ION EXCHANGE CHARACTERISTICS OP A NEW MANGANESE OXIDE : STRUCTURAL FEATURES AND ALKALI CATION EXCHANGE

Three hydrous manganese oxides were prepared by atmospheric oxidation of the hydroxide obtained by alkali addition to MnSO₄ The obtained products appear not to have been described before and their structure is a defect one resembling that of γ-Mn₂O₃ one of the samples contain some Mn(OH)2. The product obtained with ammonia, incontradistinction.to the products prepared with NaOH, has no ion exchange properties. The oxide studied in more detail and prepared with NaOH has the chemical formula N₈₄Mn₁₇O₂₇.13 H₂O. Only some of the Na in the structure could fee exchanged with other alkali ions. Besides, the oxide seems to have exchangeable H+ that can be replaced in neutral solution by K+ and to a greater extent by Cs+ but not by Li+ or Na+.Alkali ion exchanges were found to be thermodynamically irreversible, which seems to be due to differences in the defect crystalline structures of the different alkali ion forms of the oxide. A tentative picture of ion exchange mechanisms is given.     

Synthesis,adsorption and selectivity of inverse emulsion Cd(Ⅱ) imprinted polymers

Inverse emulsion polymerization was employed to synthesize inverse emulsion Cd(II) imprinted polymers(IEII P). The morphology and functional groups of IEIIP were characterized by SEM,FTIR and TG. Static adsorption experiments and competitive adsorption test were used to evaluate the adsorption ability of IEIIP. The adsorption capacity of polymers could reach 86.7 mg·g~(-1) under the optimal adsorption conditions. The pseudo second order kinetic model and Langmuir isotherm model could be used to analyze the experimental data well. The adsorption process of IEIIP was chemical adsorption process and monomolecular type. Thermodynamic parameters showed that the adsorption process was endothermic and could occur spontaneously. The selectivity coefficients k of Cd~(2+)/Pb~(2+), Cd~(2+)/Zn~(2+) and Cd~(2+)/Cu~(2+) were 2.4998, 1.2437 and 4.6882, respectively. The proposed method provides a new thought for removing Cd(II) in water samples.     

Zn(II) ions removal from aqueous solution by Karachi beach sand, a mixed crystal systems

The aim of this research work is to investigate sorption characteristic of beach sand for the removal of Zn(II) ions from aqueous solutions. The sorption of Zn(II) ions by batch dynamic method is carried out using dilute solutions (10⁻⁴ M) of nitric, hydrochloric and perchloric acids along with deionized water and from buffers of pH 2–10. Maximum sorption is noticed from deionized water (88.3%) using 30 min shaking time. Two equations, i.e. Morris–Weber and Lagergren have been tested to track the kinetics of removal process. The Langmuir, Freundlich and Dubinin–Radushkevich (D–R) model are subjected to sorption data to estimate sorption capacity, intensity and energy. The thermodynamic parameters ΔH, ΔS and ΔG are evaluated. The influence of common ions on the sorption of Zn(II) ions is also examined. Some ions reduce the sorption while most of the ions tested have very little effect. It can be concluded that beach sand has potential to remove Zn(II) ions from aqueous solutions at very low concentrations and for the treatment of industrial effluent carrying Zn(II) ions.     

Removal of Cr (VI) from aqueous solution by newspapers

The potential to remove Cr (VI) ions from aqueous solution using newspapers was investigated in the present study. The effects of relevant parameters such as solution pH, adsorbent concentration, and reaction temperature on Cr (VI) adsorption were examined. The adsorption of Cr (VI) ions onto newspapers was found to be highly pH-dependent and the highest uptake occurred at pH 1.0. The sorption equilibrium data were correlated to the Langmuir, Freundlich, Redlich-Peterson and Dubinin-Radushkevich equations. Five different non-linear error functions were examined and the result indicated that the Freundlich and Redlich-Peterson equations better fitted the equilibrium data than Langmuir isotherm. The maximum sorption capacity was found to be 55.06 mg/g at pH 1.0, adsorbent concentration 4 g/L and reaction temperature of 30 °C. Different thermodynamic parameters viz., changes in standard free energy (ΔG⁰), enthalpy (ΔH⁰) and entropy (ΔS⁰) were also evaluated and the results show that the sorption process was spontaneous and endothermic in nature. The kinetic experimental data were well fitted by the pseudo-second order, external film diffusion and diffusion models allowing the corresponding parameters to be evaluated. The sorption capacity increased with the decrease of adsorbent concentration.     

INTERFACIAL ADSORPTION OF 2-HYDROXY-5-NONYLBENZOPHENONE OXIME IN STATIC AND VIGOROUSLY STIRRED DISTRIBUTION SYSTEMS

ABSTRACT

The interfacial adsorption of 2-hydroxy-5-nonylbenzo-phenone oxime (LIX65N) at a n-heptane/water interphase was examined under static and vigorously stirred conditions, varying the aqueous pH from 2 to 12. In static systems, the pH and the concentration dependences of the interfacial tension were analysed on the basis of the Gibbs equation. The acid dissociation equilibrium at the interface was evaluated. In vigorously stirred systems, the interfacial adsorption was observed as a reversible, reproducible decrease of the organic phase concentration in response to stirring. A Langmuir isotherm was applicable for the adsorption of neutral LIX65N in acidic condition. The greater adsorption of the anionic form of LIX65N occurring in alkaline condition required an alternative isotherm.     

Measurement of excess enthalpies using a high-pressure flow microcalorimeter and determination of binary interaction parameters for thermodynamic models

While an equation of state (EOS) plays a critical role in estimating thermodynamic properties, employing it in the determination of binary interaction parameters is extremely important. In general, these parameters can be determined from phase equilibrium data. However, data collection from experiments is a time-consuming and tedious process. In this study, after measuring the excess enthalpies of binary systems containing CO₂ by high-pressure flow isothermal microcalorimetry (IMC), we determined the EOS binary interaction parameters, specifically, the Peng-Robinson EOS binary interaction parameters. These binary interaction parameters obtained by IMC were compared with those obtained by vapor-liquid equilibrium (VLE) experiments. Hence, high-pressure flow IMC appears to be an effective method for the determination of interaction parameters that are used in the estimation of thermodynamic properties. Further, the Flory-Huggins interaction parameters of a binary mixture CO₂ containing with various mole compositions were also estimated by employing high-pressure IMC.     

热力学及热力学参数状态图在SiAlON材料合成中的应用

热力学和热力学参数状态图在材料的合成和设计中起着重要的理论指导作用。文中对其基础理论知识进行了概述,重点讲述了它们在确定碳热还原氮化法合成O’SiAlON粉及热压烧结合成βSiAlON-15R复相材料的工艺条件和温度制度中的应用,并对其应用前景进行了展望。     

Light scattering and microcalorimetry studies on aqueous solutions of thermo-responsive PVCL-g-PEO copolymers

Dilute aqueous solutions of thermo-responsive poly(N-vinyl caprolactam)-graft-polyethylene oxide (PVCL-g-PEO) copolymers were studied by light scattering and high sensitivity differential scanning microcalorimetry. These copolymers are double hydrophilic at low temperatures, but become amphiphilic upon heating the solutions above the cloud point temperature of the PVCL segments (T_CP). The self-assembly properties of the copolymers are investigated by dynamic light scattering as a function of the temperature, degree of grafting and concentration. It was found that a certain critical polymer concentration is needed for the polymers to form stable aggregates. These structures are expected to consist of a hydrophobic PVCL core, stabilized by a hydrophilic PEO shell. The size of these aggregates increases with the degree of grafting. Microcalorimetry results revealed that the grafting of PVCL with hydrophilic PEO does not influence the phase transition enthalpy of PVCL.     

A thermochemical concept-based equation to estimate waste combustion enthalpy from elemental composition

Waste combustion is an interesting alternative for waste management and energy recovery. Knowledge of the waste higher heating value (HHV) is important for judging it’s worth as fuel. This work introduces a new equation, based on thermochemical concepts, to calculate HHV from elemental composition. This equation is expressed in terms of mass percentages on a dry basis of carbon (%C), hydrogen (%H), oxygen (%O), nitrogen (%N), and sulfur (%S); the HHV is computed in MJ/kg. The equation is as follows: HHV=(1−(%H₂O/100))(−0.3708(%C)−1.1124(%H)+0.1391(%O)−0.3178(%N)−0.1391(%S)). The thermochemical concept on which this expression is based involves a wide applicability. This equation neglects the inorganic carbon, hence it is not very adequate when there is a significant concentration of it. The predictions from this approach were contrasted against those proceeding from equations currently used in combustion technology, and also against bomb calorimeter data. The new equation is clearly competitive with respect to other formulations, and it can be very helpful for presenting a waste HHV value based on different derivation suppositions.     

A MICROCALORIMETRIC METHOD TO STUDY THE EFFECT OF KANAMYCIN ON THE METABOLISM OF RECOMBINANT ESCHERICHIA COLI

A microcalorimetric technique based on the metabolic heat production from cultured cells was used to investigate the effect of kanamycin on the growth and metabolism of recombinant Escherichia coli. Power-time curves of growing recombinant Escherichia coli cell suspensions treated with different kanamycin doses were recorded and were described very accurately by the generalized logistic equation. The rate constant (k) is kanamycin concentration-dependent and the relationship between k and C (kanamycin dose) is nearly linear. The 50% inhibitory concentration IC₅₀ was 88.49 µg/mL. The experimental results revealed that high doses of kanamycin inhibited the growth of recombinant E. coli during the log phase and promoted growth during the stationary phase. These results are important for deciding the optimum kanamycin dose for the maximal synthesis of human-like collagen.     

Thermodynamic Association Behaviors of Sodium Dodecyl Sulfate (SDS) with Poly(4-vinylpyridine <Emphasis Type="Italic">N</Emphasis>-oxide) (PVPNO) at Different pH Values and Ionic Strengths

The interaction of sodium dodecyl sulfate (SDS) with poly(4-vinylpyridine N-oxide) (PVPNO) at different pH values and ionic strengths has been studied by isothermal titration microcalorimetry, electrical conductivity and turbidity measurements. The solution pH significantly effects the formation of the PVPNO/SDS complex. At pH 1.5, the polymer PVPNO is a strong polycation, and the binding is dominated by electrostatic 1:1 charge neutralization with the anionic surfactant. At pH 6 and 8, the electrostatic attraction between SDS and PVPNO is weak, and the hydrophobic interaction becomes stronger. The effect of salt concentration on the interaction of SDS and PVPNO depends on the competition between the increase of interaction and the screening of interaction. This study based on the thermodynamic process gained deep insight into the effects of pH value and ionic strength on the interaction mechanism of surfactant with polyelectrolyte. We also constructed a simple model for the interaction of PVPNO and SDS system in different solution regions.     

Room temperature ionic liquids for propyne–propylene separations: Solubility behaviors and selectivity investigation

Room temperature ionic liquids (RTILs) have been discovered as very promising media for acetylene–ethylene separation. In this work, propyne and propylene solubility behaviors in dialkylimidazolium-based RTILs bearing various kinds of anions have been investigated for the feasible extraction process of propyne from propylene mixture. Solubility–molar volume relationship supported by thermodynamic analysis indicated that physical absorption mechanism plays dominantly in determining the propylene solubility. Meanwhile, unlike the acetylene solubility, which is controlled almost exclusively by hydrogen bonding interaction (chemical interaction) between the anion of RTIL and the solute, the solubility of propyne is a result from a tradeoff between chemical and physical interactions. Generally speaking, the trend of the ideal absorption selectivity for propyne over propylene is close to the acetylene–ethylene case where the higher the hydrogen bond basicity and the smaller the molar volume of RTIL results in the greater the selectivity for propyne.     

Kinetic and equilibrium studies of Pb(II) and Cd(II) removal from aqueous solution onto colemanite ore waste

The adsorption characteristics of Pb(II) and Cd(II) onto colemanite ore waste (CW) from aqueous solution were investigated as a function of pH, adsorbent dosage, contact time, and temperature. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were applied to describe the adsorption isotherms. Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The adsorption capacity of CW was found to be 33.6 mg/g and 29.7 mg/g for Pb(II) and Cd(II) ions, respectively. Analyte ions were desorbed from CW using both 1 M HCl and 1 M HNO₃. The recovery for both metal ions was found to be higher than 95%. The mean adsorption energies evaluated using the D-R model indicated that the adsorption of Pb(II) and Cd(II) onto CW were taken place by chemisorption. The thermodynamic parameters (ΔG^o, ΔH^o and ΔS^o) showed that the adsorption of both metal ions was feasible, spontaneous and exothermic at 20-50 °C. Adsorption mechanisms were also investigated using the pseudo-first-order and pseudo-second-order kinetic models. The kinetic results showed that the adsorption of Pb(II) and Cd(II) onto CW followed well pseudo-second order kinetics.     

Design of a novel bifunctional catalyst IrFe/Al2O3 for preferential CO oxidation

In this study, a novel bifunctional catalyst IrFe/Al₂O₃, which is very active and selective for preferential oxidation of CO under H₂-rich atmosphere, has been developed. When the molar ratio of Fe/Ir was 5/1, the IrFe/Al₂O₃ catalyst performed best, with CO conversion of 68% and oxygen selectivity towards CO₂ formation of 86.8% attained at 100 °C. It has also been found that the impregnation sequence of Ir and Fe species on the Al₂O₃ support had a remarkable effect on the catalytic performance; the activity decreased following the order of IrFe/Al₂O₃ > co-IrFe/Al₂O₃ > FeIr/Al₂O₃. The three catalysts were characterized by XRD, H₂-TPR, FT-IR and microcalorimetry. The results demonstrated that when Ir was supported on the pre-formed Fe/Al₂O₃, the resulting structure (IrFe/Al₂O₃) allowed more metallic Ir sites exposed on the surface and accessible for CO adsorption, while did not interfere with the O₂ activation on the FeO_x species. Thus, a bifunctional catalytic mechanism has been proposed where CO adsorbed on Ir sites and O₂ adsorbed on FeO_x sites; the reaction may take place at the interface of Ir and FeO_x or via a spill-over process.     

Dialkoxy disulfides and their branch-bonded thionosulfite isomers

A historical review on the synthesis, physical properties and chemistry of the highly chalcogenated dialkoxy disulfides (ROSSOR) and their isomeric thionosulfites (ROS(S)OR) is provided.     

Characterization of Cationic Polyelectrolytes Adsorption to an Anionic Emulsion via Zeta-Potential and Microcalorimetry

The adsorption of cationic polyelectrolytes (PEs) onto anionic silicone emulsion droplets, suspended in a sodium chloride solution is studied via electrophoretic mobility measurements and isothermal titration calorimetry. These model systems are studied to better understand the interactions governing PE adsorption-induced emulsion flocculation, which is relevant to many industrial applications. Electrophoretic mobility measurements provide critical information for rationalizing the effect of the PE charge density on the loss of stability of silicone emulsions. The interaction strength is calculated from a Langmuir adsorption isotherm determined by a ζ-potential titration measurement. Microcalorimetry measurements independently validate the adsorption free energy. Emulsion flocculation and coacervation are observed in the visual phase behavior as well as the ζ-potential titration measurements. The effect of PE charge density shows that PE-surfactant coacervation is the driving force in these PE-emulsion systems.     

硅溶胶硅酸钾混合物微量热法研究

在25.0℃及搅拌条件下,采用等温热导微量热法研究了硅溶胶与硅酸钾的混合过程。结果表明,硅溶胶与硅酸钾混合,立刻发生了SiO2溶解和复杂的化学反应,并产生了完全不同于硅溶胶和硅酸钾的SiO2胶体粒子和化学成分以及热效应,热效应受硅溶胶所占的相对重量百分比的影响。其反应的特征是硅溶胶和硅酸钾的反应级数从低到高时刻都在快速不断交替变化;随着硅溶胶所占比例的提高,热谱曲线峰高、硅溶胶与硅酸钾的混合化学反应完全的曲线总面积(总焓变QT)和热力学焓变(ΔH)数值都表现出不断增大的趋势。