Effect of Ca/Si ratio on the properties of steel slag and deactivated ZSM-5 autoclaved aerated concrete

In this study, the feasibility of the complete replacement of lime by steel slag (SS) as a calcium material with deactivated ZSM-5 for the preparation of autoclaved aerated concrete (AAC) was investigated. The effects of the Ca/Si ratio on the foaming effect, bulk density and mechanical strength, mineral composition, pore structure and microstructure were studied. The results show that the increase of the Ca/Si ratio enhanced the early foaming effect. AAC with an optimum Ca/Si ratio of 0.92 had a compressive strength and bulk density of 3.1 MPa and 535 kg/m³, respectively, meeting the national standards (GB/T 11968-2020) of grade A2.5 and B05. The increase of the Ca/Si ratio significantly reduced the number of pores with a pore size greater than 60 μm. In addition, X-ray diffraction (XRD) and scanning electron microscopy (SEM) results show that an elevated Ca/Si ratio will change the shape and crystallinity of tobermorite.     

催化褪色光度法测定粉煤灰中痕量钼

在pH11.0的Na2CO3 NaHCO3缓冲溶液中,痕量钼(Ⅵ)对H2O2氧化偶氮胭脂红B的褪色反应具有强烈的催化作用,据此建立了一种测定痕量钼(Ⅵ)的催化光度法的新方法。方法的检出限为2.04×10-2μg/L,线性范围为0～6.0μg/L,该法已应用于粉煤灰中痕量钼的测定。     

水冷壁气流床气化炉灰渣结构分析

在管式电炉还原性气氛下,对煤灰进行1 300℃和1 400℃的高温热处理。同时,在小型膜式水冷壁气流床气化炉热模装置中进行煤气化实验。利用XRD、SEM和EDS等方法,考察了热处理后灰渣与煤气化所得炉渣的表面形态、内部微观结构、矿物组成等结构特性,并对管式电炉内进行灰渣热处理实验的可行性进行评估。结果表明,热处理温度和灰渣流动温度对灰渣的结构具有重大影响,热处理温度高于灰渣流动温度约10℃时,灰渣中含有大量矿物晶体且表面形态粗糙,内部微观结构凹凸不平,灰渣难于流动;热处理温度高于灰渣流动温度约100℃时,渣中大部分矿物晶体已变成无定形的玻璃体物质,灰渣表面及内部微观结构变得光滑均匀。采用管式电炉模拟气化炉内灰渣氛围,研究气化炉操作温度对灰渣结构的影响,具有一定的可行性。     

The determination of antimony and arsenic concentrations in fly ash by hydride generation inductively coupled plasma optical emission spectrometry

Hydride generation inductively coupled plasma optical emission spectrometry (HG-ICP-OES) was used in the determination of As and Sb concentrations in fly ash samples. The effect of sample pre-treatment reagents and measurement parameters used for hydride generation was evaluated. Due to memory effects observed, the appropriate read delay time was adjusted to 60 s resulting in RSDs 0.6% and 2.3% for As and Sb, respectively. The most suitable volumes of pre-reduction reagents for 10 mL of sample were 4 mL of KI/ascorbic acid (5%) and 6 mL of HCl (conc.). The determination of Sb was significantly interfered by HF, but the interference could be eliminated by adding 2 mL of saturated boric acid and heating the samples to 60 °C at least 45 min. The accuracy of the method was studied by analyses of SRM 1633b and two fly ash samples with the recovery test of added As and Sb. As high a recovery as 96% for SRM 1633b was reached for As using 193.696 nm with two-step ultrasound-assisted digestion. A recovery rate of 103% was obtained for Sb using 217.582 nm and the pre-reduction method with the addition of 2 mL of saturated boric acid and heating. The quantification limits for the determination of As and Sb in the fly ash samples using two-step ultrasound-assisted digestion followed with HG-ICP-OES were 0.89 and 1.37 mg kg⁻¹, respectively.     

A technique for sequential leaching of coal and fly ash resulting in good recovery of trace elements

Coal and fly ash contain many elements. These elements exist in different forms which may change throughout the coal combustion process. There are several processes, including X-ray techniques and leaching techniques by which studies have attempted to assess the form of a particular element in a sample. This work focuses on determining the leachability of selected elements sequentially leached in four extraction solutions: water, 1 M ammonium acetate, 3 M hydrochloric acid and 50% hydrofluoric acid. The emphasis is on evaluating the steps involved in the leaching process with the mass recovery for each element being the basis for evaluation. The total amount of each element that will leach out under the given extraction condition is presented as a fraction of the total present in the material. The materials evaluated were NIST coal and fly ash standards. The elements measured in this study include aluminum, barium, beryllium, calcium, chromium, cobalt, iron, magnesium, manganese, nickel, potassium, sodium, strontium, vanadium and zinc.     

Analysis of polycyclic aromatic compounds in the fly ash of an incineration plant for radioactive waste

Organic compounds adsorbed on fly ash from an incinerator for radioactive waste were investigated. Following Soxhlet extraction and concentration, analysis was performed by GC and GC/MS using high temperature silylated glass capillary columns coated with OV-1 and SE-54. Compound identification was based on retention data, relative detector responses, and mass spectra. Among other polycyclic aromatic compounds, series of gradually chlorinated PAHs containing four to seven aromatic rings were detected. For unequivocal identification, appropriate reference compounds were synthesized by chlorination of the corresponding parent PAHs.     

Application of sequential extraction and the ICP-AES method for study of the partitioning of metals in fly ashes

In this work, the original BCR extraction scheme was modified and applied to study the partitioning of metals in fly ashes. In the first step, the water-soluble fraction was investigated here. The next metal fractions were acid-soluble, reducible, and oxidisable. Two kinds of coal fly ash certified reference materials were analysed. Metal concentrations in the extracts were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). The efficiency of the extraction process for each step was examined. The partitioning of metals between the individual fractions was investigated and is discussed.     

The use of X-ray fluorescence (XRF) analysis in predicting the alkaline hydrothermal conversion of fly ash precipitates into zeolites

The use and application of synthetic zeolites for ion exchange, adsorption and catalysis has shown enormous potential in industry. In this study, X-ray fluorescence (XRF) analysis was used to determine Si and Al in fly ash (FA) precipitates. The Si and Al contents of the fly ash precipitates were used as indices for the alkaline hydrothermal conversion of the fly ash compounds into zeolites. Precipitates were collected by using a co-disposal reaction wherein fly ash is reacted with acid mine drainage (AMD). These co-disposal precipitates were then analysed by XRF spectrometry for quantitative determination of SiO₂ and Al₂O₃. The [SiO₂]/[Al₂O₃] ratio obtained in the precipitates range from 1.4 to 2.5. The [SiO₂]/[Al₂O₃] ratio was used to predict whether the fly ash precipitates could successfully be converted to faujasite zeolitic material by the synthetic method of [J. Haz. Mat. B 77 (2000) 123]. If the [SiO₂]/[Al₂O₃] ratio is higher than 1.5 in the fly ash precipitates, it favours the formation of faujasite. The zeolite synthesis included an alkaline hydrothermal conversion of the co-disposal precipitates, followed by aging for 8 h and crystallization at 100 °C. Different factors were investigated during the synthesis of zeolite to ascertain their influence on the end product. The factors included the amount of water in the starting material, composition of fly ash related starting material and the FA:NaOH ratio used for fusing the starting material. The mineralogical and physical analysis of the zeolitic material produced was performed by X-ray diffraction (XRD) and nitrogen Brunauer-Emmett-Teller (N₂ BET) surface analysis. Scanning electron microscopy (SEM) was used to determine the morphology of the zeolites, while inductively coupled mass spectrometry (ICP-MS), Fourier transformed infrared spectrometry (FT-IR) and Cation exchange capacity (CEC) [Report to Water Research Commission, RSA (2003) 15] techniques were used for chemical characterisation. The heavy and trace metal concentrations of the zeolite products were compared to that of the post-synthesis filtrate and of the precipitate materials used as Si and Al feed stock for zeolite formation, in order to determine the trends (increase or decrease) and ultimate fate of any toxic metals incorporated in the co-disposed precipitated residues.     

双介孔硅基材料负载Pd催化剂上甲苯氧化性能的研究

催化氧化技术是挥发性有机物(VOCs)减排与控制的主流技术之一,其关键之处在于高效催化材料的研究与开发,负载型贵金属催化材料由于其低温下优越的VOCs催化氧化性能,受到国内外研究者的广泛关注.对于负载型催化剂而言,载体的性质直接影响活性相的分散,反应物和生成物的扩散与吸脱附,是影响负载型催化剂性能的主要因素.近年来,多级孔结构硅基材料由于具有多级的孔道结构、高比表面积和大的孔体积,逐渐成为VOCs催化氧化材料的研究热点.本文采用溶胶凝胶法和浸渍法制备了系列双介孔结构硅基材料负载Pd催化剂(Pd/BMS-x),通过控制合成过程中氨水的用量以调节催化剂的介孔结构分布. X射线衍射(XRD)结果表明,所合成的Pd/BMS-x催化剂在~2.0°的衍射峰,类似于MCM-41的(100)晶面衍射峰,表明所有的样品均具有有序的介孔结构. N2吸脱附实验表明所有样品的比表面积均高于1000m2/g,孔径分布表明Pd/BMS-30样品为单一介孔结构,而Pd/BMS-5~Pd/BMS-20样品具有2.64 nm以及18–45 nm范围内的双介孔结构,且Pd/BMS-15样品介孔分布较为集中. Pd/BMS-x催化剂上甲苯催化氧化性能测试表明,双介孔结构的Pd/BMS-5~Pd/BMS-20催化剂上甲苯催化氧化活性远高于单一介孔结构的Pd/BMS-30催化剂,表明载体结构对催化剂性能有重要影响.其中, Pd/BMS-15催化剂性能最佳(T90为228°C)且具有较强的稳定性,250°C条件下,反应持续60h催化剂未见明显失活. SEM和TEM结果表明, Pd/BMS-15催化剂中Pd高度分散于载体上,平均粒径在~3 nm左右.而Pd/BMS-30催化剂中Pd颗粒间有明显的团聚,平均粒径在8~17 nm之间.分散度测试表明,单一介孔结构的Pd/BMS-30催化剂, Pd分散度仅为27%,而双介孔结构Pd/BMS-5–Pd/BMS-20催化剂介于39%到69%,其中Pd/BMS-15催化剂中Pd分散度高达69%.与常规单一介孔MCM-41和MCM-48负载Pd催化剂相比,在低空速(42000 h–1)条件下, Pd/BMS-15催化剂上甲苯催化氧化性能与Pd/MCM-41和Pd/MCM-48催化剂相当.高空速(70000h–1)条件下, Pd/BMS-15催化剂的活性远高于单一介孔的Pd/MCM-41和Pd/MCM-48催化剂. Pd/BMS-15催化剂独特的双介孔结构,有利于活性相Pd的分散、反应物的扩散和传输,特别是在高空速条件下,有利于反应物与活性相的接触,提高了材料的氧化反应性能.进一步考察了材料的水热稳定性,将11 vol%的水蒸气引入到反应体系中,测试结果表明水蒸气的加入导致Pd/MCM-41和Pd/MCM-48催化剂的甲苯催化氧化性能显著下降,反应500 min后甲苯转化率分别从100%下降到76%和81%,而对于Pd/BMS-15催化剂,水蒸气的引入并未导致其活性明显下降,从而表明Pd/BMS-15催化材料具有较高的水热稳定性.     

Study of catalytic hydrodeoxygenation performance for the Ni/KIT-6 catalysts

Ni/KIT-6 catalysts loaded with different amounts of metallic Ni were prepared by impregnation method. The prepared catalysts and their precursors were investigated through wide- and low-angle XRD, TEM, BET, H₂-TPR, and H₂-TPD analyzes. The catalytic hydrodeoxygenation performance of the catalysts was evaluated using ethyl acetate as a model bio oil compound. Results indicate that the catalytic hydrodeoxygenation performance of the prepared catalysts was directly related to hydrogen storage properties, hydrogen desorption properties, dispersion of the active component Ni, and so on. The ethyl acetate conversion and ethane selectivity of 25?wt% Ni/KIT-6 catalyst were 100 and 96.8%, respectively, at 300?°C, which shows the best performance. The hydrodeoxygenation activity of ethyl acetate was higher than that of methyl acetate and isopropyl acetate because of the effect of molecular polarity and size. And, this reaction is a structure sensitive reaction.     

Fire retarded polyurethane foam composites based on steel slag/ammonium polyphosphate system: A novel strategy for utilization of metallurgical solid waste

A series of FR-RPUF composites were prepared by a one-step water foaming process with ammonium polyphosphate (APP) and steel slag (SS) as flame retardants. Thermogravimetric analysis (TG), limiting oxygen index (LOI), UL-94 vertical combustion test, microscale combustion calorimetry (MCC), TG-Fourier transform infrared spectrometry (TG-FTIR), scanning electron microscopy (SEM), Raman spectra and FTIR were used to investigate the thermal stability, flame retardancy, combustion performance, gas phase products, and char residue morphology of FR-RPUF composites. TG test results showed that the initial decomposition temperature (T_-5wt%) and char residue rate at 700°C of RPUF/APP/SS composites were significantly enhanced by the addition of APP and SS, and the thermal stability of the composites was improved. Flame retardant test results confirmed the significantly increased LOI values of RPUF/APP/SS composites with V-0 rating. TG-FTIR also confirmed the obviously decreased release of toxic gases and flammable gases in the combustion of RPUF/APP/SS composites. SEM and Raman spectra of char residues for the composites suggested that APP/SS system improved the compactness and graphitization degree of char layer for RPUF/APP/SS composite. The above researches provide a new strategy for the utilization of SS in fire safety engineering.     

Enhanced electrochemical performance and mechanism study of AgLi1/3Sn2/3O2 for lithium storage

Herein, AgLi_1/3Sn_2/3O₂ with delafossite structure was prepared by treating the layered compound Li₂SnO₃ with molten AgNO₃ via ion exchange of Li⁺ for Ag⁺. The structure characterization and the electrochemical performance of AgLi_1/3Sn_2/3O₂ was thoroughly investigated. AgLi_1/3Sn_2/3O₂ is found to possess stacking lamellar morphology, which means small electrochemical impedance and so facilitates charge transfer kinetics during the cycling. Compared with Li₂SnO₃, due to the introducing of excellent electrical conductivity of silver, AgLi_1/3Sn_2/3O₂ exhibits improved electrochemical performance in terms of capacity, cycling stability and coulombic efficiency. The results show AgLi_1/3Sn_2/3O₂ presents favorable specific capacity of 339 mAh/g at current density of 200 mA/g after 50 cycles and initial coulombic efficiency of 96%. Ex situ XRD analysis revealed the reaction mechanism of AgLi_1/3Sn_2/3O₂ as an anode for lithium ion batteries.     

Adsorption and inhibition performance of the novel cationic Gemini surfactant as a safe corrosion inhibitor for carbon steel in hydrochloric acid

The new synthesized cationic Gemini surfactant (CGS) was tested as a corrosion inhibitor for carbon steel (CS) in 1.0?M hydrochloric acid using weight loss, electrochemical spectroscopy and potentiodynamic polarization. The inhibition efficiency is increased by increasing the CGS concentration and is almost constant within the temperature range studied. The inhibition was explained by adsorption of the CGS molecule on the CS surface. A mixed-type inhibitor is suggested for the inhibitory effects of CGS as revealed by the potentiodynamic polarization technique. The changes in impedance parameters suggested that the adsorption of the inhibitor on the CGS surface led to the formation of protective films. The adsorption of the CGS on the surface of CS obeys Langmuir adsorption isotherm. Thermodynamic and kinetic parameters were calculated and discussed.     

微波合成SrTiO~3的反应机理

研究了微波合成SrTiO~3的合成过程,XRD及电子探针的结果表明这一反应过程是由扩散控制,微波场的存在使扩散过程明显增强,存在有Sr和Ti元素的相互扩散,与常规合成有较大不同。从微波合成和常规合成反应产物的组成及显微结构等方面说明微波合成与常规合成具有不同的反应机理,微波合成在反应过程中没有出现其他的中间相,反应动力学计算表明反应过程的动力学符合Carter方程,反应的活化能为129kJ/mol,约为常规合成的1/2～1/3。     

The effects of chain length,embedded polar groups,pressure, and pore shape on structure and retention in reversed-phase liquid chromatography: Molecular-level insights from Monte Carlo simulations

Particle-based simulations using the configurational-bias and Gibbs ensemble Monte Carlo techniques are carried out to probe the effects of various chromatographic parameters on bonded-phase chain conformation, solvent penetration, and retention in reversed-phase liquid chromatography (RPLC). Specifically, we investigate the effects due to the length of the bonded-phase chains (C₁₈, C₈, and C₁), the inclusion of embedded polar groups (amide and ether) near the base of the bonded-phase chains, the column pressure (1, 400, and 1000 atm), and the pore shape (planar slit pore versus cylindrical pore with a 60 Å diameter). These simulations utilize a bonded-phase coverage of 2.9 μ$\mu$mol/m²and a mobile phase containing methanol at a molfraction of 33% (about 50% by volume). The simulations show that chain length, embedded polar groups, and pore shape significantly alter structural and retentive properties of the model RPLC system, whereas the column pressure has a relatively small effect. The simulation results are extensively compared to retention measurements. A molecular view of the RPLC retention mechanism emerges that is more complex than can be inferred from thermodynamic measurements.     

The monomolecular mechanism of the gas‐phase thermal decomposition of primary N‐nitramines

Using nonempirical methods and DFT‐methods the geometrical parameters formation enthalpies of molecules and radicals, energies dissociation of N? NO₂ bonds of primary and secondary N‐nitramines have been investigated. The basic tendencies in the changes of the geometrical and electronic structures, formation enthalpies, and dissociation energies have been analyzed in basic homologous series of nitramines. Various alternative mechanisms of the gas‐phase monomolecular thermal decomposition have been studied by of the example of N‐methylnitramine. The process of the aci‐form formation and its further multistage destruction is the most advantageous way of decomposition of the primary N‐nitramines. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Enhanced electrochemical performance and mechanism study of AgLi1/3Sn2/3O2 for lithium storage

AgLi_1/3Sn_2/3O₂ with delafossite structure is prepared by treating Li₂SnO₃ with molten AgNO₃ and it exhibits improved electrochemical performance compared to Li₂SnO₃.     

Electrochemical behavior and interfacial bonding mechanism of new synthesized carbocyclic inhibitor for exceptional corrosion resistance of steel alloy: DFTB,MD and experimental approaches

A new carbocyclic compound, namely 3-benzoyl-4-hydroxy-4-phenyl-2,6-(4-methylphenyl)cyclohexane-1,1-dicarbonitrile (MPC) was synthesized and characterized. Herein, MPC was used as green compounds and its anti-corrosion performance was evaluated on the basis of singular role of electron donor–acceptor of MPC molecule. For this purpose, a combination of experimental studies and electronic-/atomic-scale calculations were performed in a bid to understand the electrochemical behavior and interfacial mechanism of MPC molecule based on the correlation between electron charge transfer and adsorption mechanism. Theoretical perspectives are also used to validate the significant inhibition feature achieved by the experimental studies and propose a mechanism of adsorption by using density functional theory (DFT) and molecular dynamic (MD) simulations. According to DFT and MD perspectives, it is found that MPC presents strong interaction with metal surface due to its considerable ability to provide lone pair electrons for electrophilic attacks. This is demonstrated by the high adsorption energy (-5.83 eV) and the parallel configuration of MPC which reveal the formation of molecular self-assembly triggered by an organic-surface interaction. The reliable corrosion stability was provided for 72 h of immersion at an optimum concentration with a fairly high inhibition efficiency (85.81 %) due to the formation of organic inhibitive layer. The addition of MPC inhibitor worked as a sealing agent to reduce the corrosion rate, thus forming a dense and protective barrier on the metal surface. The corrosion resistance of mild steel sample was enhanced significantly due to a high adsorption ability arising from the electron-rich nature of molecule. The formation of organic layer on the metal surface was discussed in relation to the intermolecular interactions and microstructural observations by considering the charge transfer behavior responsible for exceptional corrosion protection of steel alloys. The computational simulations were consistent with the experimental results and confirm the importance of developing eco-friendly hybrid materials.     

The crosslinking mechanism in gamma irradiation of polyarylsulfone: evidence for Y-links

Measurements of molecular weights, soluble fractions and examination of NMR spectra of bisphenol-A polysulfone, after gamma irradiation in vacuum at 150°C were used to elucidate the mechanism of crosslinking. Excellent agreement was obtained between G(S) and G(X) determined from measurements above and below the gel dose when a Y-linking mechanism was assumed, whereas poor agreement was obtained when an H-link mechanism was assumed, which is the mechanism normally believed to be responsible for crosslinking. New resonances were observed in the ¹³C NMR spectra of the irradiated polymer which were consistent with the formation of Y-links involving phenylene units in the backbone chain. © 1998 John Wiley & Sons, Ltd.