hydraulic engineering, marine engineering, chemical industry, etc., whose difficulty lies in the accurate simulation of the two-phase flow interface. This paper presents a VOF(volume of fluid)-based LS (level set) method with WENO (weighted essentially non-oscillatory) scheme in the finite volume method. The proposed method initializes the LS function by transforming the VOF function, which does not have the characteristics of the distance function yet. Therefore, the next step is to re-distance the transformed LS function by solving the re-initialization equation. For solving the re-initialization equation, the WENO scheme in the finite volume method is employed, providing fifth-order accuracy for the convection term. To validate the proposed VOF-based LS method combined with the WENO scheme, five test cases are presented, including Zalesak's disk, vortex deformation, Rayleigh-Taylor instability, two-dimensional bubble rise, and dam break flow. The numerical results from these interfacial two-phase flow cases demonstrate that the VOF-based LS method with the WENO scheme in the finite volume method can achieve accurate capture of the interface while maintaining excellent mass conservation characteristics.
作者机构：
[Risen Yang; Sha Wu; Yangkai Liu; Le Luo; Hong Chen] Key Laboratory of Dongting Lake Aquatic Eco-Environmental Control and Restoration of Hunan Province, School of Hydraulic Engineering, Changsha University of Science & Technology, Changsha 410004, China;[Yanxiao Wei] RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan;[Jianhong Jiang; Qingchang Tang] China Machinery International Engineering Design & Research Institute Co., Ltd., Changsha 410007, China;[Xinying Kong] School of Chemistry and Chemical Engineering, University of South China, Hengyang, Hunan 421001, China;[Elsayed Ali EA] Agricultural Engineering Research Institute (AEnRI), Agricultural Research Center (ARC), Dokki, Giza 256, Egypt
通讯机构：
[Hong Chen] K;Key Laboratory of Dongting Lake Aquatic Eco-Environmental Control and Restoration of Hunan Province, School of Hydraulic Engineering, Changsha University of Science & Technology, Changsha 410004, China
摘要：
To explore the adaptive mechanisms of the partial nitritation-anammox (PNA) process under high salinity stress during kitchen wastewater treatment, focusing on their physiological and molecular responses through metagenomic analysis. An airlift inner-circulation partition bioreactor (AIPBR) was developed, featuring an inner cylinder and a flow guide tube to create distinct oxygen gradients, facilitating the study of microbial adaptation under varying salt conditions. The AIPBR was operated with synthetic wastewater containing ammonium concentrations of 1800 ± 100 mg/L and salinity gradients ranging from 1 to 10 g/L, followed by a fixed salinity period at 6 g/L, with ammonium concentrations approximately 850 mg/L. High-throughput metagenomic analysis revealed shifts in functional genes and metabolic pathways in response to salinity stress. Anammox bacteria adapted by enriching genes involved in the synthesis of osmoprotective compounds and activating energy-producing pathways like the TCA cycle. These adaptations, along with modifications in membrane composition, were essential for sustaining system stability under elevated salinity. Under prolonged high salinity stress, anaerobic ammonium oxidizing (AnAOB) exhibited improved salt tolerance, maintaining a total nitrogen removal efficiency above 85 % and stabilizing after an adaptation phase. The metagenomic data revealed a marked enrichment of genes associated with ion transport, stress response mechanisms, and DNA repair pathways. Changes in microbial community composition favored salt-tolerant species, supporting system stability. These findings highlight the applicability of the developed bioreactor for scaling up the PNA process to handle high-salinity wastewater, providing a promising avenue for sustainable nitrogen removal in challenging environments.
To explore the adaptive mechanisms of the partial nitritation-anammox (PNA) process under high salinity stress during kitchen wastewater treatment, focusing on their physiological and molecular responses through metagenomic analysis. An airlift inner-circulation partition bioreactor (AIPBR) was developed, featuring an inner cylinder and a flow guide tube to create distinct oxygen gradients, facilitating the study of microbial adaptation under varying salt conditions. The AIPBR was operated with synthetic wastewater containing ammonium concentrations of 1800 ± 100 mg/L and salinity gradients ranging from 1 to 10 g/L, followed by a fixed salinity period at 6 g/L, with ammonium concentrations approximately 850 mg/L. High-throughput metagenomic analysis revealed shifts in functional genes and metabolic pathways in response to salinity stress. Anammox bacteria adapted by enriching genes involved in the synthesis of osmoprotective compounds and activating energy-producing pathways like the TCA cycle. These adaptations, along with modifications in membrane composition, were essential for sustaining system stability under elevated salinity. Under prolonged high salinity stress, anaerobic ammonium oxidizing (AnAOB) exhibited improved salt tolerance, maintaining a total nitrogen removal efficiency above 85 % and stabilizing after an adaptation phase. The metagenomic data revealed a marked enrichment of genes associated with ion transport, stress response mechanisms, and DNA repair pathways. Changes in microbial community composition favored salt-tolerant species, supporting system stability. These findings highlight the applicability of the developed bioreactor for scaling up the PNA process to handle high-salinity wastewater, providing a promising avenue for sustainable nitrogen removal in challenging environments.
摘要：
Coral reef islands have been viewed significantly vulnerable to the effects of climate change, especially due to their low elevations when facing sea-level rise ( SLR ) and intensifying storms. Wave-driven flooding and erosion are anticipated to undermining these islands and forcing them to be uninhabitable in a few decades. Although, several existing investigations have tried to tackle the horizontally one-dimensional (1DH) morphological change of reef islands subjected to waves, experimental and numerical investigations on the three-dimensional (3D) island evolution are rare in the literature. Therefore, this study employs a non-hydrostatic phase-resolving model originated from the XBeach tool (XBeach-NH), combined with its sediment transport module. The model was applied to reproduce the published 3D wave basin experiments which used the Fatato Island located at Funafuti Atoll, Tuvalu as the prototype. After model validation, the morphological responses of a more generalized 3D reef island to various climate change indicators, including SLR , increased storm activity and coral growth/degradation were investigated. Simulation results showed that vertical crest accretion, spit rotation, lagoonward island recession, island subaerial area and volume reduction were identified as the island's core responses. Reef islands were also found to have the capacity to adjust vertically to SLR , increased storminess and reef degradation below a threshold. However, their evolution processes can be accelerated as the values of these indicators further increased, eventually resulting in the destruction of the island. The above findings emphasize the pressing necessity to have the island's morphodynamic response integrated into the coastal flood models, thus the island's future persistence and stability could be better resolved.
Coral reef islands have been viewed significantly vulnerable to the effects of climate change, especially due to their low elevations when facing sea-level rise ( SLR ) and intensifying storms. Wave-driven flooding and erosion are anticipated to undermining these islands and forcing them to be uninhabitable in a few decades. Although, several existing investigations have tried to tackle the horizontally one-dimensional (1DH) morphological change of reef islands subjected to waves, experimental and numerical investigations on the three-dimensional (3D) island evolution are rare in the literature. Therefore, this study employs a non-hydrostatic phase-resolving model originated from the XBeach tool (XBeach-NH), combined with its sediment transport module. The model was applied to reproduce the published 3D wave basin experiments which used the Fatato Island located at Funafuti Atoll, Tuvalu as the prototype. After model validation, the morphological responses of a more generalized 3D reef island to various climate change indicators, including SLR , increased storm activity and coral growth/degradation were investigated. Simulation results showed that vertical crest accretion, spit rotation, lagoonward island recession, island subaerial area and volume reduction were identified as the island's core responses. Reef islands were also found to have the capacity to adjust vertically to SLR , increased storminess and reef degradation below a threshold. However, their evolution processes can be accelerated as the values of these indicators further increased, eventually resulting in the destruction of the island. The above findings emphasize the pressing necessity to have the island's morphodynamic response integrated into the coastal flood models, thus the island's future persistence and stability could be better resolved.
摘要：
The classical finite element methods (FEMs) are well-recognized for experiencing significant accuracy degradation at relatively large wavenumbers due to the undesirable dispersion error effect. Moreover, the reliability of FEM solutions is highly dependent on the quality of meshgrids. High-quality meshgrids are indispensable for achieving credible results, especially in regions with steep gradients or complex geometries. However, the generation of such meshgrids can be computationally intensive and time-consuming, particularly for three-dimensional problems with intricate geometries. To address these issues, a modified radial point interpolation meshless method (MRPIM) is proposed to analyzing three-dimensional acoustic problems. This modified method involves a new scheme for selecting interpolation nodes, which facilitates the generation of continuous approximate functions within a single integration cell, thereby reducing integration errors. Our findings indicate that the modified method not only surpasses the original in terms of accuracy but also demonstrates greater efficiency. In addition, the numerical analyses reveal that the computational overheads of this modified method are comparable to the FEMs, suggesting considerable potential for future applications.
The classical finite element methods (FEMs) are well-recognized for experiencing significant accuracy degradation at relatively large wavenumbers due to the undesirable dispersion error effect. Moreover, the reliability of FEM solutions is highly dependent on the quality of meshgrids. High-quality meshgrids are indispensable for achieving credible results, especially in regions with steep gradients or complex geometries. However, the generation of such meshgrids can be computationally intensive and time-consuming, particularly for three-dimensional problems with intricate geometries. To address these issues, a modified radial point interpolation meshless method (MRPIM) is proposed to analyzing three-dimensional acoustic problems. This modified method involves a new scheme for selecting interpolation nodes, which facilitates the generation of continuous approximate functions within a single integration cell, thereby reducing integration errors. Our findings indicate that the modified method not only surpasses the original in terms of accuracy but also demonstrates greater efficiency. In addition, the numerical analyses reveal that the computational overheads of this modified method are comparable to the FEMs, suggesting considerable potential for future applications.
作者机构：
Key Laboratory of Water-Sediment Sciences and Water Disaster Prevention of Hunan Province, Changsha, 410114, China;[Huchen Liu; Xiang Zhong] School of Hydraulic and Ocean Engineering, Changsha University of Science and Technology, Changsha, 410114, China;[Conghao Xu; Yu Yao; Qijia Shi] Key Laboratory of Water-Sediment Sciences and Water Disaster Prevention of Hunan Province, Changsha, 410114, China<&wdkj&>School of Hydraulic and Ocean Engineering, Changsha University of Science and Technology, Changsha, 410114, China
通讯机构：
[Yu Yao] K;Key Laboratory of Water-Sediment Sciences and Water Disaster Prevention of Hunan Province, Changsha, 410114, China<&wdkj&>School of Hydraulic and Ocean Engineering, Changsha University of Science and Technology, Changsha, 410114, China
摘要：
This study presents an experimental and numerical study on the wave attenuation and wave loading characteristics of a two-row artificial reef situated on the forereef slope of a coral reef topography based on a real engineering need. The transmission of the wave energy flux across the artificial reef is found to be very small. An experimental comparison between the wave energy dissipation with and without the artificial reef showed up to 28 % increase in dissipated wave power with the presence of the artificial reef, indicating significant shore protection. The wave energy dissipation is mainly induced by the wave breaking, turbulence, and frictional effects. Numerical results show that under shallow water depths the structure of the artificial reef experiences slamming loads from the highly nonlinear incident wave on the coral reef topography, posing challenges to the stability of the structure. An ad-hoc study on the effect of coral canopy on the artificial reef is conducted using a Darcy-Forchheimer flow model. It is confirmed that the coral canopy is capable of increasing the wave attenuation capability of the artificial reef significantly via more intense wave breaking and stronger dissipation on the reef surface, depending on the thickness of the canopy.
This study presents an experimental and numerical study on the wave attenuation and wave loading characteristics of a two-row artificial reef situated on the forereef slope of a coral reef topography based on a real engineering need. The transmission of the wave energy flux across the artificial reef is found to be very small. An experimental comparison between the wave energy dissipation with and without the artificial reef showed up to 28 % increase in dissipated wave power with the presence of the artificial reef, indicating significant shore protection. The wave energy dissipation is mainly induced by the wave breaking, turbulence, and frictional effects. Numerical results show that under shallow water depths the structure of the artificial reef experiences slamming loads from the highly nonlinear incident wave on the coral reef topography, posing challenges to the stability of the structure. An ad-hoc study on the effect of coral canopy on the artificial reef is conducted using a Darcy-Forchheimer flow model. It is confirmed that the coral canopy is capable of increasing the wave attenuation capability of the artificial reef significantly via more intense wave breaking and stronger dissipation on the reef surface, depending on the thickness of the canopy.
摘要：
Geopolymer concrete is a potential partial substitute for Portland cement (PC) concrete in civil engineering. Understanding chloride-binding behavior and mechanisms in geopolymers is essential for evaluating durability of geopolymer concrete in chloride-rich environments. This study investigated the chloride-binding behavior of metakaolin (MK) geopolymers by examining the influence of chloride ion concentrations, alkali activator concentrations, and pore solution pH levels on their chloride-binding capacities. The correlation between the bound chloride ion content and the geopolymerization degree of MK was analyzed. The experimental results indicated that the binding of MK geopolymer to chloride ions is physical adsorption under the competition of hydroxide ions. Thus when the pH of pore solution decreases from 11.69 to 10.55, the amount of bound chloride increases by 1.95 times. The chloride-binding capacity of the MK geopolymer was primarily determined by the N-A-S-H gel content and the pH of pore solution. Under the same pH levels and chloride ion concentration, the chloride ion content bound per unit N-A-S-H gel remained constant, independent of N-A-S-H gel content. Based on these findings, a new method was proposed to evaluate the geopolymerization degree of MK by mearsuring the chloride-binding capacity of the N-A-S-H gel. The proposed method shows a small margin of error (<5 %) compared to selective acid dissolution analysis, providing valuable insights for research into geopolymer precursor reactions.
Geopolymer concrete is a potential partial substitute for Portland cement (PC) concrete in civil engineering. Understanding chloride-binding behavior and mechanisms in geopolymers is essential for evaluating durability of geopolymer concrete in chloride-rich environments. This study investigated the chloride-binding behavior of metakaolin (MK) geopolymers by examining the influence of chloride ion concentrations, alkali activator concentrations, and pore solution pH levels on their chloride-binding capacities. The correlation between the bound chloride ion content and the geopolymerization degree of MK was analyzed. The experimental results indicated that the binding of MK geopolymer to chloride ions is physical adsorption under the competition of hydroxide ions. Thus when the pH of pore solution decreases from 11.69 to 10.55, the amount of bound chloride increases by 1.95 times. The chloride-binding capacity of the MK geopolymer was primarily determined by the N-A-S-H gel content and the pH of pore solution. Under the same pH levels and chloride ion concentration, the chloride ion content bound per unit N-A-S-H gel remained constant, independent of N-A-S-H gel content. Based on these findings, a new method was proposed to evaluate the geopolymerization degree of MK by mearsuring the chloride-binding capacity of the N-A-S-H gel. The proposed method shows a small margin of error (<5 %) compared to selective acid dissolution analysis, providing valuable insights for research into geopolymer precursor reactions.
期刊：
Journal of Colloid and Interface Science,2025年700(Pt 3):138602 ISSN：0021-9797
通讯作者：
Huang, Binbin
作者机构：
[Mao, Mufan; Lei, Chao] School of Hydraulic Engineering, Changsha University of Science & Technology, Changsha 410114, China;[Mao, Mufan] Key Laboratory of Environmental Biology and Pollution Control, Ministry of Education, College of Environmental Science and Engineering, Hunan University, Changsha 410082, China;[Lei, Xiaojia; Wang, Xuxu] Key Laboratory of Environmental Biology and Pollution Control, Ministry of Education, College of Environmental Science and Engineering, Hunan University, Changsha 410082, China;[Chen, Wenqian] Department of Pharmacy, National University of Singapore, Science Drive 4, Singapore 117560, Singapore;[Xie, Jituo] Center for Collaborative Innovation, Hunan automotive engineering vocational university, Zhuzhou 412000, China
通讯机构：
[Huang, Binbin] K;Key Laboratory of Environmental Biology and Pollution Control, Ministry of Education, College of Environmental Science and Engineering, Hunan University, Changsha 410082, China. Electronic address:
摘要：
Permanganate (PM)-based advanced oxidation process (AOP) is a promising methodology for the efficient degradation of organic pollutants and water purification. Photocatalytic PM activation is an attractive strategy by using clean sustainable solar irradiation, but still faces great challenges in terms of energy source (i.e., ultraviolet light) and catalyst recovery. Here we report a visible light (VL)-driven photocatalytic PM activation strategy as a new platform technology that enables highly efficient degradation of organic pollutants by coupling PM oxidation with photocatalysis. This platform technology is compatible with a wide range of photocatalysts, refractory organic pollutants, pH conditions, and real-water systems. Using micron‑bismuth vanadate (BiVO 4 ) and ciprofloxacin (CIP) as the model catalyst and pollutant, a rapid and complete degradation of CIP was achieved within 7 min with an apparent rate constant of 0.52 min −1 , which was 40 and 9 times higher than those of the PM oxidation and VL-assisted PM oxidation processes, respectively. Physical, theoretical, and in situ spectroscopy investigations showed that the thermodynamically favorable adsorption of PM on BiVO 4 significantly enhanced the separation and utilization of photogenerated electrons, resulting in the concurrent formations of reactive manganese and oxygen species with the former as the primary oxidizing species, and hence contributed to the superior oxidation performance. This strategy achieves a synergy between PM oxidation and photocatalysis that can address their respective critical challenges. Importantly, a horizontal-flow photocatalytic reactor was designed that enabled a continuous degradation of CIP with water treatment capacity of 20 L h −1 under outdoor solar irradiation. This study provides new insight into photocatalytic PM activation and offers a robust AOPs for water purification.
Permanganate (PM)-based advanced oxidation process (AOP) is a promising methodology for the efficient degradation of organic pollutants and water purification. Photocatalytic PM activation is an attractive strategy by using clean sustainable solar irradiation, but still faces great challenges in terms of energy source (i.e., ultraviolet light) and catalyst recovery. Here we report a visible light (VL)-driven photocatalytic PM activation strategy as a new platform technology that enables highly efficient degradation of organic pollutants by coupling PM oxidation with photocatalysis. This platform technology is compatible with a wide range of photocatalysts, refractory organic pollutants, pH conditions, and real-water systems. Using micron‑bismuth vanadate (BiVO 4 ) and ciprofloxacin (CIP) as the model catalyst and pollutant, a rapid and complete degradation of CIP was achieved within 7 min with an apparent rate constant of 0.52 min −1 , which was 40 and 9 times higher than those of the PM oxidation and VL-assisted PM oxidation processes, respectively. Physical, theoretical, and in situ spectroscopy investigations showed that the thermodynamically favorable adsorption of PM on BiVO 4 significantly enhanced the separation and utilization of photogenerated electrons, resulting in the concurrent formations of reactive manganese and oxygen species with the former as the primary oxidizing species, and hence contributed to the superior oxidation performance. This strategy achieves a synergy between PM oxidation and photocatalysis that can address their respective critical challenges. Importantly, a horizontal-flow photocatalytic reactor was designed that enabled a continuous degradation of CIP with water treatment capacity of 20 L h −1 under outdoor solar irradiation. This study provides new insight into photocatalytic PM activation and offers a robust AOPs for water purification.
摘要：
Steel sludge, a byproduct generated from wastewater treatment in the steel industry, has high levels of iron salts and heavy metals, while traditional treatment technologies such as land application, sanitary landfilling, and incineration make resource recovery and utilization challenging. In this study, iron-rich sludge biochar (FSB) was prepared by one-step pyrolysis of iron-rich sludge generated from a steel factory and utilized to activate peroxydisulfate (PS) for tetracycline (TC) removal. Results showed that FSB pyrolyzed at 450 ºC (FSB450) exhibited excellent degradation performance under the optimal conditions (FSB450 dosage of 0.4 g L<sup>−1</sup>, initial solution pH of 3, and PS dosage of 8 mM). In the FSB450/PS system, oxygen-containing functional groups, edge defects, and inherent iron oxides in FSB provided abundant active sites that can facilitate the generation of reactive oxygen species (ROS), including SO<sub>4</sub>˙<sup>−</sup>,<sup>.</sup>OH, O<sub>2</sub>˙<sup>−</sup>, and <sup>1</sup>O<sub>2</sub>, thus accelerating TC degradation by both radical and non-radical processes. Combining with density functional theory (DFT) calculations, the degradation pathways of TC may include demethylation, decarbonylation, dealkylation, dehydroxylation, etc. Meanwhile, the overall toxicity of TC intermediates was reduced after FSB450/PS treatment. Overall, this study provides a novel and feasible approach for the resource utilization of iron-enrich sludge and the treatment of TC wastewater treatment.
作者：
Yang, Shuanglin;Deng, Yiyi;Jiang, Jingyi;Kong, Zhe;Ali, Elsayed A. E.;...
期刊：
Journal of Water Process Engineering,2025年71:107201 ISSN：2214-7144
通讯作者：
Chen, H
作者机构：
[Xu, Ronghua; Chen, Hong; Chen, H; Deng, Yiyi; Yang, Shuanglin; Jiang, Jingyi] Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Peoples R China.;[Kong, Zhe] Suzhou Univ Sci & Technol, Sch Environm Sci & Engn, Suzhou Natl Joint Lab Green & Low Carbon Wastewate, Suzhou 215009, Peoples R China.;[Ali, Elsayed A. E.] Agr Engn Res Inst AEnRI, Agr Res Ctr ARC, POB 256, Giza, Egypt.;[Deng, Zhengyu] China Machinery Int Engn Design & Res Inst Co Ltd, Changsha 410007, Peoples R China.;[Jiang, Wang] Hunan Prov Architectural Design Inst Grp Co Ltd, Changsha 410208, Peoples R China.
通讯机构：
[Chen, H ] C;Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Peoples R China.
关键词：
Sponge cities;Runoff pollution;Bioretention facilities;Soil environmental factors;Microbial community structure
摘要：
To investigate the long-term removal mechanisms of field-scale bioretention facilities using different media for roof runoff treatment, volcanic rock-based (VBF) and zeolite-based bioretention facilities (ZBF) were constructed, and their pollutant removal, soil characteristics, and microbial community dynamics were monitored. It was shown that VBF exhibited higher removal rates for chemical oxygen demand (COD, 84.9 %), ammonia nitrogen (NH 4 + –N, 82.3 %), and total phosphorus (TP, 65.6 %), which can be ascribed to the larger specific surface area and higher iron‑aluminum oxide contents of volcanic rocks. In contrast, ZBF demonstrated superior NO 3 − –N removal efficiency (60.3 %). However, the accumulation of total organic carbon, NH 4 + –N, NO 3 − –N, and TP in VBF was 1.04–1.16 times higher than in ZBF, and redundancy analysis revealed that functional bacteria in VBF were more sensitive to the changes of soil environmental factors (e.g., pH, NH 4 + –N and TP). Furthermore, long-term pollutant inputs resulted in a higher abundance of bacteria involved in organic matter degradation and phosphate solubilization ( Gaiellales , A4b , Vicinamibacteraceae , etc.) in VBF, while ZBF contained a higher abundance of nitrifying and denitrifying bacteria ( Arthrobacter , Roseiflexaceae , KD4-96 , Hyphomicrobium , etc.). These microbial differences contributed to the varying pollutant removal performances between the two facilities, especially for NH 4 + -N and NO 3 − -N. This study provides valuable insights into the long-term pollution control performance and potential media modifications for assembled bioretention facilities.
To investigate the long-term removal mechanisms of field-scale bioretention facilities using different media for roof runoff treatment, volcanic rock-based (VBF) and zeolite-based bioretention facilities (ZBF) were constructed, and their pollutant removal, soil characteristics, and microbial community dynamics were monitored. It was shown that VBF exhibited higher removal rates for chemical oxygen demand (COD, 84.9 %), ammonia nitrogen (NH 4 + –N, 82.3 %), and total phosphorus (TP, 65.6 %), which can be ascribed to the larger specific surface area and higher iron‑aluminum oxide contents of volcanic rocks. In contrast, ZBF demonstrated superior NO 3 − –N removal efficiency (60.3 %). However, the accumulation of total organic carbon, NH 4 + –N, NO 3 − –N, and TP in VBF was 1.04–1.16 times higher than in ZBF, and redundancy analysis revealed that functional bacteria in VBF were more sensitive to the changes of soil environmental factors (e.g., pH, NH 4 + –N and TP). Furthermore, long-term pollutant inputs resulted in a higher abundance of bacteria involved in organic matter degradation and phosphate solubilization ( Gaiellales , A4b , Vicinamibacteraceae , etc.) in VBF, while ZBF contained a higher abundance of nitrifying and denitrifying bacteria ( Arthrobacter , Roseiflexaceae , KD4-96 , Hyphomicrobium , etc.). These microbial differences contributed to the varying pollutant removal performances between the two facilities, especially for NH 4 + -N and NO 3 − -N. This study provides valuable insights into the long-term pollution control performance and potential media modifications for assembled bioretention facilities.
摘要：
The stepped paddy fields (SPFs) are important for food security and sustainable development. The unique spatial structure and complex hydrological processes in this system make it difficult to understand the migration of pollutants. In this study, microplastic pollution was investigated in the water and soil from Ziquejie SPFs, China. Samples were taken according to different stages of rice cultivation, different altitudes, and soil depths. Before rice planting, the average abundance in the water and soil samples was 1.3 ± 1.1 items/L and 292.2 ± 260.8 items/kg, respectively. After rice harvesting, the average abundance in soil increased to 495.37 ± 175.46 items/kg. More microplastics were found in depths of 0–15 cm than that of 15–30 cm, but the difference was not significant. Major microplastics were small (<1 mm) polyethylene (PE) and polypropylene (PP) fibers, with the main color of blue and transparent. The study found that SPFs hindered the migration of microplastics in irrigation water and hydraulic conditions affected the accumulation of microplastics. The edge areas in paddy fields where the water flowed slowly and were prone to vortices made it easier for microplastics to stay. Most of the microplastics accumulated in the upper SPF. After rice harvesting, the overall abundance of microplastics in the SPFs increased. Fibers and fragments exhibited different characteristics in migration. This study attempts to draw attention to the ecological risks caused by microplastic pollution in SPFs, especially in the upper paddy field and the effluent. The results are helpful for the protection of the SPF ecosystem and provide valuable references for future research.
The stepped paddy fields (SPFs) are important for food security and sustainable development. The unique spatial structure and complex hydrological processes in this system make it difficult to understand the migration of pollutants. In this study, microplastic pollution was investigated in the water and soil from Ziquejie SPFs, China. Samples were taken according to different stages of rice cultivation, different altitudes, and soil depths. Before rice planting, the average abundance in the water and soil samples was 1.3 ± 1.1 items/L and 292.2 ± 260.8 items/kg, respectively. After rice harvesting, the average abundance in soil increased to 495.37 ± 175.46 items/kg. More microplastics were found in depths of 0–15 cm than that of 15–30 cm, but the difference was not significant. Major microplastics were small (<1 mm) polyethylene (PE) and polypropylene (PP) fibers, with the main color of blue and transparent. The study found that SPFs hindered the migration of microplastics in irrigation water and hydraulic conditions affected the accumulation of microplastics. The edge areas in paddy fields where the water flowed slowly and were prone to vortices made it easier for microplastics to stay. Most of the microplastics accumulated in the upper SPF. After rice harvesting, the overall abundance of microplastics in the SPFs increased. Fibers and fragments exhibited different characteristics in migration. This study attempts to draw attention to the ecological risks caused by microplastic pollution in SPFs, especially in the upper paddy field and the effluent. The results are helpful for the protection of the SPF ecosystem and provide valuable references for future research.
摘要：
Lead (Pb) toxicity in the environment and plants has emerged as a significant global concern, primarily due to its entry into the human body through the food chain. Several physicochemical and biological techniques are being explored for Pb removal/immobilization. This study explored the efficacy of organic acids—citric acid (CA), acetic acid (AA), and tartaric acid (TA) in mitigating Pb toxicity in plants parts. The treatments included a control (CK, no acid treatment), citric acid (CA) at 0.25 mM (CA0.25) and 0.5 mM (CA0.5), tartaric acid (TA) at 100 mM (TA100) and 200 mM (TA200), and acetic acid (AA) at 100 mM (AA100) and 200 mM (AA200), each replicated in triplicate. Chinese cabbage ( Brassica rapa ) was used as the test crop. Our results revealed significant reductions in Pb concentrations in both plant parts (roots and leaves) as well as in soil following the addition of organic acid. Among the three acid treatments at different concentrations, tartaric acid (TA200) at 200 mM delivered the best results in reducing Pb accumulation in soil-plant system. It notably increased catalase activity (144 μmol g⁻¹), ascorbic acid (12,344 mg L⁻¹), superoxide dismutase (178 U mg⁻¹ protein), and glutathione (98.0 μg g⁻¹ FW), compared to citric and acetic acids treatments. Further, Pearson’s correlation showed a strong negative relationship between Pb content and antioxidant activities, such as catalase, glutathione, and peroxidase (r > 0.90). This study revealed that the application of tartaric acid (TA), particularly at 200 mM through both exogenous and soil treatments, could be an effective strategy to minimize Pb accumulation in polluted areas.
Lead (Pb) toxicity in the environment and plants has emerged as a significant global concern, primarily due to its entry into the human body through the food chain. Several physicochemical and biological techniques are being explored for Pb removal/immobilization. This study explored the efficacy of organic acids—citric acid (CA), acetic acid (AA), and tartaric acid (TA) in mitigating Pb toxicity in plants parts. The treatments included a control (CK, no acid treatment), citric acid (CA) at 0.25 mM (CA0.25) and 0.5 mM (CA0.5), tartaric acid (TA) at 100 mM (TA100) and 200 mM (TA200), and acetic acid (AA) at 100 mM (AA100) and 200 mM (AA200), each replicated in triplicate. Chinese cabbage ( Brassica rapa ) was used as the test crop. Our results revealed significant reductions in Pb concentrations in both plant parts (roots and leaves) as well as in soil following the addition of organic acid. Among the three acid treatments at different concentrations, tartaric acid (TA200) at 200 mM delivered the best results in reducing Pb accumulation in soil-plant system. It notably increased catalase activity (144 μmol g⁻¹), ascorbic acid (12,344 mg L⁻¹), superoxide dismutase (178 U mg⁻¹ protein), and glutathione (98.0 μg g⁻¹ FW), compared to citric and acetic acids treatments. Further, Pearson’s correlation showed a strong negative relationship between Pb content and antioxidant activities, such as catalase, glutathione, and peroxidase (r > 0.90). This study revealed that the application of tartaric acid (TA), particularly at 200 mM through both exogenous and soil treatments, could be an effective strategy to minimize Pb accumulation in polluted areas.
通讯机构：
[Chen, L ] C;Changsha Univ Sci & Technol, Sch Hydraul & Environm Engn, Changsha 410114, Hunan, Peoples R China.
关键词：
Coastal morphodynamics;Sea level rise;XBeach-NH;Spectral waves;Reef island
摘要：
Most existing studies reports that many low-lying reef atoll islands are vulnerable to the sea level rise and increased storminess in the context of global climate change. The positive adjustment of these reef islands to such extreme oceanographic conditions still needs to be further verified. In this study, the open-source XBeach numerical model using its phase-resolving nonhydrostatic module (XB-NH) combined with its morphodynamic module is adopted to investigate the morphodynamic response of reef islands under spectral waves. The model is firstly validated by two published datasets with and without the presence of sandy island located on the reef flat. The model is then applied to examine the effects of a series of incident wave forcing conditions (significant wave height, peak wave period, reef flat water depth) and island initial morphological features (island height, island top width, island beach slope, island location) on the morphodynamic evolution of reef island. Model applications show that two main morphodynamic responses: the elevated reef island crest and the lagoonward migration of the whole island are identified with larger waves and increased water level. One or two of such morphodynamic self-adjustment can be also found for smaller island with steeper beach slope located more closer to the reef edge. These insights highlight the necessity to consider the island morphological features in the coastal management of low-lying reef atoll nations to better resolve their future stability and persistence.
Most existing studies reports that many low-lying reef atoll islands are vulnerable to the sea level rise and increased storminess in the context of global climate change. The positive adjustment of these reef islands to such extreme oceanographic conditions still needs to be further verified. In this study, the open-source XBeach numerical model using its phase-resolving nonhydrostatic module (XB-NH) combined with its morphodynamic module is adopted to investigate the morphodynamic response of reef islands under spectral waves. The model is firstly validated by two published datasets with and without the presence of sandy island located on the reef flat. The model is then applied to examine the effects of a series of incident wave forcing conditions (significant wave height, peak wave period, reef flat water depth) and island initial morphological features (island height, island top width, island beach slope, island location) on the morphodynamic evolution of reef island. Model applications show that two main morphodynamic responses: the elevated reef island crest and the lagoonward migration of the whole island are identified with larger waves and increased water level. One or two of such morphodynamic self-adjustment can be also found for smaller island with steeper beach slope located more closer to the reef edge. These insights highlight the necessity to consider the island morphological features in the coastal management of low-lying reef atoll nations to better resolve their future stability and persistence.
作者机构：
[Chen, Long; Yao, Yu; Sun, Zhenkai; Wang, Hao] Changsha Univ Sci & Technol, Sch Hydraul & Ocean Engn, Changsha 410114, Hunan, Peoples R China.;[Yao, Yu; Chen, Long] Key Lab Water Sediment Sci & Water Disaster Preven, Changsha 410114, Hunan, Peoples R China.;[Chen, Long] Res Inst Innovat Dev Transportat & Energy Integrat, Changsha 410114, Hunan, Peoples R China.;[Chin, Ren-Jie] Univ Tunku Abdul Rahman, Lee Kong Chian Fac Engn & Sci, Dept Civil Engn, Kajang 43000, Malaysia.
通讯机构：
[Chen, L ] C;Changsha Univ Sci & Technol, Sch Hydraul & Ocean Engn, Changsha 410114, Hunan, Peoples R China.
关键词：
Power fluctuation;Tidal turbine fatigue;Seabed bathymetry;Blockage ratio;Wake flow
摘要：
The combination of waves, currents, and seabed bathymetry can result in large hydrodynamic loads that can lead to excessive loading, tidal turbine fatigue and power fluctuations. In this work, a 1:50 scaled tidal stream turbine model is utilized to further the fundamental understanding of tidal turbine behavior with present of seabed bathymetry. The influence of seabed bathymetry proximity on tidal turbines power and loading fluctuations are assessed in terms of spectral density. In the spectral domain of power coefficient, the presence of seabed bathymetry effectively reduces the energy cascade. For thrust coefficient, the frequency decay depicted peaks nearly at the harmonics along the rotor's rotational ( fr ). The coupled effects of seabed bathymetry and blockage ratio were also examined by a transient numerical analysis. The implication of blockage effects is not only to increase the hydrodynamic performance but also shifting the optimum performance TSR to a higher value. The presence of seabed bathymetry resulted in skewed wake flows and the seabed element obstruction is the primary mechanism for reduced performance at close proximity. The results of this study provide recommendations for turbine positioning and fatigue analysis in such flows.
The combination of waves, currents, and seabed bathymetry can result in large hydrodynamic loads that can lead to excessive loading, tidal turbine fatigue and power fluctuations. In this work, a 1:50 scaled tidal stream turbine model is utilized to further the fundamental understanding of tidal turbine behavior with present of seabed bathymetry. The influence of seabed bathymetry proximity on tidal turbines power and loading fluctuations are assessed in terms of spectral density. In the spectral domain of power coefficient, the presence of seabed bathymetry effectively reduces the energy cascade. For thrust coefficient, the frequency decay depicted peaks nearly at the harmonics along the rotor's rotational ( fr ). The coupled effects of seabed bathymetry and blockage ratio were also examined by a transient numerical analysis. The implication of blockage effects is not only to increase the hydrodynamic performance but also shifting the optimum performance TSR to a higher value. The presence of seabed bathymetry resulted in skewed wake flows and the seabed element obstruction is the primary mechanism for reduced performance at close proximity. The results of this study provide recommendations for turbine positioning and fatigue analysis in such flows.
摘要：
High-performance fiber-reinforced concrete (HPFRC) offers exceptional strength, ductility, and durability, making it highly promising for electric power pipe jacking applications. However, limited research exists on the mechanical properties of HPFRC pipes, especially regarding reinforcement schemes. This study bridges this gap by using a combination of three-point testing, analytical calculations, and numerical simulations to investigate the mechanical behavior and performance of HPFRC pipes under various reinforcement configurations. The results show that the load–displacement curve of HPFRC pipes initially follows a linear elastic relationship, but as the load exceeds 200 kN/m, displacement increases and cracks form, with failure occurring at 410 kN/m. HPFRC pipes demonstrate significantly enhanced load-bearing and crack resistance capabilities, with reduced reinforcement and wall thickness compared to traditional materials, maintaining high load-bearing capacity even after damage. The three analysis methods generally align in terms of load-bearing and failure processes, though the analytical method reveals limitations in accurately predicting crack widths. The study also reveals that reinforcement schemes significantly affect the pipes’ structural performance, with double layer and inner layer reinforcement providing superior damage resistance. This study contributes new insights into HPFRC pipe performance and provides a basis for optimizing reinforcement designs in pipe jacking projects.
摘要：
While carbonate sediment transport processes over coral reefs have been extensively investigated in the past decade，very few studies have focused on the morphodynamic response of sandy reef flats to wave action. In this study, a set of innovative wave-flume laboratory experiments was conducted for the first time to investigate the evolution of reef flat based on a barrier reef profile. Various monochromatic wave conditions (incident wave height, incident wave period and initial reef-flat water level) and sediment layer thicknesses were tested. A sand layer was paved on the reef flat to simulate a moveable bed and the reef surface roughness was replicated using an array of cylinders. Subsequently, a phase-resolving non-hydrostatic model (XBeach-NH) was adopted to simulate both the hydrodynamic and morphodynamic processes in the reef environment. A vegetation module was incorporated into Xbeach-NH to represent the rough reef surface. The adopted model was validated against the laboratory dataset for the first time as reported in this study. It was then used to examine the impacts of varying fore-reef slopes, sediment grain sizes and reef surface roughness on the morphodynamic response of sandy reef flats to monochromatic wave action. Model outputs suggested that projected sea-level rise, reduced reef surface roughness and increased storminess due to climate change have profound impacts on the morphodynamic processes on the reef flat thus may eventually contribute the geomorphological sustainability of reef islands.
While carbonate sediment transport processes over coral reefs have been extensively investigated in the past decade，very few studies have focused on the morphodynamic response of sandy reef flats to wave action. In this study, a set of innovative wave-flume laboratory experiments was conducted for the first time to investigate the evolution of reef flat based on a barrier reef profile. Various monochromatic wave conditions (incident wave height, incident wave period and initial reef-flat water level) and sediment layer thicknesses were tested. A sand layer was paved on the reef flat to simulate a moveable bed and the reef surface roughness was replicated using an array of cylinders. Subsequently, a phase-resolving non-hydrostatic model (XBeach-NH) was adopted to simulate both the hydrodynamic and morphodynamic processes in the reef environment. A vegetation module was incorporated into Xbeach-NH to represent the rough reef surface. The adopted model was validated against the laboratory dataset for the first time as reported in this study. It was then used to examine the impacts of varying fore-reef slopes, sediment grain sizes and reef surface roughness on the morphodynamic response of sandy reef flats to monochromatic wave action. Model outputs suggested that projected sea-level rise, reduced reef surface roughness and increased storminess due to climate change have profound impacts on the morphodynamic processes on the reef flat thus may eventually contribute the geomorphological sustainability of reef islands.
关键词：
Atomic hydrogen;Ethylene purification and production;Photocatalytic acetylene hydrogenation;Photosynthesis;Proton coupled electron transfer
摘要：
Ethylene is a basic building block for polymer synthesis, but its purification from petroleum-based processes (e.g., thermo-catalytic acetylene hydrogenation) and its production from coal-based processes (e.g., Fischer-Tropsch synthesis) normally require high temperature, high pressure, and gaseous hydrogen. Here, we report a continuous ethylene photosynthesis approach as a new platform technology that enables highly efficient and selective conversion of acetylene to ethylene in liquid under mild conditions. This platform technology is compatible with a wide range of solvents, catalysts, and hydrogen sources. Using Pd/mpg-C(3)N(4) as the model photocatalyst, a complete conversion of acetylene was achieved with high ethylene selectivity (>93%) under the continuous flow of either a pure acetylene stream or a crude ethylene stream containing acetylene impurity. The process performance remained stable for at least 72 h. Physical, theoretical, and in situ spectroscopy investigations showed that the photocatalytic acetylene hydrogenation follows the proton-coupled electron transfer (PCET) and atomic hydrogen-mediated indirect electron transfer pathways with proton as the hydrogen source. The technoeconomic analysis (TEA) demonstrated that this photocatalytic approach has large profitable margins for both ethylene purification and ethylene production processes. This study provides a green and sustainable technology for both petrochemical (ethylene purification) and coal-chemical (ethylene production) industries.
