Pressure-jump relaxation

Knoche W and Wiese G 1976 Pressure-jump relaxation techniques with optical detection Rev. Sc/. Instrum.47 220-1... 

The second method for the study of relaxation in spin-state equilibria makes use of the rapid change of pressure. Single-step pressure-jump relaxation requires an observation time of about lO s which is too slow. However, the... 

The Heterogeneous Case. Hachiya et al. (1984) and Hayes and Leckie (1986) used the pressure-jump relaxation method to study the adsorption kinetics of metal ions to oxide minerals. Their results support in essence the same adsorption mechanism as that given for homogeneous complex formation. 

Hayes and Leckie (1986) postulate on the basis of their pressure jump relaxation experiments on the adsorption-desorption of Pb2+ at the goethite-water interface the following mechanism ... 

Based on the pressure-jump relaxation results reported here, the following mechanism is postulated for the adsorption/desorption of Pb2+ ion at the goethite/water interface (8) ... 

A possible explanation for the preference of living systems for the L (levorotatory) over the D (dextrorotatory) optical isomer may be associated with the stereoselective properties of layered minerals. To test this hypothesis, the rates of L- and D-histidine intercalation into HT layered compound was investigated using the pressure-jump relaxation technique (21). The rate constants and interlayer spacing based on this investigation are summarized in Table V. As shown the slightly enhanced rate for L-histidine suggests that relative chemical reactivity may be associated with natural selection of the L-form of amino acids in nature. 

Another method to determine time-dependent properties is pressure jump relaxation. In a simple equilibrium between two states A and X,... 

Adsorption and desorption reactions of protons on iron oxides have been measured by the pressure jump relaxation method using conductimetric titration and found to be fast (Tab. 10.3). The desorption rate constant appears to be related to the acidity of the surface hydroxyl groups (Astumian et al., 1981). Proton adsorption on iron oxides is exothermic potentiometric calorimetric titration measurements indicated that the enthalpy of proton adsorption is -25 to -38 kj mol (Tab. 10.3). For hematite, the enthalpy of proton adsorption is -36.6 kJ mol and the free energy of adsorption, -48.8 kJ mol (Lyklema, 1987). 

S. Ainsworth, C.C. (1997). Arsenate and chromate retention mechanism on goethite. 2 Kinetic evaluation using a pressure-jump relaxation technique. Envir. Sci. Techn. 31 321-326... 

Zhang, P.C. Sparks, D.L. (1989) Kinetics and mechanism of molybdate adsorption/desorp-tion at the goethite/water interface using pressure-jump relaxation. Soil Sci. Soc. Am. 

Zhang, P.C. Sparks, D.L. (1990) Kinetics and mechanism of sulfate adsorption and desorption on goethite using pressure jump relaxation. Soil Sci. Soc. Am. J. 54 1266-1273 Zhang, P.C. Sparks, D.L. (1990) Kinetics of selenate and selenite adsorption/desorption at the goethite/water interface. Environ. Sci. Technol. 24 1848-1856... 

The apparatus s step change from ambient to desired reaction conditions eliminates transport effects between catalyst surface and gas phase reactants. Using catalytic reactors that are already used in industry enables easy transfer from the shock tube to a ffow reactor for practical performance evaluation and scale up. Moreover, it has capability to conduct temperature- and pressure-jump relaxation experiments, making this technique useful in studying reactions that operate near equilibrium. Currently there is no known experimental, gas-solid chemical kinetic method that can achieve this. 

Harada, S. and Schelly, Z. A. (1982). Reversed micelle of dodecylpyridinium iodide in benzene. Pressure-jump relaxation kinetic and equilibrium study of the solubilization of 7,7,8,8-tetracyanoquinodimethane. J. Phys. Chem., 86, 2098-102. 

Oxovanadium(IV) sulfate solutions were studied by Ducret who concluded that [VO(S04)] and [V0(S04)2]2- form and reported [V0S04]/([V02+][S04-]) = 63.466 Others obtained 2.4 x 102.565 Pressure jump relaxation techniques on VOS04 solutions were explained according to equation (43) K = (3.0 0.5) x 102. Grigor eva studied vanadium(lV) solutions over a wide range of H2S04 and SO2- concentrations.567... 

To study rapid reactions, traditional batch and flow techniques are inadequate. However, the development of stopped flow, electric field pulse, and particularly pressure-jump relaxation techniques have made the study of rapid reactions possible (Chapter 4). German and Japanese workers have very successfully studied exchange and sorption-desorption reactions on oxides and zeolites using these techniques. In addition to being able to study rapid reaction rates, one can obtain chemical kinetics parameters. The use of these methods by soil and environmental scientists would provide much needed mechanistic information about sorption processes. 

Methods such as nuclear magnetic resonance (NMR), electron spectroscopy for chemical analysis (ESCA), electron spin resonance (ESR), infrared (IR), and laser raman spectroscopy could be used in conjunction with rate studies to define mechanisms. Another alternative would be to use fast kinetic techniques such as pressure-jump relaxation, electric field pulse, or stopped flow (Chapter 4), where chemical kinetics are measured and mechanisms can be definitively established. 

Another consideration in choosing a kinetic method is the objective of one s experiments. For example, if chemical kinetics rate constants are to be measured, most batch and flow techniques would be unsatisfactory since they primarily measure transport- and diffusion-controlled processes, and apparent rate laws and rate coefficients are determined. Instead, one should employ a fast kinetic method such as pressure-jump relaxation, electric field pulse, or stopped flow (Chapter 4). 

Conductivity and Optical Detection Using p-Jump Relaxation 75 Evaluation of p-Jump Measurements 76 Commercially Available p-Jump Units 78 Application of Pressure-Jump Relaxation Techniques to Soil Constituents 81 Stopped-Flow Techniques 91 Introduction 91... 

Pressure-jump relaxation methods (Takahashi and Alberty, 1962 Eigen and DeMaeyer, 1963 Hoffman et al., 1966 Knoche, 1974 Gruenewald and Knoche, 1979 Yasunaga and Ikeda, 1986) and theory (Takahashi and Alberty, 1969 Bernasconi, 1976) have been reviewed extensively, and the reader is referred to these references for in-depth discussions. The p-jump methods are based on the fact that chemical equilibria are dependent on... 

Figure 4.5. Block diagram of pressure-jump relaxation apparatus with digitizing interface. [From Krizan and Strehlow (1974), with permission.]...

Application of Pressure-Jump Relaxation Techniques to Soil Constituents... 

Figure 4.9. (a) Typical relaxation curve observed by using the pressure-jump relaxation... 

Ikeda, T., Sasaki, M., Astumian, R. D., and Yasunaga, T. (1981). Kinetics of the hydrolysis of zeolite 4A surface by the pressure-jump relaxation method. Bull. Chem. Soc. Jpn. 54, 1885-1886. 

Knoche, W., and Wiese, G. (1974). An improved apparatus for pressure-jump relaxation measurements. Chem. Instrum. (N.Y.) 5, 91-98. 

Macri, G., and Petrucci, S. (1970). Pressure jump relaxation kinetics of magnesium(II), manganese(II), nickel(II), cobalt(II), copper(II), and zinc(II) m-benzenedisulfonates in anhydrous methanol at 25°. Inorg. Chem. 9, 1009-1014. 

The various elementary steps involved in the surface photoredox reaction, leading to dissolution of hematite in the presence of oxalate, are outlined in Figure 12.10. The two-dimensional stmcture of the surface of an iron(III) hydroxide given in this figure is highly schematic. The charges indicated correspond to relative charges. An important step is the formation of a hypothetical bidentate, mononuclear surface complex. With pressure jump relaxation technique, it has... 

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