High-temperature pyrolysis technology can effectively solve the problem of municipal solid waste pollution.However,the pyrolysis gas contains a large amount of CO_(2),which would adversely affect the subsequent utiliz...High-temperature pyrolysis technology can effectively solve the problem of municipal solid waste pollution.However,the pyrolysis gas contains a large amount of CO_(2),which would adversely affect the subsequent utilization.To address this problem,a novel method of co-precipitation modification with Ca,Mg and Zr metals was proposed to improve the CO_(2)capture performance.X-ray diffraction(XRD)patterns and energy dispersive X-ray spectroscopy analysis showed that the two inert supports MgO and CaZrO_(3)were uniformly distributed in the modified calcium-based sorbents.In addition,the XRD results indicated that CaZrO_(3)was produced by the reaction of ZrO_(2)and CaO at high temperatures.The effects of doping ratios,adsorption temperature,calcination temperature,CO_(2)concentration and calcination atmosphere on the adsorption capacity and cycle stability of the modified calcium-based sorbent were studied.The modified calcium-based sorbent achieved the best CO_(2)capture performance when the doping ratio was 10:1:1 with carbonation at 700℃ under 20%CO_(2)/80%N_(2)atmosphere and calcination at 900℃ under100%N_(2)atmosphere.After ten cycles,the average carbonation conversion rate of Ca-10 sorbent was 72%.Finally,the modified calcium-based sorbents successfully reduced the CO_(2)concentration of the pyrolysis gas from 37%to 5%.展开更多
CaO-based sorbent is considered to be a promising candidate for capturing CO_2 at high temperature. However,the adsorption capacity of CaO decreases sharply with the increase of the carbonation/calcination cycles. In ...CaO-based sorbent is considered to be a promising candidate for capturing CO_2 at high temperature. However,the adsorption capacity of CaO decreases sharply with the increase of the carbonation/calcination cycles. In this study, CaO was derived from calcium acetate(CaAc_2), which was doped with different elements(Mg, Al,Ce, Zr and La) to improve the cyclic stability. The carbonation conversion and cyclic stability of sorbents were tested by thermogravimetric analyzer(TGA). The sorbents were characterized by N_2 isothermal adsorption measurements, scanning electron microscopy(SEM) and X-ray diffraction(XRD). The results showed that the cyclic stabilities of all modified sorbents were improved by doping elements, while the carbonation conversions of sorbents in the 1st cycle were not increased by doping different elements. After 22 cycles, the cyclic stabilities of CaO–Al, CaO–Ce and CaO–La were above 96.2%. After 110 cycles, the cyclic stability of CaO–Al was still as high as 87.1%. Furthermore, the carbonation conversion was closely related to the critical time and specific surface area.展开更多
In the present work,the effect of pre-calcination on carbonation conversion and cyclic stability of modi fied CaObased sorbent was investigated by thermogravimetric analyzer(TGA).The modi fied CaO-based sorbents with ...In the present work,the effect of pre-calcination on carbonation conversion and cyclic stability of modi fied CaObased sorbent was investigated by thermogravimetric analyzer(TGA).The modi fied CaO-based sorbents with CaAc_2 as precursor were respectively doped with different elements(Mg,Al,Ce,Zr and La).The speci fic surface area,pore volume and pore size distribution were tested by N_2 isothermal adsorption measurements.The phase compositions of sorbents were characterized by X-ray diffraction(XRD).The results showed that the cyclic stabilities of the sorbents were improved by pre-calcination.The pre-calcination was conducted at 900°C for 5 h in air by the muf fle furnace.With pre-calcination,the cyclic stabilities of sorbents could be as high as 96% after 22 cycles,such as CaO-Al,CaO-Ce and CaO-La.After contact with air,the carbonation conversions of spent sorbents with pre-calcination suddenly increased by about one-sixth due to the change of channel structure by hydration.Both the cyclic stability of sorbent and the durability of reactivation were related to the structural stability of sample,especially the stability of mesopores between 2 nm and 5.5 nm.The present work also provided an easy and low-cost method for reactivating the spent CaO-based sorbents.展开更多
CaO-based heat carriers have shown great prospects for thermochemical energy storage in concentrated solar power systems due to the features such as rich reserves,environmental safety,high energy storage densities and...CaO-based heat carriers have shown great prospects for thermochemical energy storage in concentrated solar power systems due to the features such as rich reserves,environmental safety,high energy storage densities and high operation temperatures.However,the density decay because of sintering and poor direct solar absorption of white CaO based heat carriers are the two main obstacles lying on the way to the realistic applications.This work introduced dark Mn-based inert support into calcium heat carriers,attempting to solve the above problems simultaneously.As an inert support,the finely dispersed Ca_(2)MnO_(4) functioned as the metal framework to resist CaCO_(3)/CaO sintering.Consequently,the cyclic stability of CaO-based heat carriers,resulting in the high energy storage densities of~2000 kJ/kg even over 20 cycles.As a dark material,Ca_(2)MnO_(4) successfully darkened CaO-based heat carriers,thereby greatly enhanced the direct solar absorption.In addition,the granulation of CaO-based heat carriers was also studied.The pellets showed satisfactory attrition resistance with only 9.85 wt% mass loss over 3200 cycles.In general,good physicochemical performance of Mn-doped CaO-based heat carrier endows it with great prospects for solar energy storage.展开更多
Cracks easily generate in concrete at early age owing to the shrinkage deformation.CaO-based expansion agent(CEA)and superabsorbent polymers(SAP)have been extensively used for the mitigation of concrete shrinkage.The ...Cracks easily generate in concrete at early age owing to the shrinkage deformation.CaO-based expansion agent(CEA)and superabsorbent polymers(SAP)have been extensively used for the mitigation of concrete shrinkage.The macroscopic properties of concrete are highly determined by the microstructure.In this study,the influence of CEA and SAP addition on the pore structure evolution of cement paste under different curing temperatures was evaluated via low-field nuclear magnetic resonance spectroscopy.Test results indicated that,in cement paste,a higher CEA content led to a higher porosity and a larger most probable pore diameter(MPPD).Meanwhile,SAP addition increased the porosity and MPPD of CEA cement paste at early age but decreased them after 7 d,and a higher SAP content always brought a higher porosity and MPPD.Furthermore,the addition of SAP led to a lower porosity and MPPD of CEA cement paste than that of plain cement paste after 14 d.Moreover,the porosity and MPPD of CEA cement paste decreased first and subsequently increased as the curing temperature raised.展开更多
It is found that strong basic oxides including Li2O,Na2O,K2O and BaO,which are used to replace a part of CaO in CaO-based fluxes,can lower the melting point and the viscosity and enhance the dephosphorizing ability. T...It is found that strong basic oxides including Li2O,Na2O,K2O and BaO,which are used to replace a part of CaO in CaO-based fluxes,can lower the melting point and the viscosity and enhance the dephosphorizing ability. The mechanism was analysed and the addition of Li2O to CaO based fluxes was recommended.展开更多
B2O3 is selected as fluxing agent of CaO-based ladle refining slag to decrease the melting temperature as well as to improve the speed of slag forming and the refining efficiency. The effects of B2O3 on the melting te...B2O3 is selected as fluxing agent of CaO-based ladle refining slag to decrease the melting temperature as well as to improve the speed of slag forming and the refining efficiency. The effects of B2O3 on the melting temperature of two series of refining slags including the low basicity slags （the mass ratio of CaO/SiO2 is 3--4） and the high basicity slags （the mass ratio of CaO/SiO2 is 5--8.75） were investigated. The slag melting temperature was meas- ured using the hemisphere method. The results indicate that the fluxing action of B2O3 is better than that of CaF2 and A1203. For the CaO-based refining slag with low basicity, the melting temperature is decreased effectively when B2O3 is used to substitute for equal mass of CaF2, Al2O3 and SiO2, respectively. For the CaO-based refining slag with high basicity, when CaF2 is substituted by B2 03, the melting temperature can be decreased remarkably. Espe- cially, when the mass ratios of CaO/Al2O3 and CaO/SiO2 are in the range of 1.1--4.0 and 5.25--8. 0, respectively, the slag melting temperature is lower than 1 300 ℃. Therefore, the 132 03-containing refining slags with high ratios of CaO/Al2O3 and CaO/SiO2 have ultra low melting temperature.展开更多
The CaO-based pellets were fabricated using extrusion-spheronization method for calcium looping thermochemical heat storage under the fluidization.The effects of adhesive,biomass-based pore-forming agent,binder and pa...The CaO-based pellets were fabricated using extrusion-spheronization method for calcium looping thermochemical heat storage under the fluidization.The effects of adhesive,biomass-based pore-forming agent,binder and particle size on the heat storage performance and mechanical property of the CaObased pellets were investigated in a bubbling fluidized bed reactor.The addition of 2%(mass)polyvinylpyrrolidone as an adhesive not only helps granulate,but also improves the heat storage capacity of the pellets.All biomass-templated CaO-based pellets display higher heat storage capacity than biomass-free pellets,indicating that the biomass-based pore-forming agent is beneficial for heat storage under the fluidization.Especially,bagasse-templated pellets show the highest heat storage conversion of 0.61 after 10 cycles.Moreover,Al_(2)O_(3)as a binder for the pellets helps obtain high mechanical strength.The CaO-based pellets doped with 10%(mass)bagasse and 5%(mass)Al_(2)O_(3)reach the highest heat storage density of 1621 kJ·kg^(-1) after 30 cycles and the highest crushing strength of 4.98 N.The microstructure of the bagasse-templated pellets appears more porous than that of biomass-free pellets.The bagassetemplated CaO-based pellets doped with Al_(2)O_(3)seem promising for thermochemical heat storage under the fluidization,owing to the enhanced heat storage capacity,excellent mechanical strength,and simplicity of the synthesis procedure.展开更多
Wastewater plays a crucial role in deteriorating water quality and can significantly affect human health and ecosystems if discharged without proper treatment.Among available treatment methods,adsorption is often cons...Wastewater plays a crucial role in deteriorating water quality and can significantly affect human health and ecosystems if discharged without proper treatment.Among available treatment methods,adsorption is often considered an effective,relatively inexpensive,and environmentally friendly purification technique,but its efficiency depends on the sorbents used.The use of low-cost biosorbents with high adsorption capacity is widely studied.These include various biomaterials such as microalgae,cyanobacteria,fungi,and plant materials.The utilization of different biosorbents derived from plant waste,such as Paulownia wood,aspen,hickory,Ziziphus bark,peach tree shavings,as well as grasses such as red fescue and reed,and Sargassum algae in natural and modified forms,is a crucial research direction.Such studies highlight the potential to address waste issues by repurposing it as biosorbents.Several studies have examined the ability of different biosorbents to treat wastewater and suggested that the physicochemical properties of the material's surface,such as specific surface area,pore size,and pore volume,play a decisive role in adsorption capacity.A quantitative analysis of plant-based biosorbents will significantly aid in developing water treatment systems and achieving optimal adsorption through modifications of their physicochemical properties.Furthermore,the analysis will help understand the relative importance of each physicochemical property in determining adsorption capacity,thereby contributing to the implementation of treatment methods targeting specific pollutants.展开更多
Vertical detection of volatile organic compounds(VOCs)is essential to expend our understanding of the distribution characteristics of VOCs and improve the predictive ability of existing air qualitymodels.In this work,...Vertical detection of volatile organic compounds(VOCs)is essential to expend our understanding of the distribution characteristics of VOCs and improve the predictive ability of existing air qualitymodels.In this work,we report the development of a sorbent tube sampler based on an unmanned aerial vehicle(UAV)platform.Vertical profile measurement of VOCs with a vertical resolution of 25mwas achieved.The sampler consists of five lightweight VOC sorbent tubes and a 5-way solenoid valve,making it available for collecting five atmospheric VOC samples in a single flight with a time response of less than 30min.The samplerweighed∼1.45 kg and had dimensions of 240mm×220mm×100mmwith small penetration loss(<10%)under 4-liter sampling conditions(flow rate of 200 mL/min).Commercialized SUMMA canisters were used as experimental controls to investigate the possible loss of self-made sampler for target compounds in the same sampling process.Comparison experiment on the ground showed that the concentration differences for all VOC species were lower than 0.14μg/m3,proving the good reliability for VOCs measurements using sorbent tube sampler.The UAV platform also incorporated online instruments for meteorological parameters and O_(3) measurement.The sampler was successfully applied to characterize the vertical profiles of VOCs up to 100 m in October 2023 in the Huaihe River Basin of China.The UAV platform and the sorbent tube sampler demonstrate good performance and will be a valuable and reliable tool for vertical VOCs measurement.展开更多
Point source CO_(2) capture(PSCC)is crucial for decarbonizing various industrial sectors,while direct air capture(DAC)holds promise for removing CO_(2) directly from the air.Sorbents play a critical role in both techn...Point source CO_(2) capture(PSCC)is crucial for decarbonizing various industrial sectors,while direct air capture(DAC)holds promise for removing CO_(2) directly from the air.Sorbents play a critical role in both technologies,with their performances,efficiency,cost,etc.,largely depending on which type is used(physical or chemical).Solid amine sorbents(SAS)employed in the chemical adsorption of CO_(2) are suitable for both PSCC and DAC.SAS offer significant advantages over liquid amines such as monoethanolamine(MEA),due to their ability to perform cyclic adsorption–desorption with much lower energy requirement.The environmental concern associated with MEA can be mitigated by SAS.Support materials have a significantly important role in stabilizing amine and enhancing stability and kinetics;varieties of support materials have been screened at a laboratory scale.One promising support material is a silica gel(SG),which is commercially available and attractive for designing cost-effective sorbents for large-scale CO_(2) capture.Various impregnation methods such as physical adsorption and covalent functionalization have been employed to functionalize silica surfaces with amines.This review provided a comprehensive critical analysis of SG-based SAS for CO_(2) capture.We discussed and evaluated them in terms of their adsorption capacity,adsorption,and desorption conditions,and the kinetics involved in these processes.Finally,we proposed a few recommendations for further development of low-cost,lower carbon footprint SAS for large-scale deployment of CO_(2) capture technology.展开更多
A kind of industrial solid waste, i.e., carbide slag, was used as CaO precursor to synthesize CO2 sorbent. The highly reactive synthetic sorbent was prepared from carbide slag, aluminum nitrate hydrate and glycerol wa...A kind of industrial solid waste, i.e., carbide slag, was used as CaO precursor to synthesize CO2 sorbent. The highly reactive synthetic sorbent was prepared from carbide slag, aluminum nitrate hydrate and glycerol water solution by the combustion synthesis method. The results show that the synthetic sorbent exhibits a much higher CO2 capture capacity compared with carbide slag. The CO2 capture capacity and the carbonation conversion of the synthetic sorbent are 0. 38 g/g and 0. 70 after 50 cycles, which are 1.8 and 2. 1 times those of carbide slag. The average carbonation conversion and the CO2 capture efficiency of the synthetic sorbent are higher than those of carbide slag with the same sorbent flow ratios. The required sorbent flow ratios are lower for synthetic sorbent to achieve the same CO2 capture efficiency compared with carbide slag. With the same sorbent flow ratio and CO2 capture efficiency, the energy requirement in calciner for the synthetic sorbent is less than that for carbide slag.展开更多
Under the Paris agreement, China has committed to reducing CO_2 emissions by 60%–65% per unit of GDP by 2030.Since CO_2 emissions from coal-fired power plants currently account for over 30% of the total carbon emissi...Under the Paris agreement, China has committed to reducing CO_2 emissions by 60%–65% per unit of GDP by 2030.Since CO_2 emissions from coal-fired power plants currently account for over 30% of the total carbon emissions in China, it will be necessary to mitigate at least some of these emissions to achieve this goal. Studies by the International Energy Agency(IEA) indicate CCS technology has the potential to contribute 14% of global emission reductions, followed by 40% of higher energy efficiency and 35% of renewable energy, which is considered as the most promising technology to significantly reduce carbon emissions for current coal-fired power plants.Moreover, the announcement of a Chinese national carbon trading market in late 2017 signals an opportunity for the commercial deployment of CO_2 capture technologies.Currently, the only commercially demonstrated technology for post-combustion CO_2 capture technology from power plants is solvent-based absorption. While commercially viable, the costs of deploying this technology are high. This has motivated efforts to develop more affordable alternatives, including advanced solvents, membranes,and sorbent capture systems. Of these approaches, advanced solvents have received the most attention in terms of research and demonstration. In contrast, sorbent capture technology has less attention, despite its potential for much lower energy consumption due to the absence of water in the sorbent. This paper reviews recent progress in the development of sorbent materials modified by amine functionalities with an emphasis on material characterization methods and the effects of operating conditions on performance. The main problems and challenges that need to be overcome to improve the competitiveness of sorbent-based capture technologies are discussed.展开更多
Oxides of silicon, aluminium and calcium are normally dominant minerals during municipal solid waste(MSW)combustion. In flue gas, Si O2, Al2O3 and Ca O all act as sorbents capturing heavy metals(and semi-volatile orga...Oxides of silicon, aluminium and calcium are normally dominant minerals during municipal solid waste(MSW)combustion. In flue gas, Si O2, Al2O3 and Ca O all act as sorbents capturing heavy metals(and semi-volatile organics). To further understand the effect of sorbents during MSW combustion, the effects of Si O2, Al2O3 and Ca O on Cu partitioning were experimentally investigated by the combustion of synthetic MSW in a tubular furnace and their effects on Cu speciation were studied by thermodynamic equilibrium calculations using Chem Kin software. The experiments show that Ca O has the highest Cu sorption efficiency at 900 °C, followed by Al2O3 and Si O2. Thermodynamic equilibrium calculations show that for Cu the addition of Si O2 and Al2O3reduces the amount of liquid Cu Cl, which is more volatile. However, the addition of Ca O has little influence on chemical sorption of Cu, indicating that the sorption of Ca O is resulted from physical sorption.展开更多
In order to reduce the impact of eutrophication caused by agricultural residues （i.e., excess nitrate） in aqueous solution, economic and effective anionic sorbents are required. In this article, we prepared anionic ...In order to reduce the impact of eutrophication caused by agricultural residues （i.e., excess nitrate） in aqueous solution, economic and effective anionic sorbents are required. In this article, we prepared anionic sorbent using wheat straw. Its structural characteristics and adsorption properties for nitrate removal from aqueous solution were investigated. The results indicate that the yield of the prepared anionic sorbent, the total exchange capacity, and the maximum adsorption capacity were 350%, 2.57 mEq/g, and 2.08 mmol/g, respectively. The Freundlich isotherm mode is more suitable than the Langmuir mode and the adsorption process accords with the first order reaction kinetic rate equation. When multiple anions （SO4^2-, H2PO4^-, NO3^-, and NO2^-） were present, the isotherm mode of prepared anionic sorbent for nitrate was consistent with Freundlich mode; however, the capacity of nitrate adsorption was reduced by 50%. In alkaline solutions, about 90% of adsorbed nitrate ions could be desorbed from prepared anionic sorbent. The results of this study confirmed that the wheat straw anionic sorbent can be used as an excellent nitrate sorbent that removes nitrate from aqueous solutions.展开更多
基金the support given by the National Key Research and Development Program of China(2018YFC1901203)Natural Science Foundation of Guangdong Province,China(2021A1515010497)+1 种基金Guangzhou Science and Technology Innovation Development Special FundFundamental Research Funds for the Central Universities(2019MS017)。
文摘High-temperature pyrolysis technology can effectively solve the problem of municipal solid waste pollution.However,the pyrolysis gas contains a large amount of CO_(2),which would adversely affect the subsequent utilization.To address this problem,a novel method of co-precipitation modification with Ca,Mg and Zr metals was proposed to improve the CO_(2)capture performance.X-ray diffraction(XRD)patterns and energy dispersive X-ray spectroscopy analysis showed that the two inert supports MgO and CaZrO_(3)were uniformly distributed in the modified calcium-based sorbents.In addition,the XRD results indicated that CaZrO_(3)was produced by the reaction of ZrO_(2)and CaO at high temperatures.The effects of doping ratios,adsorption temperature,calcination temperature,CO_(2)concentration and calcination atmosphere on the adsorption capacity and cycle stability of the modified calcium-based sorbent were studied.The modified calcium-based sorbent achieved the best CO_(2)capture performance when the doping ratio was 10:1:1 with carbonation at 700℃ under 20%CO_(2)/80%N_(2)atmosphere and calcination at 900℃ under100%N_(2)atmosphere.After ten cycles,the average carbonation conversion rate of Ca-10 sorbent was 72%.Finally,the modified calcium-based sorbents successfully reduced the CO_(2)concentration of the pyrolysis gas from 37%to 5%.
基金Supported by Capture CO_2 and Storage Technology Jointly Studied by USA and China(2013DFB60140-04)Northwest University Graduate Innovative Talent Training Project(YZZ12036)
文摘CaO-based sorbent is considered to be a promising candidate for capturing CO_2 at high temperature. However,the adsorption capacity of CaO decreases sharply with the increase of the carbonation/calcination cycles. In this study, CaO was derived from calcium acetate(CaAc_2), which was doped with different elements(Mg, Al,Ce, Zr and La) to improve the cyclic stability. The carbonation conversion and cyclic stability of sorbents were tested by thermogravimetric analyzer(TGA). The sorbents were characterized by N_2 isothermal adsorption measurements, scanning electron microscopy(SEM) and X-ray diffraction(XRD). The results showed that the cyclic stabilities of all modified sorbents were improved by doping elements, while the carbonation conversions of sorbents in the 1st cycle were not increased by doping different elements. After 22 cycles, the cyclic stabilities of CaO–Al, CaO–Ce and CaO–La were above 96.2%. After 110 cycles, the cyclic stability of CaO–Al was still as high as 87.1%. Furthermore, the carbonation conversion was closely related to the critical time and specific surface area.
基金Supported by Capture CO2 and Storage Technology Jointly Studied by USA and China(2013DFB60140-04)Key Program of National Natural Science Foundation of China(No.21536009)
文摘In the present work,the effect of pre-calcination on carbonation conversion and cyclic stability of modi fied CaObased sorbent was investigated by thermogravimetric analyzer(TGA).The modi fied CaO-based sorbents with CaAc_2 as precursor were respectively doped with different elements(Mg,Al,Ce,Zr and La).The speci fic surface area,pore volume and pore size distribution were tested by N_2 isothermal adsorption measurements.The phase compositions of sorbents were characterized by X-ray diffraction(XRD).The results showed that the cyclic stabilities of the sorbents were improved by pre-calcination.The pre-calcination was conducted at 900°C for 5 h in air by the muf fle furnace.With pre-calcination,the cyclic stabilities of sorbents could be as high as 96% after 22 cycles,such as CaO-Al,CaO-Ce and CaO-La.After contact with air,the carbonation conversions of spent sorbents with pre-calcination suddenly increased by about one-sixth due to the change of channel structure by hydration.Both the cyclic stability of sorbent and the durability of reactivation were related to the structural stability of sample,especially the stability of mesopores between 2 nm and 5.5 nm.The present work also provided an easy and low-cost method for reactivating the spent CaO-based sorbents.
基金Project(2024BAB094)supported by the Key Research and Development Program of Hubei Province,ChinaProject(2024040801020296)supported by the Natural Science Foundation of Wuhan City,ChinaProject(52276113)supported by the National Natural Science Foundation of China。
文摘CaO-based heat carriers have shown great prospects for thermochemical energy storage in concentrated solar power systems due to the features such as rich reserves,environmental safety,high energy storage densities and high operation temperatures.However,the density decay because of sintering and poor direct solar absorption of white CaO based heat carriers are the two main obstacles lying on the way to the realistic applications.This work introduced dark Mn-based inert support into calcium heat carriers,attempting to solve the above problems simultaneously.As an inert support,the finely dispersed Ca_(2)MnO_(4) functioned as the metal framework to resist CaCO_(3)/CaO sintering.Consequently,the cyclic stability of CaO-based heat carriers,resulting in the high energy storage densities of~2000 kJ/kg even over 20 cycles.As a dark material,Ca_(2)MnO_(4) successfully darkened CaO-based heat carriers,thereby greatly enhanced the direct solar absorption.In addition,the granulation of CaO-based heat carriers was also studied.The pellets showed satisfactory attrition resistance with only 9.85 wt% mass loss over 3200 cycles.In general,good physicochemical performance of Mn-doped CaO-based heat carrier endows it with great prospects for solar energy storage.
基金Projects(51878245,U1965105)supported by the National Natural Science Foundation of ChinaProject(2019GSF110006)supported by the Key Research and Development Program of Shandong Province,China+2 种基金Project(2020Z035)supported by the Ningbo 2025 Science and Technology Major Project,ChinaProject(KJ2017B01)supported by the Scientific Research Project of Department of Education of Anhui Province,ChinaProject(2019CEM001)supported by the State Key Laboratory of High Performance Civil Engineering Materials,China。
文摘Cracks easily generate in concrete at early age owing to the shrinkage deformation.CaO-based expansion agent(CEA)and superabsorbent polymers(SAP)have been extensively used for the mitigation of concrete shrinkage.The macroscopic properties of concrete are highly determined by the microstructure.In this study,the influence of CEA and SAP addition on the pore structure evolution of cement paste under different curing temperatures was evaluated via low-field nuclear magnetic resonance spectroscopy.Test results indicated that,in cement paste,a higher CEA content led to a higher porosity and a larger most probable pore diameter(MPPD).Meanwhile,SAP addition increased the porosity and MPPD of CEA cement paste at early age but decreased them after 7 d,and a higher SAP content always brought a higher porosity and MPPD.Furthermore,the addition of SAP led to a lower porosity and MPPD of CEA cement paste than that of plain cement paste after 14 d.Moreover,the porosity and MPPD of CEA cement paste decreased first and subsequently increased as the curing temperature raised.
基金Item Sponsored by National Natural Science Foundation of China(59774015)
文摘It is found that strong basic oxides including Li2O,Na2O,K2O and BaO,which are used to replace a part of CaO in CaO-based fluxes,can lower the melting point and the viscosity and enhance the dephosphorizing ability. The mechanism was analysed and the addition of Li2O to CaO based fluxes was recommended.
基金Item Sponsored by National High Technology Research and Development Program(863 Program)of China(2007AA03Z548)Natural Science Foundation of Jiangsu Province of China(BK2010355)
文摘B2O3 is selected as fluxing agent of CaO-based ladle refining slag to decrease the melting temperature as well as to improve the speed of slag forming and the refining efficiency. The effects of B2O3 on the melting temperature of two series of refining slags including the low basicity slags （the mass ratio of CaO/SiO2 is 3--4） and the high basicity slags （the mass ratio of CaO/SiO2 is 5--8.75） were investigated. The slag melting temperature was meas- ured using the hemisphere method. The results indicate that the fluxing action of B2O3 is better than that of CaF2 and A1203. For the CaO-based refining slag with low basicity, the melting temperature is decreased effectively when B2O3 is used to substitute for equal mass of CaF2, Al2O3 and SiO2, respectively. For the CaO-based refining slag with high basicity, when CaF2 is substituted by B2 03, the melting temperature can be decreased remarkably. Espe- cially, when the mass ratios of CaO/Al2O3 and CaO/SiO2 are in the range of 1.1--4.0 and 5.25--8. 0, respectively, the slag melting temperature is lower than 1 300 ℃. Therefore, the 132 03-containing refining slags with high ratios of CaO/Al2O3 and CaO/SiO2 have ultra low melting temperature.
基金supported by the National Natural Science Foundation of China(51876105)the Fundamental Research Funds of Shandong University(2018JC039)Major Scientific and Technological Innovation Projects of Key Research&Development Program of Shandong Province(2019JZZY020118).
文摘The CaO-based pellets were fabricated using extrusion-spheronization method for calcium looping thermochemical heat storage under the fluidization.The effects of adhesive,biomass-based pore-forming agent,binder and particle size on the heat storage performance and mechanical property of the CaObased pellets were investigated in a bubbling fluidized bed reactor.The addition of 2%(mass)polyvinylpyrrolidone as an adhesive not only helps granulate,but also improves the heat storage capacity of the pellets.All biomass-templated CaO-based pellets display higher heat storage capacity than biomass-free pellets,indicating that the biomass-based pore-forming agent is beneficial for heat storage under the fluidization.Especially,bagasse-templated pellets show the highest heat storage conversion of 0.61 after 10 cycles.Moreover,Al_(2)O_(3)as a binder for the pellets helps obtain high mechanical strength.The CaO-based pellets doped with 10%(mass)bagasse and 5%(mass)Al_(2)O_(3)reach the highest heat storage density of 1621 kJ·kg^(-1) after 30 cycles and the highest crushing strength of 4.98 N.The microstructure of the bagasse-templated pellets appears more porous than that of biomass-free pellets.The bagassetemplated CaO-based pellets doped with Al_(2)O_(3)seem promising for thermochemical heat storage under the fluidization,owing to the enhanced heat storage capacity,excellent mechanical strength,and simplicity of the synthesis procedure.
文摘Wastewater plays a crucial role in deteriorating water quality and can significantly affect human health and ecosystems if discharged without proper treatment.Among available treatment methods,adsorption is often considered an effective,relatively inexpensive,and environmentally friendly purification technique,but its efficiency depends on the sorbents used.The use of low-cost biosorbents with high adsorption capacity is widely studied.These include various biomaterials such as microalgae,cyanobacteria,fungi,and plant materials.The utilization of different biosorbents derived from plant waste,such as Paulownia wood,aspen,hickory,Ziziphus bark,peach tree shavings,as well as grasses such as red fescue and reed,and Sargassum algae in natural and modified forms,is a crucial research direction.Such studies highlight the potential to address waste issues by repurposing it as biosorbents.Several studies have examined the ability of different biosorbents to treat wastewater and suggested that the physicochemical properties of the material's surface,such as specific surface area,pore size,and pore volume,play a decisive role in adsorption capacity.A quantitative analysis of plant-based biosorbents will significantly aid in developing water treatment systems and achieving optimal adsorption through modifications of their physicochemical properties.Furthermore,the analysis will help understand the relative importance of each physicochemical property in determining adsorption capacity,thereby contributing to the implementation of treatment methods targeting specific pollutants.
基金supported by the National Natural Science Foundation of China(Nos.42022051,U21A2028,and 42305124)the Youth Innovation Promotion Association CAS(No.Y202089)the HFIPS Director’s Fund(Nos.BJPY2023A02,YZJJ202101,and YZJJ2023QN01).
文摘Vertical detection of volatile organic compounds(VOCs)is essential to expend our understanding of the distribution characteristics of VOCs and improve the predictive ability of existing air qualitymodels.In this work,we report the development of a sorbent tube sampler based on an unmanned aerial vehicle(UAV)platform.Vertical profile measurement of VOCs with a vertical resolution of 25mwas achieved.The sampler consists of five lightweight VOC sorbent tubes and a 5-way solenoid valve,making it available for collecting five atmospheric VOC samples in a single flight with a time response of less than 30min.The samplerweighed∼1.45 kg and had dimensions of 240mm×220mm×100mmwith small penetration loss(<10%)under 4-liter sampling conditions(flow rate of 200 mL/min).Commercialized SUMMA canisters were used as experimental controls to investigate the possible loss of self-made sampler for target compounds in the same sampling process.Comparison experiment on the ground showed that the concentration differences for all VOC species were lower than 0.14μg/m3,proving the good reliability for VOCs measurements using sorbent tube sampler.The UAV platform also incorporated online instruments for meteorological parameters and O_(3) measurement.The sampler was successfully applied to characterize the vertical profiles of VOCs up to 100 m in October 2023 in the Huaihe River Basin of China.The UAV platform and the sorbent tube sampler demonstrate good performance and will be a valuable and reliable tool for vertical VOCs measurement.
基金financial support from Business Finland 8205/31/2022the Magnus Ehrnrooth Foundation for financial support.
文摘Point source CO_(2) capture(PSCC)is crucial for decarbonizing various industrial sectors,while direct air capture(DAC)holds promise for removing CO_(2) directly from the air.Sorbents play a critical role in both technologies,with their performances,efficiency,cost,etc.,largely depending on which type is used(physical or chemical).Solid amine sorbents(SAS)employed in the chemical adsorption of CO_(2) are suitable for both PSCC and DAC.SAS offer significant advantages over liquid amines such as monoethanolamine(MEA),due to their ability to perform cyclic adsorption–desorption with much lower energy requirement.The environmental concern associated with MEA can be mitigated by SAS.Support materials have a significantly important role in stabilizing amine and enhancing stability and kinetics;varieties of support materials have been screened at a laboratory scale.One promising support material is a silica gel(SG),which is commercially available and attractive for designing cost-effective sorbents for large-scale CO_(2) capture.Various impregnation methods such as physical adsorption and covalent functionalization have been employed to functionalize silica surfaces with amines.This review provided a comprehensive critical analysis of SG-based SAS for CO_(2) capture.We discussed and evaluated them in terms of their adsorption capacity,adsorption,and desorption conditions,and the kinetics involved in these processes.Finally,we proposed a few recommendations for further development of low-cost,lower carbon footprint SAS for large-scale deployment of CO_(2) capture technology.
基金The National Natural Science Foundation of China(No.51376003)
文摘A kind of industrial solid waste, i.e., carbide slag, was used as CaO precursor to synthesize CO2 sorbent. The highly reactive synthetic sorbent was prepared from carbide slag, aluminum nitrate hydrate and glycerol water solution by the combustion synthesis method. The results show that the synthetic sorbent exhibits a much higher CO2 capture capacity compared with carbide slag. The CO2 capture capacity and the carbonation conversion of the synthetic sorbent are 0. 38 g/g and 0. 70 after 50 cycles, which are 1.8 and 2. 1 times those of carbide slag. The average carbonation conversion and the CO2 capture efficiency of the synthetic sorbent are higher than those of carbide slag with the same sorbent flow ratios. The required sorbent flow ratios are lower for synthetic sorbent to achieve the same CO2 capture efficiency compared with carbide slag. With the same sorbent flow ratio and CO2 capture efficiency, the energy requirement in calciner for the synthetic sorbent is less than that for carbide slag.
基金Supported by the National Key Research and Development Program of China(2017YFB0603301)
文摘Under the Paris agreement, China has committed to reducing CO_2 emissions by 60%–65% per unit of GDP by 2030.Since CO_2 emissions from coal-fired power plants currently account for over 30% of the total carbon emissions in China, it will be necessary to mitigate at least some of these emissions to achieve this goal. Studies by the International Energy Agency(IEA) indicate CCS technology has the potential to contribute 14% of global emission reductions, followed by 40% of higher energy efficiency and 35% of renewable energy, which is considered as the most promising technology to significantly reduce carbon emissions for current coal-fired power plants.Moreover, the announcement of a Chinese national carbon trading market in late 2017 signals an opportunity for the commercial deployment of CO_2 capture technologies.Currently, the only commercially demonstrated technology for post-combustion CO_2 capture technology from power plants is solvent-based absorption. While commercially viable, the costs of deploying this technology are high. This has motivated efforts to develop more affordable alternatives, including advanced solvents, membranes,and sorbent capture systems. Of these approaches, advanced solvents have received the most attention in terms of research and demonstration. In contrast, sorbent capture technology has less attention, despite its potential for much lower energy consumption due to the absence of water in the sorbent. This paper reviews recent progress in the development of sorbent materials modified by amine functionalities with an emphasis on material characterization methods and the effects of operating conditions on performance. The main problems and challenges that need to be overcome to improve the competitiveness of sorbent-based capture technologies are discussed.
基金Supported by the National Basic Research Program of China(2011CB201502)
文摘Oxides of silicon, aluminium and calcium are normally dominant minerals during municipal solid waste(MSW)combustion. In flue gas, Si O2, Al2O3 and Ca O all act as sorbents capturing heavy metals(and semi-volatile organics). To further understand the effect of sorbents during MSW combustion, the effects of Si O2, Al2O3 and Ca O on Cu partitioning were experimentally investigated by the combustion of synthetic MSW in a tubular furnace and their effects on Cu speciation were studied by thermodynamic equilibrium calculations using Chem Kin software. The experiments show that Ca O has the highest Cu sorption efficiency at 900 °C, followed by Al2O3 and Si O2. Thermodynamic equilibrium calculations show that for Cu the addition of Si O2 and Al2O3reduces the amount of liquid Cu Cl, which is more volatile. However, the addition of Ca O has little influence on chemical sorption of Cu, indicating that the sorption of Ca O is resulted from physical sorption.
基金Project supported by the Key Science Project of Environmental Protection Foundation of Shandong Government(No.(2006)005).
文摘In order to reduce the impact of eutrophication caused by agricultural residues （i.e., excess nitrate） in aqueous solution, economic and effective anionic sorbents are required. In this article, we prepared anionic sorbent using wheat straw. Its structural characteristics and adsorption properties for nitrate removal from aqueous solution were investigated. The results indicate that the yield of the prepared anionic sorbent, the total exchange capacity, and the maximum adsorption capacity were 350%, 2.57 mEq/g, and 2.08 mmol/g, respectively. The Freundlich isotherm mode is more suitable than the Langmuir mode and the adsorption process accords with the first order reaction kinetic rate equation. When multiple anions （SO4^2-, H2PO4^-, NO3^-, and NO2^-） were present, the isotherm mode of prepared anionic sorbent for nitrate was consistent with Freundlich mode; however, the capacity of nitrate adsorption was reduced by 50%. In alkaline solutions, about 90% of adsorbed nitrate ions could be desorbed from prepared anionic sorbent. The results of this study confirmed that the wheat straw anionic sorbent can be used as an excellent nitrate sorbent that removes nitrate from aqueous solutions.
