氯盐溶液中甲烷水合物高压分解条件及影响因素

向水合物储层注入盐类溶液是水合物常规开采技术之一,所以必须掌握储层压力条件下盐类溶液中水合物分解条件及其影响因素.本文研究了NaCl、MgCl2、CaCl2氯盐溶液中甲烷水合物分解条件,结果表明NaCl(2.0、1.0、0.5 mol·L-1)、MgCl2 (1.0、0.5 mol·L-1)和CaCl2 (1.0、0.5 mol·L-1)溶液中甲烷水合物的分解温度比纯水中分别降低了(4.8、2.4、1.0 K (NaCl))、(5.3、1.5 K (MgCl2))和(4.3、1.8 K (CaCl2)).以van der Waals 和Platteeuw 热力学模型为基础,结合电解质溶液中水的活度方程(Pitzer-Mayorga 方程),给出了氯盐溶液中水合物分解条件热力学模型,进而比较了模型计算值与实验值,结果显示两者非常吻合.分析表明,氯盐溶液中离子静电作用产生的水分子溶剂化效应和盐析效应降低了水的活度而导致水合物分解温度降低.     

疏水修饰聚丙烯酸共聚物在水溶液中的缔合作用

丙烯酸类共聚物具有良好的增稠,分散,成膜和絮凝等性能,因而在涂料,皮革,油漆,颜料及油田开发等领域具有广泛的用途^[1],但当体系中可溶性盐类含量高时,该类水溶性大分子的使用效果不降,而疏水修饰共聚物可克服原聚合物对高价金属离子敏感的缺陷^[2],疏水修饰共聚物在水溶液中可缔合成胶束状团簇（MLCs),造成大分子的流体动力学尺寸增大,从而使溶液粘度增大,MLCs的疏水微区可增溶油类物质,因此疏水修饰大分子可作为含高价离子浓度体系的流度控制剂^[3],本文利用荧光探针技术^[4,6]探讨了丙烯酸丁酯－丙烯酸－甲基丙烯酸共聚物在纯水和盐水溶液中的缔合作用。     

Viscosity of aqueous calcium chloride solutions at high temperatures and high pressures

Viscosity of six (0.10, 0.33, 0.65, 0.97, 1.40, and 2.00) mol kg⁻¹ binary aqueous CaCl₂ solutions has been measured with a capillary-flow technique. Measurements were made at pressures up to 60 MPa. The range of temperature was from 293 to 575 K. The total uncertainty of viscosity, pressure, temperature, and composition measurements was estimated to be less than 1.6%, 0.05%, 15 mK, and 0.014%, respectively. The effect of temperature, pressure, and concentration on viscosity of binary aqueous CaCl₂ solutions was studied. The measured values of viscosity of CaCl₂(aq) were compared with data, predictions, and correlations reported in the literature. The temperature and pressure coefficients of viscosity of CaCl₂(aq) were studied as a function of concentration and temperature. The viscosity data have been interpreted in terms of the extended Jones–Dole equation for the relative viscosity (η/η₀) to accurate calculate the values of viscosity A- and B-coefficients as a function of temperature. The derived values of the viscosity B-coefficients were compared with the values calculated from the ionic B-coefficient data. The physical meaning parameters V and E in the absolute rate theory of viscosity and hydrodynamic molar volume (effective rigid molar volume of salt) V_k were calculated using present experimental viscosity data. TTG model has been used to compare predicted values of the viscosity of CaCl₂(aq) solutions with experimental values at high pressures.     

黄原胶和瓜尔胶混合溶液及其硼砂交联体系的流变性能

本文研究了黄原胶(XG)和瓜尔胶(GG)的混合溶液及其硼砂(B)交联体系的流变性,考察了XG/GG间的“协同增效作用”以及溶液组成、pH和电解质(NaCl和CaCl 2)对其流变性的影响。结果表明,所有溶液体系均为假塑型流体,其流变曲线可用Herschel-Bulkley和Casson模型描述。XG和GG复配具有明显的“协同增粘效应”,在XG占两聚合物的质量分数w(XG)为20%和90%时协同增粘效应最强,其“协同增粘率”(R m)分别约为42%和34%。硼砂(B)可交联XG/GG混合溶液,其交联增粘效果随w(XG)的减小和硼砂质量浓度ρ(B)的增大而增大;在w(XG)=50%和ρ(B)=1.00 g/L时,“交联增粘率”可达85%。在所研究的pH值范围(6.2~10.0)内,XG/GG混合溶液的流变性基本无变化,而XG/GG/B交联体系(w(XG)=50%和ρ(B)=0.75~1.00 g/L)的表观粘度随pH值增大先升高后降低,pH=9.0时出现最大值,交联增粘率达107%。电解质可使XG/GG/B交联溶液(w(XG)=10%和ρ(B)=0.50 g/L)体系的粘度大幅下降,且CaCl 2的影响明显高于NaCl,表明交联结构的耐盐能力较差。这些结果加深了对XG/GG混合溶液流变性的认识,可为其实际应用(如在强化采油中的应用)提供依据。     

Influence of operating conditions on the retention of phosphate in water by nanofiltration

The objective of this study was to investigate the retention of phosphate anions, H₂PO₄⁻ and HPO₄²⁻, by nanofiltration. The first part of this study deals with the characterisation of the NF200 membrane used in permeation experiments with aqueous solutions of neutral organic and charged inorganic solutes. In the second part the effects of feed pressure, ionic strength, concentration and pH on the retention of phosphate anions were investigated. Results show that the membrane is negatively charged, its pore radius is around 0.5 nm and the retention order for the salts tested was R(Na₂SO₄) > R(NaCl) > R(CaCl₂). The retentions of phosphate anions are in the order of 85% for H₂PO₄⁻ and 96% for HPO₄²⁻. They are relatively high when compared to retentions of other anions with the same charge. The retentions of phosphate anions, particularly the monovalent species, depend on the chemical parameters (feed concentration, ionic strength, and pH) and applied pressure. The experimental data were analysed using the Speigler–Kedem model and the transport parameters, i.e., the reflection coefficient (σ) and solute permeability (P_s) have been determined.     

Molecular Dynamics Simulation for the Impact of External Electric Fields on CaCl2 Aqueous Solution

Non-equilibrium molecular dynamics(MD) simulations were performed according to the electronic anti-fouling technology, and some structural parameters and dynamic parameters of CaCl₂ aqueous solution were taken as indicators to compare the different effect on the anti-fouling performance by applying different electric fields. The results show that electric fields can effectively decrease the viscosity of CaCl₂ aqueous solution and enhance the ionic activity by enlarging the self-diffusion coefficient. In addition, with the same electric field strength, the electrostatic field is more effective at decreasing the viscosity of CaCl₂ aqueous solution and increasing the self-diffusion coefficient of water molecules, while the alternating electric field is more effective at increasing the self-diffusion coefficient of Ca²⁺. Furthermore, an alternating electric field with different frequencies was applied; the results show that an 800 kHz frequency is most effective to decrease the viscosity, and a 700 kHz frequency is most effective to enhance the self-diffusion coefficient of water molecule. Otherwise, 400 kHz is most effective to enhance the self-diffusion coefficient of Ca²⁺. Additionally, by studying the change of structure parameters, it was concluded that an external electric field can enhance the hydration between Ca²⁺ and coordinated water molecules, and the alterna- ting electric field is more effective in this respect.     

Calcium Ion Coordinated Polyamide Nanofiltration Membrane for Ultrahigh Perm-selectivity Desalination

Improving the permeate flux but retaining the rejection of thin-film composite(TFC) polyamide nanofiltration(NF) membrane is a high requirement for desalination. In this work, a calcium ion(Ca²⁺) coordinated polyamide(PA) NF membrane was prepared by directly adding CaCl₂ to the piperazine(PIP) aqueous solution during the interfacial polymerization process. Due to the coordination interaction between Ca²⁺ and the amide bond in PA active layer, the number of hydrogen bonds in the PA active layer was reduced, causing in turn the decrease of physical cross-linking degree. As a consequence, the pore of the PA active layer was enlarged, prominently enhancing the water permeance of NF membrane. With the increase of CaCl₂ concentration, the pure water flux of TFC NF increased significantly while the rejection of Na₂SO₄ decreased sightly. Compared with TFC NF membrane prepared without CaCl₂, the permeate flux of the Ca²⁺ coordinated polyamide NF membrane prepared under optimal conditions was increased by 3-4 folds with Na₂SO₄ rejection of 95.26%. Meanwhile, such a Ca²⁺ coordinated PA NF membrane showed a better SO₄^2-/Cl^- selectivity.     

电势诱导的N-异丁酰基-L-半胱氨酸分子在金(111)表面的相转变

Functional solid substrates modified by self-assembled monolayers (SAMs) have potential applications in biosensors, chromatography, and biocompatible materials. The potential-induced phase transition of N-isobutyryl-L-cysteine (L-NIBC) SAMs on Au (111) surfaces was investigated by in-situ electrochemical scanning tunneling microscopy (EC-STM) in 0.1 mol·L^-1 H₂SO₄ solution. The NIBC SAMs with two distinct structures (α phase and β phase) can be prepared by immersing the Au (111) substrate in pure NIBC aqueous solution and NIBC solution controlled by phosphate buffer at pH 7, respectively. The as-prepared α phase and β phase of NIBC SAMs show various structural changes under the control of electrochemical potentials of the Au (111) in H₂SO₄ solution. The α phase NIBC SAMs exhibit structural changes from ordered to disordered structures with potential changes from 0.7 V (vs saturated calomel electrode, SCE) to 0.2 V. However, the β phase NIBC SAMs undergo structural changes from disordered structures (E < 0.3 V) to γ phase (0.4 V < E < 0.5 V) and finally to the β phase (0.5 V < E < 0.7 V). EC-STM images also indicate that the phase transition from the β phase NIBC SAMs to the α phase occurs at positive potential. Combined with density functional theory (DFT) calculations, the phase transition from the β phase to the α phase is explained by the potential-induced break of bonding interactions between ——COO^- and the negatively charged gold surfaces.     

Modification of radiation resistance of Bacillus spores by water

Spores of Bacillus subtilis, containing plasmid (B. subtilis BD 366(pUB110, Trp C2 thr 5)), were prepared free of additives and the effect of water on their radiation sensitivity under aerobic condition was investigated. The moisture content of spores was controlled by (i) drying over CaCl₂ (Aw = 0.0), (ii) equilibrating with the vapor of saturated aqueous NaCl solution (Aw = 0.7), or (iii) suspending in water (Aw = 1.0). The resistance of spores to radiation increased with increasing moisture content. The analysis of spore DNA by agarose gel electrophoresis showed that DNA damage (strand breaks) decreased with increasing water activity of the spores, a finding concomitant with the observed survival rates.     

Enthalpies of solution of SrCl2 and BaCl2 in aqueous mixtures of methanol and ethanol at 298.15 K

Enthalpies of solution of alkaline earth metal chlorides have been determined in water and aqueous mixtures of methanol and ethanol, and the enthalpies of transfer obtained. Plots of standard enthalpy of solution ΔH_m^XXX vs. binary solvent composition are discussed and compared with the corresponding curve for water-methanol solutions of CaCl₂.     

Preparation and characterization of N,O-carboxymethyl chitosan (NOCC)/polysulfone (PS) composite nanofiltration membranes

N,O-carboxymethyl chitosan (NOCC) composite nanofiltration membranes having a polysulfone (PS) UF membrane as the substrate were prepared using a method of coating and cross-linking, in which a glutaraldehyde (GA) aqueous solution was used as the cross-linking agent. Attenuated total reflection infrared spectroscopy (ATR-IR) was employed to characterize the resulting membrane. The effects of the composition of the casting solution of the active layer, the concentration of the cross-linking agent, and the membrane preparation techniques on the performance of the composite membrane were investigated. At 13–15 °C and 0.40 MPa the rejections of the resulting membrane to Na₂SO₄ and NaCl solutions (1000 mg L⁻¹) were 92.7 and 30.2%, respectively, and the permeate fluxes were 3.0 and 5.1 kg m⁻² h⁻¹, respectively. The rejection of this kind of membrane to the electrolyte solutions decreased in the order of Na₂SO₄, NaCl, MgSO₄, and MgCl₂. This suggests that the membrane active layer acquires a negative surface charge distribution by the adsorption of anions from the electrolyte solution and this charge distribution mainly determines the membrane performance.     

Nature of surface oxygen intermediates on TiO2 during photocatalytic splitting of water

The surface oxygenated intermediates present on TiO₂ during photocatalytic water splitting have been identified and their accumulation on the titania surface is responsible for the deactivation of H₂ evolution rate during photocatalysis.     

Micellization and adsorption of a zwitterionic surfactant: N-dodecyl betaine-effect of salt

Time-resolved fluorescence quenching, self-diffusion measurements and calorimetric investigations have been used in order to investigate the effect of salt on aggregation in aqueous solutions and the adsorption onto silica gel of the zwitterionic surfactant N-dodecyl betaine (NDB).

The micelle aggregation number of NDB stays constant when the NDB or salt concentration increases but decreases with an increase of temperature. Evidence is presented for the binding of cations and anions to micellar aggregates. The degree of binding has been obtained for Na⁺, Ca²⁺ and Cl⁻ ions; it is always larger for the anion.

Enthalpies of micellization were obtained directly from calorimetric curves of NDB in dilution experiments. The observed decrease of the endothermic enthalpies of micellization with increasing temperature or salinity is attributed to a structural change in the water molecules around the alkyl chain of the free monomers.

The adsorption isotherms of NDB onto silica gel depend very little on temperature, and a plateau is reached near the CMC. At saturation, the adsorbed amount of NDB depends on the salt and follows the sequence NDB < (NDB + NaCl) < (NDB + CaCl₂).

The exothermic differential molar enthalpies of adsorption demonstrate the same behaviour as the enthalpies of micellization with varying temperature or salinity. Adsorption onto silica gel depends on the NDB concentration, the salt concentration and temperature.     

Characterization and decomposition mechanism of an unusual nickel, thiocyanate and 4-methylpyridine polymeric complex

The synthesis, characterization, and thermal decomposition of the [Ni(SCN)₂(H⁺SCN)₂(4-mepy)₂] compound with an octahedral structure in polymeric chain were reported, in which SCN groups form bridges among Ni(II) ions. The compound decomposes in water resulting in a pH<4 solution. The FT-IR spectrum presented doublet bands at 2117; 2128 cm⁻¹, 788; 773 cm⁻¹ assigned to ν(C---N) and ν(C---S) stretching modes, respectively, and δ(SCN) deformation modes at 468; 476 cm⁻¹. The Raman spectrum of the compound presented the ν(C---N) stretching as a strong doublet at 2122; 2128 cm⁻¹, ν(C---S) at 783; 770 cm⁻¹, and δ(SCN) at 468; 477 cm⁻¹. No significant changes were observed in the 4-mepy ligand bands compared with the vibrational frequencies of the pure compound or the compound in aqueous solution 0.2 mol l⁻¹. The crystal UV–vis reflectance spectrum presented two bands centered in 626 and 424 nm tentatively assigned to the d→d type transitions, ³A_2g→³T_1g and ³A_2g→³T_1g, for a symmetry close to O_h. The TG curve showed a mass loss between 120 and 200 °C assigned to the loss of the two 4-mepy molecules; from 200 to 265 °C, the loss of the two H⁺SCN groups; and from 265 to 450 °C, the loss of the two SCN groups that formed the bridges among the nickel atoms. Based on these mass loss data, a mechanism of thermal decomposition for the compound was proposed.     

辛烷基酚聚氧乙烯醚反相微乳体系的相行为及纳米复合碳酸盐的制备

绘制了一系列辛烷基酚聚氧乙烯醚(OP-10)+正辛醇+环己烷+水(或CaCl₂水溶液)拟三元体系相图,分别研究了助表面活性剂正辛醇的添加比例和CaCl₂水溶液的浓度对微乳区域的影响,发现在OP-10+正辛醇+环己烷+水拟三元体系相图中,随着正辛醇/OP-10的质量比逐渐增大,微乳区的面积逐渐增大,当正辛醇/OP-10质量比为1:2.5时微乳区的面积最大,之后微乳区面积随着其质量比的增大而减小,表明适量地加入助表面活性剂正辛醇有利于微乳区的形成;但过多地增加正辛醇的量反而不利于微乳相的形成。 确定正辛醇/OP-10的质量比为1:2.5,改变CaCl₂的浓度,发现OP-10+正辛醇+环己烷+CaCl₂水溶液拟三元体系相图中,CaCl₂浓度为0.1 mol/L时微乳区面积最大。分别配制总浓度为0.1 mol/L的5种不同摩尔比的Ca²⁺/Ba²⁺微乳液,并与等摩尔的碳酸钠水溶液反应制备共沉淀碳酸盐,使用扫描电子显微镜(SEM)对所制备样品进行表征分析,发现当微乳液为钙离子盐时,主要形成大的立方形颗粒;掺入钡离子,Ca²⁺和Ba²⁺摩尔比为3:1、1:1和1:3时,形成的沉淀分别为四棱锥形、球形和玉米棒形;当微乳液为钡离子盐时,沉淀主要为不规则多面体。     

Calcium as a factor influencing the response of Serratia marcescens strain SMG40 to growth surfaces

Serratia marcescens, like several other bacterial species, is able to adhere to and swarm on growth surfaces, and this property is correlated with changes in the structures and functions of cells which pass from broth to solid media. In the case of the pigmented form of S. marcescens strain SMG40, the response to the contact with agar was influenced by the presence of Ca²⁺ ions as follows. (1) In the swimming phase, i.e. in soft 0.35% agar media, expansion was not modified upon the addition of 5–35 mM Ca²⁺ ions. (2) On growth surfaces inducing swarming, i.e. on media containing 0.75% agar (low agar), Ca²⁺ ions used at low concentrations (e.g. 0.5mM) enhanced both growth and expansion. (3) At higher concentrations (from 3 mM). the Ca²⁺ ions inhibited expansion but not growth. Correlatively, the cell density per unit of the surface occupied by bacteria inhibited from swarming was increased: expansion rates of swarms at successive periods were lower and showed less fluctuation than normal. In a non-pigmented but still good swarmer mutant, found to be more sensitive to calcium, expansion was reduced to 50% with at most 0.5 mM Ca²⁺ ions. One-step revenants recovered pigmentation and the initial response to Ca²⁺ ions described in points (2) and (3) above. The inhibitory activity of CaCl₂ was partly antagonized by NaCl. Other properties implied in the interactions of Serratia cells with agar, i.e. pigmentation, adherence to solid surfaces and the production of an extracellular surfactant were not inhibited by Ca²⁺ ions.     

The mechanism of lipopolysaccharide infiltration through HUVEC membrane surface in direct endotoxin injury

In this study, the HUVEC's cellular biomechanical properties of HUVEC (elastic modulus K₁, K₂ and viscoefficient μ) were determined with micropipette aspiration system and analyzed after being directly damaged with lipopolysaccharide (LPS). The phospholipid compositions of HUVEC membrane were analyzed with high-performance capillary electrophoresis and PLA₂ activity was determined to research the modification and metabolism of HUVEC membrane phospholipid. Infiltration of LPS on HUVEC membrane was studied by observation with confocal microscopy and fluorescent microscopy. Results showed that LPS direct injuring HUVEC can cause the changes of HUVEC biomechanical properties and membrane lipid contents; HUVEC directly damage by LPS could also activate HUVEC phospholipase A₂ (PLA₂), influencing membrane lipid metabolism; LPS could directly infiltrate and intercalate HUVEC membrane, causing and membrane contents variation. Based on these experimental results, the mechanism of lipopolysaccharide infiltration VEC membrane surface in direct LPS injury was studied and analyzed in view of the cellular biomechanical mechanism.     

电活性铁氰化镍膜电极对稀土钇的电控离子分离

通过电沉积方法分别在镀铂石英晶片和铂基底上制备了电活性铁氰化镍膜,并考察了膜电极在含钇离子溶液中的电控离子交换性能. 在0.1 mol·L^-1的硝酸钇溶液中,使用循环伏安法及石英晶体微天平技术测试考察了铁氰化镍膜对钇离子的置入释放性能及对应的质量变化,同时比较了铁氰化镍膜电极在Y(NO₃)₃和Sr(NO₃)₂溶液中的电化学性能. 在0.1 mol·L^-1 [Y(NO₃)₃ + Sr(NO₃)₂]混合溶液中,通过循环伏安法分析了薄膜对Y³⁺/Sr²⁺离子的选择性. 用扫描电子显微镜观察了铁氰化镍膜的表面形貌,并通过X射线光电子能谱仪测定了膜在氧化和还原状态下的元素组成. 结果表明,铁氰化镍膜在含Y³⁺溶液中具有良好的离子交换行为,其中氧化过程薄膜质量减少,对应着钇离子的释放;还原过程薄膜质量增加,对应钇离子的置入;在0.0 V或0.9 V调控膜电极的氧化还原状态实现对钇离子的有效分离.     

Degree of aggregation of indocyanine green in aqueous solutions determined by Mie scattering

Indocyanine green in water and aqueous NaCl solutions forms large J-aggregates. The degree of aggregation is estimated by Rayleigh scattering and Mie scattering analysis. The refractive index of the aggregates responsible for scattering is deduced from an aggregate absorption cross-section spectrum using the Kramers-Kronig relations. The average degree of aggregation for indocyanine green in water is found to be of the order of 10⁷ while it rises to 10⁹ for indocyanine green in 0.01 molar aqueous NaCl solution.     

利用X射线衍射和拉曼光谱法对KCl和NaCl混合溶液微观结构的研究

利用X射线衍射法和拉曼光谱法系统研究了25 ℃下, 0-26%质量分数浓度范围内KCl和NaCl混合溶液的结构。通过分析X射线衍射法所得的混合溶液的差值结构函数F(Q)以及差值对分布函数G(r)发现,混合溶液组分中的K⁺的水化层半径及其水化数均大于Na⁺,从而揭示出常温下NaCl在水中的溶解度大于KCl的原因。在拉曼光谱的研究中,观察到溶液中水分子的四面体氢键受破坏程度随KCl浓度的增加和NaCl浓度的减少,先增大后减小,并结合X射线衍射法的结果,推断混合溶液中Na⁺对水溶液中氢键结构的破坏程度比K⁺严重,且加入适量的K⁺会使Na⁺由结构缔造者转变为打破结构者,对水溶液结构的破坏增强。