Solution-phase concentrations

Near and Mid infrared spectroscopy can be used to monitor crystal form and polymorphic transformations, as well as solution phase concentration. 

Allows the solution phase concentration and degree of supersaturation to be monitored. 

Irrespective of the sources of phenolic compounds in soil, adsorption and desorption from soil colloids will determine their solution-phase concentration. Both processes are described by the same mathematical models, but they are not necessarily completely reversible. Complete reversibility refers to singular adsorption-desorption, an equilibrium in which the adsorbate is fully desorbed, with release as easy as retention. In non-singular adsorption-desorption equilibria, the release of the adsorbate may involve a different mechanism requiring a higher activation energy, resulting in different reaction kinetics and desorption coefficients. This phenomenon is commonly observed with pesticides (41, 42). An acute need exists for experimental data on the adsorption, desorption, and equilibria for phenolic compounds to properly assess their environmental chemistry in soil. 

Synergism in surface tension reduction efficiency. The efficiency of surface tension reduction by a surfactant is defined (9) as the solution phase concentration required to produce a given surface tension (reduction). Synergism in this respect is present in a binary mixture of surfactants when a given surface tension (reduction) can be attained at a total mixed surfactant concentration lower than that required of either surfactant by itself. This is illustrated in Figure 2. 

For example, with a Henry s law constant for HONO of 49 M atm-1, a gas-phase concentration of 1 ppb would result in a solution-phase concentration of only 4.9 X 10-8 mol L-1, compared to an anticipated H202 solution-phase concentration of 10-4 mol L-1 at the same gas-phase concentration. The rate constants also favor the H202 reaction at a pH of 3.0, that for oxidation of H202 is approximately a factor of 104 larger than that for reaction with HONO. Thus, the combination of concentrations and rate constants makes HONO unlikely to be a significant S(IV) oxidant in solution unless other oxidants such as O-, or H202 are absent. 

Therefore, based on available literature, the following sorption results were expected (l) as a result of the smectite minerals, the sorption capacity of the red clay would be primarily due to ion exchange associated with the smectites and would be on the order of 0.8 to I.5 mi Hi equivalents per gram (2) also as a result of the smectite minerals, the distribution coefficients for nuclides such as cesium, strontium, barium, and cerium would be between 10 and 100 ml/gm for solution-phase concentrations on the order of 10"3 mg-atom/ml (3) as a result of the hydrous oxides, the distribution coefficients for nuclides such as strontium, barium, and some transition metals would be on the order of 10 ml/gm or greater for solution-phase concentrations on the order of 10 7 mg-atom/ml and less (U) also as a result of the hydrous oxides, the solution-phase pH would strongly influence the distribution coefficients for most nuclides except the alkali metals (5) as a result of both smectites and hydrous oxides being present, the sorption equilibrium data would probably reflect the influence of multiple sorption mechanisms. As discussed below, the experimental results were indeed similar to those which were expected. 

Distribution Coefficients. The distribution coefficients determined for rubidium (at ll C) and for cesium (at ll C for -log Ci less than 5 and at for -log greater than 5) are summarized in Figure 1. Over the range of solution-phase concentrations in which both rubidium and cesium were studied, the rubidium coefficients appear to behave very similarly to those for cesium. For solution-phase concentrations on the order of 10 3 mg-atom/ml, the coefficients are on the order of 100 ml/gm, as was expected. Furthermore, the distribution coefficients obtained for cesium generally appear consistent with the corresponding coefficients obtained for similar oceanic sediments and related clay minerals found within the continental United States (6,7,8,9510,12,13). In the pH range of 6.3 to 8.0, the cesium coefficients appear to... 

But, the values of Ci calculated only from changes in solution-phase concentrations would be less than or equal to the actual values of Ci when strontium or barium was initially present in the clay. The uncorrected values of C should, therefore, represent minimum values for the actual solution-phase concentrations. 

For the nuclides studied (rubidium, cesium, strontium, bariun silver, cadmium, cerium, promethium, europium, and gadolinium) the distribution coefficients generally vary from about 10 ml/gm at solution-phase concentrations on the order of 10 mg-atom/ml to 10 and greater at concentrations on the order of 10 and less. These results are encouraging with regard to the sediment being able to provide a barrier to migration of nuclides away from a waste form and also appear to be reasonably consistent with related data for similar oceanic sediments and related clay minerals found within the continental United States. 

There should be good control of the bulk solution phase concentrations, ideally with constant conditions being maintained this is usually best achieved in a flow system. 

For nonlinear isotherms, the Freundlich model most often is used to describe the relationship between the sorbed (Cs) and the solution phase concentrations (Cw) ... 

Figure 6.7. Phenanthrene sorption kinetics on a sediment, where p is the sediment/water ratio, P is the solution-phase pollutant concentration, and Pe is the equilibrium solution-phase concentration of the pollutant. [From Karickhoff (1980), with permission.]...

The latter process seems to be very selective against alkali metal cations in the initial stages of exchange and is critically dependent on alkali metal solution phase concentration. Sometimes ion-exchange processes can be described as ion sieving when a particular cation (hydrated or unhydrated) is too large to enter all, or part of, the zeolite internal structure. 

There are two dependent variables in the separator the solution phase concentration (c) and the solution phase potential (O2). The solution phase concentration is governed by the material balance for lithium in the solution phase of the separator ... 

There are numerous advantages of using continuum models. They are widely used for system design and optimization. Continuum models tell us important information about the system, e g., discharge curves, state-of-health of the battery, cycle life behavior and subsequently capacity fade rate, etc. Battery models are also useful in predicting non-measurable internal variables such as solution phase concentration, solid phase concentration etc. This can be used to observe or measure buildup or loss of a certain chemical species within the domain of the battery and can be used efficient-... 

For example, if the reaction controlling the sorption of each molecule of a contaminant is identical and the capacity of a sorbent for these molecules is operationally limitless, a linear isotherm relationship is prescribed in which the sorbed-phase concentration is a constant proportion of the solution-phase concentration. When the sorption reactions are identical but sorption capacity is limited, an asymptotic approach to a maximum sorbed-phase concentration might be expected. These two limiting-condition models have been described and compared with others for description of the sorption of hydrophobic contaminants on a variety of natural soils, sediments, and suspended solids... 

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