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Effects of irradiation on chromium’s behavior in ferritic/martensitic FeCr alloy

Xinfu HE, Wen YANG, Zhehao QU, Sheng FAN

《能源前沿(英文)》 2009年 第3卷 第2期   页码 181-183 doi: 10.1007/s11708-009-0025-x

摘要: The effects of irradiation on chromium performance under different temperatures in Fe-20at%Cr were modeled by modified Marlowe code. Chromium precipitation was observed in FeCr alloy after irradiation; interstitial Chromium atoms are the preferred formation of mixed Fe-Cr dumbbells in the direction of<110>and<111>; interstitial chromium atoms congregated on {111} and {110} plane. The results are compared with experiment observations and are useful to understanding the irradiation performances of FeCr alloy.

关键词: irradiation     Fe-20at%Cr alloy     chromium segregation    

Modeling of solids segregation in circulating fluidized bed boilers

Xuan YAO, Tao WANG, Jia ZHAO, Hairui YANG, Hai ZHANG

《能源前沿(英文)》 2011年 第5卷 第1期   页码 115-119 doi: 10.1007/s11708-010-0103-0

摘要: Segregation always occurs in a circulating fluidized bed (CFB) because of the wide distribution of particle size and density of the bed material. Terminal velocity has a significant influence on solids segregation; thus, it is convenient to describe the segregation tendency using single particle terminal velocity . This paper proposes a segregation model in CFB boilers based on the Cell Model. In each cell along the riser, varied-sized particles have different tendencies toward segregation; finer particles are carried out more easily, while coarser ones tend to sink into the cell. It is assumed that the average terminal velocity , corresponding to the mean particle size in the cell, has a segregation index of = 1.0 as the reference point. The segregation index of particles with higher terminal velocity is lower than 1.0, while that for finer particles is larger than 1.0. The empirical formulae of segregation parameters, namely and , are derived by optimizing experimental data in published literature. The test result of ash size distribution in a 220 t/h CFB boiler validates the reasonableness of the model.

关键词: segregation     model     terminal velocity     circulating fluidized bed (CFB)    

Biogenic palladium prepared by activated sludge microbes for the hexavalent chromium catalytic reduction

Luman Zhou, Chengyang Wu, Yuwei Xie, Siqing Xia

《环境科学与工程前沿(英文)》 2020年 第14卷 第2期 doi: 10.1007/s11783-019-1206-4

摘要: • Pd nanoparticles could be reduced and supported by activated sludge microbes. • The effect of biomass on Pd adsorption by microbes is greater than Pd reduction. • More biomass reduces Pd particle size, which is more dispersed on the cell surface. • When the biomass/Pd add to 6, the catalytic reduction rate of Cr(VI) reaches stable. Palladium, a kind of platinum group metal, owns catalytic capacity for a variety of hydrogenations. In this study, Pd nanoparticles (PdNPs) were generated through enzymatic recovery by microbes of activated sludge at various biomass/Pd, and further used for the Cr(VI) reduction. The results show that biomass had a strong adsorption capacity for Pd(II), which was 17.25 mg Pd/g sludge. The XRD and TEM-EDX results confirmed the existence of PdNPs associated with microbes (bio-Pd). The increase of biomass had little effect on the reduction rate of Pd(II), but it could cause decreasing particle size and shifting location of Pd(0) with the better dispersion degree on the cell surface. In the Cr(VI) reduction experiments, Cr(VI) was first adsorbed on bio-Pd with hydrogen and then reduced using active hydrogen as electron donor. Biomass improved the catalytic activity of PdNPs. When the biomass/Pd (w/w) ratio increased to six or higher, Cr(VI) reduction achieved maximum rate that 50 mg/L of Cr(VI) could be rapidly reduced in one minute.

关键词: Palladium nanoparticles     Activated sludge     Hexavalent chromium    

Stabilization of hexavalent chromium with pretreatment and high temperature sintering in highly contaminated

Haiyan Mou, Wenchao Liu, Lili Zhao, Wenqing Chen, Tianqi Ao

《环境科学与工程前沿(英文)》 2021年 第15卷 第4期 doi: 10.1007/s11783-020-1353-7

摘要: Abstract • Separate reduction and sintering cannot be effective for Cr stabilization. • Combined treatment of reduction and sintering is effective for Cr stabilization. • Almost all the Cr in the reduced soil is residual form after sintering at 1000°C. This study explored the effectiveness and mechanisms of high temperature sintering following pre-reduction with ferric sulfate (FeSO4), sodium sulfide (Na2S), or citric acid (C6H8O7) in stabilizing hexavalent chromium (Cr(VI)) in highly contaminated soil. The soil samples had an initial total Cr leaching of 1768.83 mg/L, and Cr(VI) leaching of 1745.13 mg/L. When FeSO4 or C6H8O7 reduction was followed by sintering at 1000°C, the Cr leaching was reduced enough to meet the Safety Landfill Standards regarding general industrial solid waste. This combined treatment greatly improved the stabilization efficiency of chromium because the reduction of Cr(VI) into Cr(III) decreased the mobility of chromium and made it more easily encapsulated in minerals during sintering. SEM, XRD, TG-DSC, and speciation analysis indicated that when the sintering temperature reached 1000°C, almost all the chromium in soils that had the pre-reduction treatment was transformed into the residual form. At 1000°C, the soil melted and promoted the mineralization of Cr and the formation of new Cr-containing compounds, which significantly decreased subsequent leaching of chromium from the soil. However, without reduction treatment, chromium continued to leach from the soil even after being sintered at 1000°C, possibly because the soil did not fully fuse and because Cr(VI) does not bind with soil as easily as Cr(III).

关键词: Chromium     Heavy contaminated soil     Reduction     Sintering     Stabilization     Speciation    

Temperature segregation and its impact on the quality and performance of asphalt pavements

Minkyum KIM, Pranjal PHALTANE, Louay N. MOHAMMAD, Mostafa ELSEIFI

《结构与土木工程前沿(英文)》 2018年 第12卷 第4期   页码 536-547 doi: 10.1007/s11709-017-0451-5

摘要: Temperature segregation is non-uniform temperature distributionacross the uncompacted asphalt mat during paving operations and mayhave detrimental effects on the quality and performance of asphaltpavements. However, many research studies conducted across the UShave reported mixed observations regarding its effects on the initialquality and long-term performance of asphalt pavements.?The objectiveof this study was to determine the effects of the temperature segregationon the density and mechanical properties of Louisiana asphalt mixtures.Seven asphalt rehabilitation projects across Louisiana were selected.A multi-sensor infrared bar (Pave-IR) system and a hand-held portablethermal camera were used to measure the temperature of asphalt mats.Field core samples were collected from various areas with varyingseverity levels of temperature segregation and tested for the density,fracture resistance (J ) by semi-circular bending(SCB), rut depth by wheel tracking, and dynamic modulus (|E*|) byindirect tension (IDT) devices.?Two distinctive patterns of non-uniformtemperature distribution were observed: a cyclic and irregular temperaturesegregations. Laboratory test results showed that highly temperaturesegregated asphalt pavements (i.e., temperature differentials ≥41.7°C) can have significantly lower densities and the mechanicalproperties than the non-segregated area, especially when the temperaturedifferentials are measured at compaction.

关键词: temperature segregation     temperature differential     pavement density     semi-circular bending     wheel tracking     dynamic modulus    

Concurrent adsorption and reduction of chromium(VI) to chromium(III) using nitrogen-doped porous carbon

《环境科学与工程前沿(英文)》 2022年 第16卷 第5期 doi: 10.1007/s11783-021-1491-6

摘要:

• A high-efficiency N-doped porous carbon adsorbent for Cr(VI) was synthesized.

关键词: Chromium(VI)     Nitrogen-doped porous carbon     Adsorption     Reduction     Loofah sponge    

Enhanced electrokinetic remediation of chromium-contaminated soil using approaching anodes

Shucai LI, Tingting LI, Gang LI, Fengmei LI, Shuhai GUO

《环境科学与工程前沿(英文)》 2012年 第6卷 第6期   页码 869-874 doi: 10.1007/s11783-012-0437-4

摘要: As a new technology used for the cleaning of chromium-contaminated soil, worldwide interest in eletrokinetic (EK) remediation has grown considerably in recent times. However, owing to the fact that chromium exists as both cationic and anionic species in the soil, it is not an efficient method. This paper reports upon a study in which a process using approaching anodes (AAs) was used to enhance the removal efficiency of chromium by eletrokinetics. Two bench-scale experiments to remove chromium from contaminated soil were performed, one using a fixed anode (FA) and the other using AAs. In the AAs experiment, the anode moved toward the cathode by 7 cm every three days. After remediation, soil pH, total chromium, and fractionation of chromium in the soil were determined. The average removal efficiency of total chromium was 11.32% and 18.96% in the FA and AAs experiments, respectively. After remediation, acidic soil conditions throughout the soil were generated through the use of AAs, while 80% of the soil remained neutral or alkalic when using the FA approach. The acidic soil environment and high field intensity in the AAs experiment might have favored chromium desorption, dissolution and dissociation from the soil, plus the mobility of chromium in the soil was also enhanced. The results demonstrate that AAs used in the process of EK remediation can enhance the efficiency of chromium removal from soil.

关键词: approaching anodes     chromium-contaminated soil     electrokinetics     chromium fractionation    

Electroreduction of hexavalent chromium using a porous titanium flow-through electrode and intelligent

《环境科学与工程前沿(英文)》 2023年 第17卷 第8期 doi: 10.1007/s11783-023-1697-x

摘要:

● Titanium-based flow-through electrode achieved high Cr(VI) reduction efficiency.

关键词: Flow-through electrode     Hexavalent chromium     Heavy metals     Neural network     Artificial intelligence    

Hexavalent chromium in drinking water: Chemistry, challenges and future outlook on Sn(II)- and photocatalyst-based

Haizhou Liu, Xuejun Yu

《环境科学与工程前沿(英文)》 2020年 第14卷 第5期 doi: 10.1007/s11783-020-1267-4

摘要: Abstract • Wide occurrence of Cr(VI) in US source drinking water. • A strong dependence of occurrence on groundwater sources. • Elucidate Redox and equilibrium chemistry of Cr(VI). • Sn(II)-based and TiO2-based reductive treatments hold extreme promise. • Key challenges include residual waste, Cr(VI) re-generation and socioeconomic drivers. Chromium (Cr) typically exists in either trivalent and hexavalent oxidation states in drinking water, i.e., Cr(III) and Cr(VI), with Cr(VI) of particular concern in recent years due to its high toxicity and new regulatory standards. This Account presented a critical analysis of the sources and occurrence of Cr(VI) in drinking water in the United States, analyzed the equilibrium chemistry of Cr(VI) species, summarized important redox reaction relevant to the fate of Cr(VI) in drinking water, and critically reviewed emerging Cr(VI) treatment technologies. There is a wide occurrence of Cr(VI) in US source drinking water, with a strong dependence on groundwater sources, mainly due to naturally weathering of chromium-containing aquifers. Challenges regarding traditional Cr(VI) treatment include chemical cost, generation of secondary waste and inadvertent re-generation of Cr(VI) after treatment. To overcome these challenges, reductive Cr(VI) treatment technologies based on the application of stannous tin or electron-releasing titanium dioxide photocatalyst hold extreme promise in the future. To moving forward in the right direction, three key questions need further exploration for the technology implementation, including effective management of residual waste, minimizing the risks of Cr(VI) re-occurrence downstream of drinking water treatment plant, and promote the socioeconomic drivers for Cr(VI) control in the future.

关键词: Chromium     Chemistry     Treatment     Future outlook    

Effects of reducing agent and approaching anodes on chromium removal in electrokinetic soil remediation

Xiaona WEI,Shuhai GUO,Bo WU,Fengmei LI,Gang LI

《环境科学与工程前沿(英文)》 2016年 第10卷 第2期   页码 253-261 doi: 10.1007/s11783-015-0791-0

摘要: A soil remediation method combining in situ reduction of Cr(VI) with approaching anodes electrokinetic (AAs-EK) remediation is proposed. EK experiments were conducted to compare the effect of approaching anodes (AAs) and fixed electrodes (FEs) with and without sodium bisulfite (NaHSO ) as a reducing agent. When NaHSO was added to the soil before EK treatment, 90.3% of the Cr(VI) was reduced to Cr(III). EK experiments showed that the adverse effect of contrasting migration of Cr(III) and Cr(VI) species, which limits the practical application of this technique, was eliminated in the presence of the reducing agent. Furthermore, Tessier fractionation analysis indicated that the reducing agent changed the distribution of the chemical forms of Cr. The AAs-EK method was shown to acidize the soil as the anode moved toward the cathode and this acid front pushed the “focusing” region toward the cathode. After remediation, the pH of the soil was between 1.8 and 5.0 in AAs-EK experiments. The total Cr removal efficiency was 64.4% (except in the “focusing” region) when the reduction reaction was combined with AAs-EK method. We conclude that AAs-EK remediation in the presence of NaHSO is an appropriate method for Cr-contaminated soil.

关键词: chromium     reduction reaction     contrasting migration     approaching anode     electrokinetic    

Improved blending strategy for membrane modification by virtue of surface segregation using surface-tailored

Shuai Liang, Peng Gao, Xiaoqi Gao, Kang Xiao, Xia Huang

《环境科学与工程前沿(英文)》 2016年 第10卷 第6期 doi: 10.1007/s11783-016-0875-5

摘要: Two types of amphiphilic nanoparticles were prepared via silanization reaction. Amphiphilic nanoparticles tend to protrude from membrane matrix by segregation. Blending with amphiphilic nanoparticles further enhances membrane hydrophilicity. Excessive silanization cause adverse effect on blending efficiency. Membrane modification is one of the most feasible and effective solutions to membrane fouling problem which tenaciously hampered the further augmentation of membrane separation technology. Blending modification with nanoparticles (NPs), owing to the convenience of being incorporated in established membrane production lines, possesses an advantageous viability in practical applications. However, the existing blending strategy suffers from a low utilization efficiency due to NP encasement by membrane matrix. The current study proposed an improved blending modification approach with amphiphilic NPs (aNPs), which were prepared through silanization using 3-(Trimethoxysilyl)propyl methacrylate (TMSPMA) as coupling agents and ZnO or SiO as pristine NPs (pNPs), respectively. The Fourier transform infrared and X-ray photoelectron spectroscopy analyses revealed the presence of appropriate organic components in both the ZnO and SiO aNPs, which verified the success of the silanization process. As compared with the pristine and conventional pNP-blended membranes, both the ZnO aNP-blended and SiO aNP-blended membranes with proper silanization (100% and 200% w/w) achieved a significantly increased blending efficiency with more NPs scattering on the internal and external membrane surfaces under scanning electron microscope observation. This improvement contributed to the increase of membrane hydrophilicity. Nevertheless, an extra dosage of the TMSPMA led to an encasement of NPs, thereby adversely affecting the properties of the resultant membranes. On the basis of all the tests, 100% (w/w) was selected as the optimum TMSPMA dosage for blending modification for both the ZnO and SiO types.

关键词: Membrane modification     Nanoparticle     Hydrophilic     Amphiphilic     Blending    

from metagenomic, metatranscriptomic, and molecular ecological network analyses into the effects of chromium

Quan Zheng, Minglu Zhang, Tingting Zhang, Xinhui Li, Minghan Zhu, Xiaohui Wang

《环境科学与工程前沿(英文)》 2020年 第14卷 第4期 doi: 10.1007/s11783-020-1239-8

摘要: Abstract • Cr NPs significantly promoted the denitrifying process and phosphorus removal. • The quantities of denitrifying and phosphorus genes greatly increased. • The transcription of denitrifying and phosphorus genes greatly increased. • The networks associated with nitrogen and phosphorus removal became complicated. • Cr NPs decreased some genera related to GAOs. The objectives of this study were to investigate the influence of chromium nanoparticles (Cr NPs) on the nitrogen and phosphorus removal performance and the bacterial structures of an activated sludge (AS) system. Also, we through molecular ecological networks (MENs) discussed the bacterial interactions. At last we researched the change of the functional genes and their expression patterns related to nitrogen and phosphorus removal in an AS system. The results showed that long-term exposure to 1 mg/L Cr NPs significantly promoted the denitrifying process and phosphorus removal in the AS system. The relative abundance of denitrifying and phosphorus removal microorganisms, such as Denitratisoma, Thauera, Dechloromonas, and Defluviicoccus, increased significantly. Candidatus Accumulibacter, well-known as polyphosphate-accumulating organisms (PAOs), increased significantly; the relative abundance of Candidatus Competibacter, known as glycogen-accumulating organisms (GAOs), decreased significantly. Furthermore, metagenomic and metatranscriptomic analysis revealed that most of the genera related to denitrifying and phosphorus removal had greatly increased, according to the quantities of denitrifying and phosphorus genes, and the corresponding transcription likewise greatly increased. Lastly, MENs analysis showed that although the overall network became smaller and looser in the presence of Cr NPs, the microbial connections among members related to nitrogen and phosphorus removal were enhanced. The abundance increases of denitrifiers and PAOs, and their increased transcription of functional genes, together with the enhanced interactions may be associated with the promotion of the denitrifying process and phosphorus removal.

关键词: Chromium nanoparticles (Cr NPs)     Metagenomic analysis     Metatranscriptomic analysis     Molecular ecological networks (MENs)     Nitrogen and phosphorus removal    

Reduction of hexavalent chromium with scrap iron in a fixed bed reactor

Yin WANG, Xuejiang WANG, Xin WANG, Mian LIU, Siqing XIA, Daqiang YIN, Yalei ZHANG, Jianfu ZHAO

《环境科学与工程前沿(英文)》 2012年 第6卷 第6期   页码 761-769 doi: 10.1007/s11783-012-0413-z

摘要: The reduction of hexavalent chromium by scrap iron was investigated in continuous long-term fixed bed system. The effects of pH, empty bed contact time (EBCT), and initial Cr(VI) concentration on Cr(VI) reduction were studied. The results showed that the pH, EBCT, and initial Cr(VI) concentration significantly affected the reduction capacity of scrap iron. The reduction capacity of scrap iron were 4.56, 1.51, and 0.57 mg Cr(VI)·g Fe at pH 3, 5, and 7 (initial Cr(VI) concentration 4 mg·L , EBCT 2 min, and temperature 25°C), 0.51, 1.51, and 2.85 mg Cr(VI)·g Fe at EBCTs of 0.5, 2.0, and 6.0 min (initial Cr(VI) concentration 4 mg·L , pH 5, and temperature 25°C), and 2.99, 1.51, and 1.01 mg Cr(VI)·g Fe at influent concentrations of 1, 4, and 8 mg·L (EBCT 2 min, pH 5, and temperature 25°C), respectively. Fe(total) concentration in the column effluent continuously decreased in time, due to a decrease in time of the iron corrosion rate. The fixed bed reactor can be readily used for the treatment of drinking water containing low amounts of Cr(VI) ions, although the hardness and humic acid in water may shorten the lifetime of the reactor, the reduction capacity of scrap iron still achieved 1.98 mg Cr ·g Fe. Scanning electron microscope equipped with energy dispersion spectrometer and X-ray diffraction were conducted to examine the surface species of the scrap iron before and after its use. In addition to iron oxides and hydroxide species, iron-chromium complex was also observed on the reacted scrap iron.

关键词: hexavalent chromium     scrap iron     reduction capacity     drinking water    

Chromium phytoextraction and physiological responses of the hyperaccumulator Swartz to plant growth-promoting

《环境科学与工程前沿(英文)》 2023年 第17卷 第1期 doi: 10.1007/s11783-023-1609-0

摘要:

● Improved Cr phytoextration efficiency was achieved by B. cereus inoculation.

关键词: Hexavalent chromium     Hyperaccumulator     Rhizobacteria     Leersia hexandra Swartz     Bacillus cereus     Consortia    

Kinetics of hexavalent chromium reduction by iron metal

QIAN Huijing, WU Yanjun, LIU Yong, XU Xinhua

《环境科学与工程前沿(英文)》 2008年 第2卷 第1期   页码 51-56 doi: 10.1007/s11783-008-0010-3

摘要: The kinetics of Cr(VI) reduction to Cr(III) by metallic iron (Fe) was studied in batch reactors for a range of reactant concentrations, pH and temperatures. Nearly 86.8% removal efficiency for Cr(VI) was achieved when Fe concentration was 6 g/L (using commercial iron powder (< 200 mesh) in 120 min). The reduction of hexavalent chromium took place on the surface of the iron particles following pseudo-first order kinetics. The rate of Cr(VI) reduction increased with increasing Fe addition and temperature but inversely with initial pH. The pseudo-first-order rate coefficients () were determined as 0.0024, 0.010, 0.0268 and 0.062 8 min when iron powder dosages were 2, 6, 10 and 14 g/L at 25°C and pH 5.5, respectively. According to the Arrehenius equation, the apparent activation energy of 26.5 kJ/mol and pre-exponential factor of 3 330 min were obtained at the temperature range of 288–308 K. Different Fe types were compared in this study. The reactivity was in the order starch-stabilized Fe nanoparticles > Fe nano-particles > Fe powder > Fe filings. Electrochemical analysis of the reaction process showed that Cr(III) and Fe(III) hydroxides should be the dominant final products.

关键词: Different     process     surface     Electrochemical analysis     concentration    

标题 作者 时间 类型 操作

Effects of irradiation on chromium’s behavior in ferritic/martensitic FeCr alloy

Xinfu HE, Wen YANG, Zhehao QU, Sheng FAN

期刊论文

Modeling of solids segregation in circulating fluidized bed boilers

Xuan YAO, Tao WANG, Jia ZHAO, Hairui YANG, Hai ZHANG

期刊论文

Biogenic palladium prepared by activated sludge microbes for the hexavalent chromium catalytic reduction

Luman Zhou, Chengyang Wu, Yuwei Xie, Siqing Xia

期刊论文

Stabilization of hexavalent chromium with pretreatment and high temperature sintering in highly contaminated

Haiyan Mou, Wenchao Liu, Lili Zhao, Wenqing Chen, Tianqi Ao

期刊论文

Temperature segregation and its impact on the quality and performance of asphalt pavements

Minkyum KIM, Pranjal PHALTANE, Louay N. MOHAMMAD, Mostafa ELSEIFI

期刊论文

Concurrent adsorption and reduction of chromium(VI) to chromium(III) using nitrogen-doped porous carbon

期刊论文

Enhanced electrokinetic remediation of chromium-contaminated soil using approaching anodes

Shucai LI, Tingting LI, Gang LI, Fengmei LI, Shuhai GUO

期刊论文

Electroreduction of hexavalent chromium using a porous titanium flow-through electrode and intelligent

期刊论文

Hexavalent chromium in drinking water: Chemistry, challenges and future outlook on Sn(II)- and photocatalyst-based

Haizhou Liu, Xuejun Yu

期刊论文

Effects of reducing agent and approaching anodes on chromium removal in electrokinetic soil remediation

Xiaona WEI,Shuhai GUO,Bo WU,Fengmei LI,Gang LI

期刊论文

Improved blending strategy for membrane modification by virtue of surface segregation using surface-tailored

Shuai Liang, Peng Gao, Xiaoqi Gao, Kang Xiao, Xia Huang

期刊论文

from metagenomic, metatranscriptomic, and molecular ecological network analyses into the effects of chromium

Quan Zheng, Minglu Zhang, Tingting Zhang, Xinhui Li, Minghan Zhu, Xiaohui Wang

期刊论文

Reduction of hexavalent chromium with scrap iron in a fixed bed reactor

Yin WANG, Xuejiang WANG, Xin WANG, Mian LIU, Siqing XIA, Daqiang YIN, Yalei ZHANG, Jianfu ZHAO

期刊论文

Chromium phytoextraction and physiological responses of the hyperaccumulator Swartz to plant growth-promoting

期刊论文

Kinetics of hexavalent chromium reduction by iron metal

QIAN Huijing, WU Yanjun, LIU Yong, XU Xinhua

期刊论文