Synthesis and Properties of a Novel Branched Polyether Surfactant

A novel branched polyether surfactant (TPE) was prepared by anion polymerization with different proportions of propylene oxide (PO) and ethylene oxide (EO) using 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane as a core. The structures and average molecular weight (M _n ) of the TPE were characterized by ¹H NMR and GPC. The cloud point was determined by turbidimetry in the presence of inorganic salts. Inorganic salts decreased the cloud point of TPE polyether in the following order: Na₂CO₃ > Na₂SO₄ > NaCl > CaCl₂ > MgCl₂. The effects of inorganic salts (NaCl, MgCl₂, CaCl₂, and NaSCN) and temperature on the surface activity of TPE in aqueous solution were investigated by surface tension measurements. The surface activity parameters and the thermodynamic parameters were calculated from surface tension data. Similar to the effect of increasing temperature, the salting-out inorganic salts such as NaCl, MgCl₂, and CaCl₂ favor the micellization and increase the maximum surface excess concentration, while the salting-in NaSCN has the opposite effect. The influence of NaCl on the morphology of micelles was investigated by TEM. The micellization is entropy-driven at low temperature and enthalpy-driven at higher temperature. The TPE polyether has large surface activity and can be used as a demulsifier to break up crude oil emulsions.     

Experimental investigation of the suppression effects of ammonium polyphosphate on explosion characteristics of unsaturated polyester resin dust

The suppression effects of Ammonium Polyphosphate (APP) with different mass fractions on the maximum explosion pressure (P_max), the explosibility index (K_st), the minimum ignition energy (MIE) and the minimum ignition temperature (MIT) of unsaturated polyester resin (UPR) dust were studied. Results indicated that the explosion severity and the ignition sensitivity of UPR dust decreased gradually when the mass fractions of APP increased. There existed a minimum inerting concentration (MIC), and the explosion of UPR dust could be suppressed completely by 60 wt% APP. Moreover, APP had a great inhibiting effect on the MIE of UPR dust cloud. The calculated MIE of UPR dust cloud increased from 10 mJ to 998 mJ when the mass fractions of APP increased to 30 wt%. Furthermore, the MIT of UPR dust cloud increased with the increase of the mass fractions of APP. When the mass fraction of APP increased to 80 wt%, the MIT increased by 290°C. The suppression mechanism of APP was studied according to thermogravimetry (TG) and differential scanning calorimetry (DSC) tests. Thermal analysis results showed that the addition of APP could increase the thermal stability of UPR. The suppression mechanism was reflected on the consumption of H and OH radicals.     

Dust cloud explosion characteristics and mechanisms in MgH2-based hydrogen storage materials

The mechanisms involved in premixed magnesium and hydrogen hybrid and synthetic MgH₂ dust cloud explosions were investigated. The results revealed that trace amounts of H₂ in Mg explosions can markedly increase explosion severity. Furthermore, H₂ addition can weaken the influence of oxygen deficiency on Mg explosion. Moreover, the explosion intensity of synthetic MgH₂ was far stronger than that of premixed Mg/H₂ mixture or Mg alone because the vacancy defects in Mg and H atoms can form after dehydrogenation of MgH₂, which caused that Mg and H₂ are prone to oxidation and nitrification in air atmosphere at a low temperature, thereby promoting the explosion. This demonstrates that the explosion risk of MgH₂ (even other H₂ storage materials) is related to its H₂ storage capacity and dehydrogenation temperature. Therefore, for H₂ storage materials, the better H₂ storage performances can exhibit higher explosion risks.     

Swelling behavior of sulfonated polyacrylamide nanocomposite hydrogels in electrolyte solutions: comparison of theoretical and experimental results

Nanocomposite hydrogels were prepared by cross-linking of aqueous solutions of sulfonated polyacrylamide/sodium montmorillonite with chromium triacetate as ionic cross-linker. The effect of montmorillonite content on equilibrium swelling in NaCl and CaCl₂ solutions, ultimate storage modulus and effective cross-link density was evaluated. The limiting storage modulus of the nanocomposite (NC) hydrogels dropped by increasing montmorillonite content up to 1,000?ppm, and then it increased by further montmorillonite loading. A mechanism is proposed for the formation of PAMPS/Na⁺-MMT/Cr³⁺ NC hydrogels. According to this mechanism, the drop in limiting storage modulus of the NC gels at low Na⁺-MMT concentration is due to ionic interactions between the negative layers of sodium montmorillonite and Cr³⁺, leading to decreased cross-link density. However, the increase of the limiting storage modulus of the NC gels at high clay concentration results from the strong interactions between the polyacrylamide chains and clay platelets. The equilibrium swelling ratio of the NC networks decreased with increase of montmorillonite content in both aqueous NaCl and CaCl₂ solutions. In addition, the experimental swelling data of these NC hydrogels were described by a modified Flory?CRehner theory. The modified model was sensitive to montmorillonite concentration and it described adequately the swelling data for NC gels in NaCl solutions. Nevertheless, theoretical predictions showed some deviations from experimental results for swelling of NC hydrogels in CaCl₂ solutions.     

Behavior of gas bubbles in aqueous electrolyte solutions

A system was investigated in which a swarm of air bubbles was dispersed in aqueous electrolyte solutions. the salts used were: NaCl, NaBr, NaI, Na₂SO₄, Na₃PO₄ LiCl, MgCl₂, MgSO₄, CaCl₂, AlCl₃ and Al₂(SO₄₃. The effects of the salts on the interfacial area of dispersion and on the oxygen transfer coefficient were investigated at various salt concentrations. The results showed a definite dependence of the surface area of dispersion on the valence of the ionic species and salt concentrations. A very satisfactory correlation was obtained for all the salts with the use of ionic strength as the correlating parameter. The mechanism of the coalescence-preventing action of the salts was discussed and explained on the basis of ion—water interactions. The oxygen mass transfer coefficient was found to be only slightly dependent on the presence of electrolytes in the range of concentrations used in this work. The importance and possible practical application of the results were briefly discussed.     

Effects of mineral addition on the growth morphology of and arachidonic acid production by Mortierella alpina 1S-4

The culture conditions for arachidonic acid (AA) production by Mortierella alpina 1S-4 were investigated by means of a morphological study with the aims of obtaining a high AA yield and scale-up. In a 50-L jar fermentor study, a medium containing 3.1% soy flour and 1.8% glucose with 0.3% KH₂PO₄, 0.1% Na₂SO₄, 0.05% CaCl₂·2H₂O and 0.05% MgCl₂·6H₂O was found to be optimum. The AA yield reached 9.8 g/L/7 d, and the major morphology was small pellets (1–2 mm). However, in the case of the only addition of KH₂PO₄, the major morphology was filaments. The apparent viscosity increased to 2240 cp, thereby requiring a high agitation speed to maintain adequate oxygen tension, which caused mycelial damage due to shear stress and therefore a decrease in the AA yield. When a medium with Na₂SO₄, CaCl₂, and MgCl₂ was used, the major morphology was large pellets (2–3 mm), and mass transfer limitation through the pellet wall caused a decrease in the AA yield. Based on these results, a scale-up study was carried out under the optimal conditions described above. An AA yield of 10.9 g/L/8 d was obtained in a 10-kL industrial fermentor, and the major morphology was small pellets.     

The studies on the stimuli‐response of poly (N,N‐dimethylamino ethyl methacrylate/acrylic acid‐co‐acrylamide) complex hydrogel under DC electric field

A polyelectrolyte complex hydrogel, poly (N,N‐dimethylaminoethyl methacrylate/acrylic acid‐co‐acrylamide) hydrogel designed as PDMEAA, was prepared by the free radical copolymerization in aqueous solutions. Without chemical crosslinker, PDMEAA hydrogel network was formed by electrostatic attraction of the proton‐transfer between acrylic acid and N,N‐dimethylamino ethyl methacrylate. Since the electrostatic attraction could be weakened by the application of electric field, PDMEAA hydrogel was decomposed under contacted electric field. Various factors such as gel composition, the species and concentration of electrolytes, voltage, and the experimental set‐ups, could effect the decomposing process of PDMEAA hydrogel. In CaCl₂ and MgCl₂ solutions, PDMEAA hydrogel had no change under electric field. And in high concentration of NaCl and Na₂SO₄ solutions, PDMEAA hydrogel has been eroded linearly with the increasing time applied electric field. In low concentration of NaCl and Na₂SO₄ solutions, however, a swelling process was found before the erosion. The stimuli‐responsive mechanism was investigated through scanning electron microscope (SEM) and gel permeation chromatography (GPC). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Isolation,Amino Acid composition and molecular weight distribution ofEucalyptus kirtoniana seed proteins

Proteins were extracted from the deoiled seeds ofEucalyptus kirtoniana in aqueous solutions of various pHs or by different concentrations of NaCl, Na₂SO₃, CaCl₂ and MgCl₂ at pH 8.0. Amino acid analysis of the isolated protein identified 16 amino acids, nine of which were essential. Gel permeation chromatography on Sephadex G-200 revealed the presence of four components in the protein fraction, and their molecular weights were determined by two comparable standard methods. SDS-PAG electrophoresis demonstrated that each protein isolate from different salt solutions was composed of six fractions whose molecular weights were estimated to be 131,800; 108,300; 93,300; 51,300; 38,000 and 25,700 daltons.     

基于贝叶斯网络的粉尘爆炸多米诺效应分析

粉尘爆炸机理的复杂性及引起粉尘爆炸因素的多样性使得粉尘爆炸成为学者们研究的热点课题,目前研究成果集中在不同种类粉尘的爆炸特性、粉尘爆炸机理、预防和减轻粉尘爆炸的安全措施及粉尘爆炸定量风险分析等方面,但在建立粉尘爆炸相关模型及风险评价方面的研究较少。本文在剖析粉尘爆炸机理的基础上结合多米诺效应原理建立了粉尘爆炸多米诺效应计算模型,该模型在计算出初始粉尘爆炸事故的条件概率后,利用贝叶斯网络灵活的特性和自动推理引擎,可以计算出潜在多米诺效应传播的途径。通过实例应用该模型的计算结果,可以得出发生粉尘爆炸多米诺效应的概率变化情况及粉尘爆炸事故最可能发生的传播途径,为粉尘爆炸事故的预防控制及风险评价提供了方向。     

Thermal Behavior of Nitrocellulose with Inorganic Salts and their Mechanistic Action

In this study, we investigated the effects of inorganic salts on the stability of NC and its reaction mechanism. Under isothermal conditions at 120 °C in an O₂ atmosphere, the induction time period for NC heat release was prolonged in the presence of Li₂CO₃, Na₂CO₃, CaCO₃, Mg(OH)₂, Ca(OH)₂, and MgO, all of which produce alkaline saturated solutions with a pH value of 10–12. In addition, the induction time period depended on this pH value. This suggests that these salts stabilized NC by neutralizing acids that would otherwise accelerate the hydrolysis of the O‐NO₂ bond. However, Sr(OH)₂ ⋅ 8H₂O and K₂CO₃, which produce strongly alkaline saturated solutions with pH>13, decreased the induction time period. It is possible that these strong bases caused alkaline decomposition of NC. In addition, for Sr(OH)₂ ⋅ 8H₂O, the released water of crystallization appeared to be related to NC destabilization. SrCO₃, NaHCO₃, K₂SO₄, CaSO₄, ZnSO₄, NaCl, CaCl₂, AgCl, and NaNO₂, which produce near‐neutral saturated solutions, slightly decreased the NC induction time period. The NC induction time period with these salts depended upon the solubility of the added salt. This may indicate that in the presence of these inorganic salts, the boiling point of water is increased, which reduces the vaporization of water from NC and thus accelerates the hydrolysis of NC.     

Transfer of Monovalent and Divalent Cations in Salt Solutions by Electrodialysis

Abstract

The selectivity mechanism of transport of Na⁺, Ca²⁺ and Mg²⁺ through commercial monovalent‐cation permselective membranes is investigated in batch electrodialysis experiments with synthetic salt solutions containing monovalent and divalent cations. The role of hydration energy, steric effect, kinetic effect as well as effects of permselectivity of cation exchange membrane has been elucidated with electrodialysis of single solutions (NaCl, CaCl₂, MgCl₂). The mechanism of interferences is investigated in (Na⁺/Ca²⁺, Na⁺/Mg²⁺, Ca²⁺/Mg²⁺ and Na⁺/Ca²⁺/Mg²⁺) mixtures.     

Thermal energy storage in inorganic salts

The work involved studying the potential of Na₂SO₄, NaCl, KCl, CaCl₂ and some eutectic mixtures of inorganic salt for storing thermal energy. Heat storage materials have wide application in devices such as “off-peak” space heating furnaces. Data reveal Na₂SO₄ to be a better heat storage material than other salts as well as conventional heat storage materials because of its dimorphic nature and high heat of transition. It is estimated that less than 0.29 m³ of Na₂SO₄ would be required for heating a normal sized house on the Canadian Prairies.     

Atmospheric Aging of Asian Dust Particles During Long Range Transport

Variations of mixing state and chemical constituents of Asian dust (AD) particles having different transport pathways were investigated by measuring hygroscopicity and volatility of size-selected (1 μm) dust particles, and their morphology and elemental composition in Gwangju, Korea. Also, hygroscopicity and volatility of possible candidate chemical species that can be included in the dust particles was measured in a laboratory for comparison with field data. A significant amount of dust particles were found to be aged by internally mixing with hygroscopic and volatile species in different ways, depending on their transport pathway. Formation of hygroscopic CaCl₂ and/or cloud processing of dust particles with sea-salt species were proposed as being central to the formation of hygroscopic species in the “less polluted AD” (in which the air mass arrived at sampling site without passing over significant industrial areas), and the existence of hygroscopic species in the “highly polluted AD” (in which the air mass passed over major industrial areas) was explained by the interaction of dust particles with anthropogenic pollutants (i.e., Ca(NO₃)₂ formation by heterogeneous reaction of HNO₃ with dust particles and condensation of hygroscopic H₂SO₄ or (NH₄)₂SO₄ onto the dust particles). Volatile carbonaceous species, which would exist on the surface of the dust particles, were also observed and their fraction significantly increased in the highly polluted AD due to a higher possibility to encounter air masses containing a significant amount of carbonaceous species. Morphological and elemental data identified three types of aged dust particles (reacted dust, cloud-processed dust, and aggregated dust). The production of various aged dust particles depending on their transport pathways has important implications on their different effects on cloud formation, radiation balance, and human health from original dust particles.

Copyright 2012 American Association for Aerosol Research     

Modelling the effect of particle size on dust explosions

The recent concept of inherent safety uses the properties of a material or process to eliminate or reduce the risk thus removing or minimizing the hazard at the source as opposed to accept the hazard and looking to mitigate the effects. In this framework the control of particle size in dust explosion prevention and mitigation is recognized as a major inherent safety methodology. Indeed, the increase of particle size may allow significant reduction of particle reaction rate eventually reducing the risk.In this paper a novel model is developed to quantify the effect of particle size on dust reactivity in an explosion phenomenon. The model takes into account all of the steps involved in a dust explosion: internal and external heating, devolatilization reaction and volatiles combustion. Varying the dust size can establish different regimes depending on the values of the characteristic time of each step and of several dimensionless numbers (Damköhler number, Da; Biot number, Bi; thermal Thiele number, Th). Results from the model are reported in terms of the deflagration index (K_St) as a function of dust diameter in all regimes and at varying Da, Th and Bi. Comparison with experimental data from polyethylene explosion tests shows promising results. Finally, the results of the model are presented in the form of a dust explosion regime diagram, which is helpful to make a draft evaluation of the role of dust size on explosion behavior and severity.     

Influence of nanocrystallization on passive behavior of Ni-based superalloy in acidic solutions

The electrochemical corrosion behaviors of Ni-based superalloy nanocrystalline coating (NC) fabricated by a magnetron sputtering technique have been investigated in comparison with cast alloy in 0.25 M Na₂SO₄ + 0.05 M H₂SO₄ and 0.5 M NaCl + 0.05 M H₂SO₄ solution, respectively. Compared with cast alloy, the NC coating had a little higher passive current density in Na₂SO₄ acidic solution, while it had superior resistance to pitting corrosion in NaCl acidic solution. The semiconductive type of passive film of the NC coating was p-type in both acidic solutions, while, that of cast alloy changed from p-type in Na₂SO₄ acidic solution to n-type in NaCl acidic solution. XPS results indicated that Cr₂O₃ was the main component for the passive films of the NC coating as well as those of the cast alloy. No chloride ion was found in the passive film of NC coating while it was in the passive film of cast alloy. The chloride ions adsorbing on the surface of cast alloy incorporated into the passive film, which induced the formation of n-type oxide film. The nanocrystallization of Ni-base superalloy obviously weakened the adsorption of chloride ions on surface, which decreased the susceptibility of pitting corrosion in acidic solution.     

Hexamethylene diisocyanate crosslinking 2‐hydroxypropyltrimethyl ammonium chloride chitosan/poly(acrylonitrile) composite nanofiltration membrane

The effects of membrane preparation conditions on membrane properties were studied in detail. The results suggested that composite nanofiltration (NF) membrane from 2.0 wt % 2‐hydroxypropyltrimethyl ammonium chloride chitosan (HACC) vaporized for 2.5 h at 50°C, and then crosslinked for 9 h at 50°C with hexamethylene diisocyanate (HDI)/ethanol (0.45/50 wt/wt) were found to have optimal performance. The resultant membrane was called HACC/PAN [poly(acrylonitrile)] NF membrane. The characteristics of this membrane such as pure water permeability, molecular weight cut‐off, rejection of salts, and swelling were investigated. And its cut‐off molecular weight (MWCO) was ～520 Da. At 25°C and 1.0 MPa, the permeability of water was 17.24 L/h m² MPa. Swelling in water decreased and rejection of salts increased with increasing HDI concentration, indicating pore contraction and increase in hydrophobicity as well as pore tortuosity due to crosslinking. The order of rejection to different salt solutes followed the decreasing of CaCl₂, MgCl₂, NaCl, KCl, and Na₂SO₄, suggesting that this membrane was positively charged. The rejections to MgCl₂ and CaCl₂ were more than 0.90; therefore, this membrane can be used for hardness removal in water treatment process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007.     

Minimum ignition temperature of polyethylene dust: a theoretical model

Dust explosion hazard exists in plants and facilities handling combustible dusts. The minimum ignition temperature of dust clouds is an important parameter requiring special attention to designing the explosion preventive measures. This paper presents a model developed for determining the minimum ignition temperature for an organic dust cloud, polyethylene, simulating the conditions in the Godbert-Greenwald furnace. The model correlates the particle size, as well as the dust concentration with the minimum ignition temperature. It is based on the two-stage oxidation mechanism involving devolatilization/decomposition of the solid particle and homogeneous oxidation of volatile combustible products. In the case of polyethylene, the main combustible gas responsible for ignition and flame propagation has been confirmed to be butylene. The results of the computations were compared with the experimental values and those predicted by Mitsui and Tanaka. The predicted values by the model developed are in close agreement with the experimental data which confirm the proposed ignition mechanism. The model can be used for the prediction of minimum ignition temperature of organic dusts having an autoignition mechanism similar to polyethylene dust. © 1997 John Wiley & Sons, Ltd.     

The stability of bound chlorides in cement paste with sulfate attack

This paper presents an experimental investigation on the stability of bound chlorides in chloride-contaminated cement pastes with and without FA/GGBS when subjected to Na₂SO₄ and MgSO₄ attack. It is shown that bound chlorides were released in the chloride-contaminated pastes when exposed to Na₂SO₄ or MgSO₄ solution. This is mainly attributed to the decomposition of Friedel's salt (FS), where Cl⁻ bound in FS is replaced by SO₄²⁻. However there were fewer released chlorides found in the pastes exposed to MgSO₄ solution than in those exposed to Na₂SO₄ solution. This is partly due to the low pH in the pore solution and partly due to the blocking effect of brucite on ionic transport caused by MgSO₄. The inclusion of FA/GGBS in concrete can increase the decomposition of FS and thus the release of bound chlorides. However, it also resists the penetration of Na₂SO₄ and thus reduces the attack of Na₂SO₄.     

Coal dust/air explosions in a large-scale tube

Coal dust/air mixture explosions under weak ignition conditions have been studied in a horizontal experimental tube of diameter 199 mm and length 29.6 m. The experimental tube is closed at one end and open at the downstream end. An array of 40 equally spaced dust dispersion units was used to disperse coal dust particles into the experimental tube. The coal dust/air mixture was ignited by an electric spark. A constant-temperature hot-wire anemometer was used to measure the gas velocity during the dispersion process. Kistler piezoelectric pressure sensors were used to measure the propagation of the pressure wave during the explosion process. The maximum overpressure of the coal dust explosion under the weak ignition conditions in the tube was 70 kPa and the propagation velocity of the pressure wave along the tube was approximately 370 m/s. The minimum concentration for obtaining a coal dust explosion that propagated along the tube was 120 g/m³. The suppressing effects on the coal dust explosion of two different kinds of suppressing agents have been studied.     

The effects of coal dust concentrations and particle sizes on the minimum auto‐ignition temperature of a coal dust cloud

Flash fires and explosions in areas containing an enriched combustible dust atmosphere are a major safety concern in industrial processing. An experimental study was conducted to analyse the effects of atmospheric coal dust particle sizes and concentrations on the minimum auto‐ignition temperature (MAIT) of a dust cloud. Two different coal samples from Australian coal mines were used. The coal dust particles were prepared and sized in 3 ranges, of below 74 μm, 74 to 125 μm and 125 to 212 μm, by using a series of sieves and a sieve shaker. A humidifier was used to increase the moisture content of the particles to the required level. All the experiments were conducted in accordance with the ASTM E1491‐06 method in a calibrated Goldbert‐Greenwald furnace. The results from this study indicate that coal dust properties, such as the chemical nature (H/C), concentration, particle size (D₅₀), and moisture content, impact on the MAIT. For coal dust concentrations less than 1000 g.m^?3, the MAIT decreases with increasing coal dust concentrations. On the other hand, for low concentrations of 100 to 15 g.m^?3, the MAIT becomes more reliable for particle size D₅₀ rather than for volatile matters.