This study aims to prepare ternary all-solid-waste cementitious materials to completely replace ordinary Portland cement(OPC).Ground granulated blast-furnace slag(GGBS),carbide slag(CS),sulfate solid waste phosphogyps...This study aims to prepare ternary all-solid-waste cementitious materials to completely replace ordinary Portland cement(OPC).Ground granulated blast-furnace slag(GGBS),carbide slag(CS),sulfate solid waste phosphogypsum(PG),electrolytic manganese residue(EMR)and desulfurized gypsum(DG)were used as raw materials to prepare GGBS-PG-CS(GPC),GGBS-EMR-CS(GEC)and GGBS-DG-CS(GDC)ternary all-solid-waste cementitious materials.Macro and microscopic tests were carried out to reveal the mechanical properties and microscopic characteristics,as well as to quantitatively evaluate the environmental and economic benefits.The results show that the optimal ratios of GPC,GEC and GDC are 80:18:2,60:36:4 and 80:18:2,respectively.The corresponding 28 d-unconfined compressive strength(UCS)are 1.62,1.22 and 1.01 times that of OPC,respectively.Carbon emissions and costs per unit strength can be reduced by more than 97%and 57%,respectively.Microscopic analysis shows that the incorporation of sulfate solid waste can synergistically activate GGBS with CS to induce the growth of more needle-like ettringite(AFt),which filled the internal pores and improved the strength of the cementitious material.The better mechanical properties of solidified engineering sediment waste(ESW)also confirm the feasibility of replacing OPC.In summary,this study developed all-solid-waste cementitious materials with excellent mechanical performance,low costs and carbon emissions,which provided a sustainable and economic solution for ESW stabilization.展开更多
The accumulation of contaminated soils and solid waste stockpiles has led to significant resource wastage and environmental pollution.This study investigates a novel solidification/stabilization(S/S)curing agent,named...The accumulation of contaminated soils and solid waste stockpiles has led to significant resource wastage and environmental pollution.This study investigates a novel solidification/stabilization(S/S)curing agent,named ECPG,synthesized from electrolytic manganese residue(EMR),coal gangue(CG),and phosphoric acid,for the treatment of Pb-contaminated soils.The influences of ECPG dosages,CG to EMR ratios,Pb2+and phosphoric acid concentrations,curing age,and durability on the strength development and leaching characteristics of the solidified soils were systematically investigated.Durability tests under different freeze-thaw and wet-dry cycles were also conducted to assess long-term performance.The mechanisms of geopolymerization,S/S,and strength enhancement were elucidated through tests and molecular simulations.The results demonstrated that the optimal CG to EMR ratio was 8:2 with 7 mol/L phosphoric acid,resulting in a peak strength of 5.9 MPa and immobilization rates of 99.7%,99.3%,and 81.5%for Pb,Mn,and NH_(4)^(+)-N after curing for 28 d.Freeze-thaw and wet-dry cycles demonstrated excellent durability,with unconfined compressive strength(UCS)above 85%and Pb leaching value of 0.42 mg/L.Molecular simulations revealed that Pb and Mn were primarily immobilized by adsorption,with ion exchange serving as a secondary mechanism,and a minor fraction resulted in the formation of phosphate precipitates.Conversely,NH_(4)^(+)-N was predominantly immobilized via ion exchange,with a portion forming MgNH_(4)PO_(4)·6H_(2)O and MnNH_(4)PO_(4)·H_(2)O.This study can not only contribute to the advancement of safe disposal and resource reuse of contaminated soil and solid waste,but also offers a theoretical foundation for S/S technology from a multi-scale perspective.展开更多
The remediation of lead-contaminated dredged sediments(LDS)presents significant environmental challenges.This study investigates the solidification/stabilization(S/S)mechanisms of ordinary Portland cement(OPC)modified...The remediation of lead-contaminated dredged sediments(LDS)presents significant environmental challenges.This study investigates the solidification/stabilization(S/S)mechanisms of ordinary Portland cement(OPC)modified with nano-silica(NS)across a continuum from nanoscale interactions to macroscopic performance.For this,a series of macroscopic experiments was conducted to evaluate the mechanical performance and lead-encapsulation efficiency,including unconfined compressive strength(UCS)and toxicity characteristic leaching procedure(TCLP).Microstructural and phase transformations were characterized using X-ray diffraction,thermogravimetric analysis,and scanning electron microscope.Molecular dynamics simulations revealed the interactions between NS-modified cement,calcium silicate hydrates(C-S-H)gel,and Illite,focusing on interaction energies,atomic density distributions and structural changes.Macroscopic analyses demonstrated that increasing NS content from 0%to 8%improved Pb-immobilization rate from 88.7%to 97.6%and enhanced UCS from 764 kPa to 1358 kPa.These improvements were attributed to NS enhancing the microstructural integrity of C-S-H gel and filling pores in samples.Nanoscale simulations elucidated that Pb-stabilization occurs through coordination bonds with oxygen atoms in the C-S-H silicon chains and on Illite surfaces,complemented by the formation of stable Pb_(3)(CO)_(3)(OH)_(2)precipitates.Additionally,the simulations revealed that Ca^(2+)migration from hydration products to mineral surfaces generated substantial repulsive interaction energies,reducing Illite layer dispersion.However,the presence of Pb impeded further Ca^(2+)migration,leading to expansion of the C-S-H gel,which collectively degraded the mechanical properties of the material.Furthermore,wet-dry and freeze-thaw cycles showed that after 10 cycles,UCS and TCLP results still met the United States Environmental Protection Agency standards,confirming long-term durability.This study provides a theoretical foundation for resource utilization of the contaminated sediments and offers a perspective for design of the cement-based curing agents,particularly in addressing variations in pollutant concentrations and environmental conditions,advancing the application of responsive and controlled release curing agents.展开更多
Due to the limited hydration capacity,solidification/stabilization(S/S)with waste concrete powder(WCP)has a low strength.Carbonation can reduce carbon dioxide(CO_(2))emissions and improve strength of lead-contaminated...Due to the limited hydration capacity,solidification/stabilization(S/S)with waste concrete powder(WCP)has a low strength.Carbonation can reduce carbon dioxide(CO_(2))emissions and improve strength of lead-contaminated soil,but its mechanism and environmental behaviors are unclear.In light of this,a comprehensive study was conducted on the compressive strength,lead immobilization,conductivity characteristics,and carbonation mechanism of carbonated Pb-contaminated soils stabilized with WCP compared to calcining 600℃WCP.Results indicated that with carbonation,the compressive strength of the samples was significantly improved at the early stage(1 d),resulting in increased unconfined compressive strength(UCS)by 2.5-5.2 times due to the filling of pores by calcite.It negatively affected the lead immobilization capacity of highly doped(30%)samples,while this effect reversed after 3 d of carbonating due to the reduced alkaline environment.The lead immobilization capacity decreased after 28 d of carbonating due to the cracking of samples and the influence of a lower pH on the solubility of lead-carbonated hydroxide((PbCO_(3))_(2)Pb(OH)_(2)).The water evaporation(saturation<16.8%)led to dry shrinkage cracking and decreased UCS of the samples.Based on this finding,a conductivity model was developed for carbonated and cured samples,accurately predicting changes in saturation levels(R^(2)=0.98).A relationship between conductivity and UCS or lead immobilization capacity was proposed.This research proposed an innovative method for the reduction of CO_(2)emission as well as laid down a theoretical basis for the recovery of WCP and lead-contaminated soils through carbonation.展开更多
Evaluating the stabilized lead(Pb)-contaminated soils through sampling and laboratory testing involves costly and time-consuming processes.Therefore,this study employed a low-cost and non-destructive resistivity tool ...Evaluating the stabilized lead(Pb)-contaminated soils through sampling and laboratory testing involves costly and time-consuming processes.Therefore,this study employed a low-cost and non-destructive resistivity tool to evaluate the Pb-contaminated soils stabilized by electrolytic manganese residue(EMR)-based geopolymer(EG-OPC)from the strength and environmental benefits perspective.First,unconfined compressive strength(UCS)and leaching tests were conducted to study the stabilization effectiveness of EG-OPC.Results indicated that the UCS values of soil(5000 mg/kg of pollutants)stabilized by 20%EG-OPC were 4.87 MPa and 8.13 MPa after 7 d and 60 d of curing,respectively.After 60 d of curing,the Pb concentration in the leachate reached 44 mg/L,far lower than the control group(321 mg/L).Second,soil,pore water,and leachate resistivity(ERS,ERW,and ERL)were measured to establish fitting relationships with strength parameters and pollution risk.The good fitting results(e.g.ERS/ERW versus UCS/secant modulus(E50):correlation coefficient R2 z 0.9,ERS/ERW versus Pb contents:R2 z 0.9,and ERL versus Pb2þconcentration:R2¼0.92)and well used Archie's law(ERS versus ERW:R2>0.9)indicate that the resistivity can be used to evaluate the stabilization effectiveness.Furthermore,the microscopic results revealed two behaviors,demonstrating the reliability of resistivity:(1)with the hydration process,resistivity increases due to a denser structure and lower amounts of free water and Pb ions,and(2)the addition of Pb reduces resistivity due to its inhibition or even destructive effects on cementation and formation of hydration products.展开更多
Actively controllable microswarms have been a rapidly developing research field with appealing characteristics.Autonomous collision-free navigation of microswarms in confined environments is suitable for various appli...Actively controllable microswarms have been a rapidly developing research field with appealing characteristics.Autonomous collision-free navigation of microswarms in confined environments is suitable for various applications,including targeted therapy and delivery.However,several challenges remain unaddressed.First,microswarms possess varying dimensions,and a path planning method suitable to swarms with different dimensions is essential to avoid obstacles.Second,studies on the environment-adaptive navigation of reconfigurable microswarms are limited.Therefore,the planning of the pattern distribution of microswarms based on the local working environment should be examined.This study proposes a deep learning(DL)-based environment-adaptive navigation scheme for swarms.The controller provides reference moving directions for swarms of different sizes in static and dynamic scenarios.Moreover,a pattern-distribution planner was designed to navigate transformable swarms in unstructured environments.To validate the proposed scheme,we applied Fe3O4 nanoparticles swarms as a case study.The proposed scheme enables motion and pattern planning for microrobots of multiple sizes and reconfigurability in various working environments,which could foster a general navigation system for reconfigurable microswarms of different sizes.展开更多
Microlens arrays are the key component in the next generation of 3D imaging system, for it exhibits some good optical properties such as extremely large field of view angles, low aberration and distortion, high tempor...Microlens arrays are the key component in the next generation of 3D imaging system, for it exhibits some good optical properties such as extremely large field of view angles, low aberration and distortion, high temporal resolution and infinite depth of field. Although many fabrication methods or processes are proposed for manufacturing such precision component, however, those methods still need to be improved. In this review, those fabrication methods are categorized into direct and indirect method and compared in detail. Two main challenges in manufacturing microlens array are identified: how to obtain a microlens array with good uniformity in a large area and how to produce the microlens array on a curved surface? In order to effectively achieve control of the geometry of a microlens,indirect methods involving the use of 3D molds and replication technologies are suggested. Further development of ultraprecision machining technology is needed to reduce the surface fluctuation by considering the dynamics of machine tool in tool path planning. Finally, the challenges and opportunities of manufacturing microlens array in industry and academic research are discussed and several principle conclusions are drawn.展开更多
基金support from the Key R&D Program Project of Hubei Province of China(Grant No.2023BCB074)the National Natural Science Foundation of China(Grant No.42307232).
文摘This study aims to prepare ternary all-solid-waste cementitious materials to completely replace ordinary Portland cement(OPC).Ground granulated blast-furnace slag(GGBS),carbide slag(CS),sulfate solid waste phosphogypsum(PG),electrolytic manganese residue(EMR)and desulfurized gypsum(DG)were used as raw materials to prepare GGBS-PG-CS(GPC),GGBS-EMR-CS(GEC)and GGBS-DG-CS(GDC)ternary all-solid-waste cementitious materials.Macro and microscopic tests were carried out to reveal the mechanical properties and microscopic characteristics,as well as to quantitatively evaluate the environmental and economic benefits.The results show that the optimal ratios of GPC,GEC and GDC are 80:18:2,60:36:4 and 80:18:2,respectively.The corresponding 28 d-unconfined compressive strength(UCS)are 1.62,1.22 and 1.01 times that of OPC,respectively.Carbon emissions and costs per unit strength can be reduced by more than 97%and 57%,respectively.Microscopic analysis shows that the incorporation of sulfate solid waste can synergistically activate GGBS with CS to induce the growth of more needle-like ettringite(AFt),which filled the internal pores and improved the strength of the cementitious material.The better mechanical properties of solidified engineering sediment waste(ESW)also confirm the feasibility of replacing OPC.In summary,this study developed all-solid-waste cementitious materials with excellent mechanical performance,low costs and carbon emissions,which provided a sustainable and economic solution for ESW stabilization.
基金supported by the National Key R&D Program of China(Grant No.2022YFC3901204)the National Natural Science Foundation of China(Grant No.42177163)the China Postdoctoral Science Foundation,China(Grant No.2022M723347).
文摘The accumulation of contaminated soils and solid waste stockpiles has led to significant resource wastage and environmental pollution.This study investigates a novel solidification/stabilization(S/S)curing agent,named ECPG,synthesized from electrolytic manganese residue(EMR),coal gangue(CG),and phosphoric acid,for the treatment of Pb-contaminated soils.The influences of ECPG dosages,CG to EMR ratios,Pb2+and phosphoric acid concentrations,curing age,and durability on the strength development and leaching characteristics of the solidified soils were systematically investigated.Durability tests under different freeze-thaw and wet-dry cycles were also conducted to assess long-term performance.The mechanisms of geopolymerization,S/S,and strength enhancement were elucidated through tests and molecular simulations.The results demonstrated that the optimal CG to EMR ratio was 8:2 with 7 mol/L phosphoric acid,resulting in a peak strength of 5.9 MPa and immobilization rates of 99.7%,99.3%,and 81.5%for Pb,Mn,and NH_(4)^(+)-N after curing for 28 d.Freeze-thaw and wet-dry cycles demonstrated excellent durability,with unconfined compressive strength(UCS)above 85%and Pb leaching value of 0.42 mg/L.Molecular simulations revealed that Pb and Mn were primarily immobilized by adsorption,with ion exchange serving as a secondary mechanism,and a minor fraction resulted in the formation of phosphate precipitates.Conversely,NH_(4)^(+)-N was predominantly immobilized via ion exchange,with a portion forming MgNH_(4)PO_(4)·6H_(2)O and MnNH_(4)PO_(4)·H_(2)O.This study can not only contribute to the advancement of safe disposal and resource reuse of contaminated soil and solid waste,but also offers a theoretical foundation for S/S technology from a multi-scale perspective.
基金the supports from the National Natural Science Foundation of China(Grant Nos.42177163 and 42307232)the China Postdoctoral Science Foundation of China(Grant No.2022M723347).
文摘The remediation of lead-contaminated dredged sediments(LDS)presents significant environmental challenges.This study investigates the solidification/stabilization(S/S)mechanisms of ordinary Portland cement(OPC)modified with nano-silica(NS)across a continuum from nanoscale interactions to macroscopic performance.For this,a series of macroscopic experiments was conducted to evaluate the mechanical performance and lead-encapsulation efficiency,including unconfined compressive strength(UCS)and toxicity characteristic leaching procedure(TCLP).Microstructural and phase transformations were characterized using X-ray diffraction,thermogravimetric analysis,and scanning electron microscope.Molecular dynamics simulations revealed the interactions between NS-modified cement,calcium silicate hydrates(C-S-H)gel,and Illite,focusing on interaction energies,atomic density distributions and structural changes.Macroscopic analyses demonstrated that increasing NS content from 0%to 8%improved Pb-immobilization rate from 88.7%to 97.6%and enhanced UCS from 764 kPa to 1358 kPa.These improvements were attributed to NS enhancing the microstructural integrity of C-S-H gel and filling pores in samples.Nanoscale simulations elucidated that Pb-stabilization occurs through coordination bonds with oxygen atoms in the C-S-H silicon chains and on Illite surfaces,complemented by the formation of stable Pb_(3)(CO)_(3)(OH)_(2)precipitates.Additionally,the simulations revealed that Ca^(2+)migration from hydration products to mineral surfaces generated substantial repulsive interaction energies,reducing Illite layer dispersion.However,the presence of Pb impeded further Ca^(2+)migration,leading to expansion of the C-S-H gel,which collectively degraded the mechanical properties of the material.Furthermore,wet-dry and freeze-thaw cycles showed that after 10 cycles,UCS and TCLP results still met the United States Environmental Protection Agency standards,confirming long-term durability.This study provides a theoretical foundation for resource utilization of the contaminated sediments and offers a perspective for design of the cement-based curing agents,particularly in addressing variations in pollutant concentrations and environmental conditions,advancing the application of responsive and controlled release curing agents.
基金the National Natural Science Foundation of China(Grant Nos.42177163 and 42071080)the China Postdoctoral Science Foundation(Grant No.2022M723347).
文摘Due to the limited hydration capacity,solidification/stabilization(S/S)with waste concrete powder(WCP)has a low strength.Carbonation can reduce carbon dioxide(CO_(2))emissions and improve strength of lead-contaminated soil,but its mechanism and environmental behaviors are unclear.In light of this,a comprehensive study was conducted on the compressive strength,lead immobilization,conductivity characteristics,and carbonation mechanism of carbonated Pb-contaminated soils stabilized with WCP compared to calcining 600℃WCP.Results indicated that with carbonation,the compressive strength of the samples was significantly improved at the early stage(1 d),resulting in increased unconfined compressive strength(UCS)by 2.5-5.2 times due to the filling of pores by calcite.It negatively affected the lead immobilization capacity of highly doped(30%)samples,while this effect reversed after 3 d of carbonating due to the reduced alkaline environment.The lead immobilization capacity decreased after 28 d of carbonating due to the cracking of samples and the influence of a lower pH on the solubility of lead-carbonated hydroxide((PbCO_(3))_(2)Pb(OH)_(2)).The water evaporation(saturation<16.8%)led to dry shrinkage cracking and decreased UCS of the samples.Based on this finding,a conductivity model was developed for carbonated and cured samples,accurately predicting changes in saturation levels(R^(2)=0.98).A relationship between conductivity and UCS or lead immobilization capacity was proposed.This research proposed an innovative method for the reduction of CO_(2)emission as well as laid down a theoretical basis for the recovery of WCP and lead-contaminated soils through carbonation.
基金supported by the National Key R&D Program of China(Grant No.2022YFC3901204)the Foundation for Distinguished Young Scholars of Hubei Province,China(Grant No.2021CFA096)the National Natural Science Foundation of China(Grant No.U20A20320).
文摘Evaluating the stabilized lead(Pb)-contaminated soils through sampling and laboratory testing involves costly and time-consuming processes.Therefore,this study employed a low-cost and non-destructive resistivity tool to evaluate the Pb-contaminated soils stabilized by electrolytic manganese residue(EMR)-based geopolymer(EG-OPC)from the strength and environmental benefits perspective.First,unconfined compressive strength(UCS)and leaching tests were conducted to study the stabilization effectiveness of EG-OPC.Results indicated that the UCS values of soil(5000 mg/kg of pollutants)stabilized by 20%EG-OPC were 4.87 MPa and 8.13 MPa after 7 d and 60 d of curing,respectively.After 60 d of curing,the Pb concentration in the leachate reached 44 mg/L,far lower than the control group(321 mg/L).Second,soil,pore water,and leachate resistivity(ERS,ERW,and ERL)were measured to establish fitting relationships with strength parameters and pollution risk.The good fitting results(e.g.ERS/ERW versus UCS/secant modulus(E50):correlation coefficient R2 z 0.9,ERS/ERW versus Pb contents:R2 z 0.9,and ERL versus Pb2þconcentration:R2¼0.92)and well used Archie's law(ERS versus ERW:R2>0.9)indicate that the resistivity can be used to evaluate the stabilization effectiveness.Furthermore,the microscopic results revealed two behaviors,demonstrating the reliability of resistivity:(1)with the hydration process,resistivity increases due to a denser structure and lower amounts of free water and Pb ions,and(2)the addition of Pb reduces resistivity due to its inhibition or even destructive effects on cementation and formation of hydration products.
基金funding support from the National Key R&D Program of China(2023YFB4705600)the Hong Kong Research Grants Council(RGC)with Research Impact Fund(R4015-21)+4 种基金the Research Fellow Scheme(RFS2122-4S03)the Strategic Topics Grant(STG1/E-401/23-N,GRF14300621,GRF14301122,GRF14205823,GRF15206223,and GRF25200424)the Guangdong Basic and Applied Basic Research Foundation Project(2023A1515110709)the Research Institute for Advanced Manufacturing(RIAM)of the Hong Kong Polytechnic University(1-CD9F and 1-CDK3)the Startup Fund Project(1-BE9L)of the Hong Kong Polytechnic University。
文摘Actively controllable microswarms have been a rapidly developing research field with appealing characteristics.Autonomous collision-free navigation of microswarms in confined environments is suitable for various applications,including targeted therapy and delivery.However,several challenges remain unaddressed.First,microswarms possess varying dimensions,and a path planning method suitable to swarms with different dimensions is essential to avoid obstacles.Second,studies on the environment-adaptive navigation of reconfigurable microswarms are limited.Therefore,the planning of the pattern distribution of microswarms based on the local working environment should be examined.This study proposes a deep learning(DL)-based environment-adaptive navigation scheme for swarms.The controller provides reference moving directions for swarms of different sizes in static and dynamic scenarios.Moreover,a pattern-distribution planner was designed to navigate transformable swarms in unstructured environments.To validate the proposed scheme,we applied Fe3O4 nanoparticles swarms as a case study.The proposed scheme enables motion and pattern planning for microrobots of multiple sizes and reconfigurability in various working environments,which could foster a general navigation system for reconfigurable microswarms of different sizes.
基金Supported by Shenzhen Science,Technology and Innovation Commission of China(Grant No.JCYJ20150630115257902)the Research Grants Council of the Hong Kong Special Administrative Region of China(Grant No.ITS/339/13FX)Research Committee of The Hong Kong Polytechnic University,China (Grant No.RUK0)
文摘Microlens arrays are the key component in the next generation of 3D imaging system, for it exhibits some good optical properties such as extremely large field of view angles, low aberration and distortion, high temporal resolution and infinite depth of field. Although many fabrication methods or processes are proposed for manufacturing such precision component, however, those methods still need to be improved. In this review, those fabrication methods are categorized into direct and indirect method and compared in detail. Two main challenges in manufacturing microlens array are identified: how to obtain a microlens array with good uniformity in a large area and how to produce the microlens array on a curved surface? In order to effectively achieve control of the geometry of a microlens,indirect methods involving the use of 3D molds and replication technologies are suggested. Further development of ultraprecision machining technology is needed to reduce the surface fluctuation by considering the dynamics of machine tool in tool path planning. Finally, the challenges and opportunities of manufacturing microlens array in industry and academic research are discussed and several principle conclusions are drawn.
