Aqueous-phase mass balances determination

Agitation for laboratory-scale resin preparation, drive systems, 441 Aqueous-phase mass balances, determination, 384-385 Arrhenius aaivatton parameters, calculation, 423,42 ... 

Rate of Formation of Primary Precursors. A steady state radical balance was used to calculate the concentration of the copolymer oligomer radicals in the aqueous phase. This balance equated the radical generation rate with the sum of the rates of radical termination and of radical entry into the particles and precursors. The calculation of the entry rate coefficients was based on the hypothesis that radical entry is governed by mass transfer through a surface film in parallel with bulk diffusion/electrostatic attraction/repulsion of an oligomer with a latex particle but in series with a limiting rate determining step (Richards, J. R. et al. J. AppI. Polv. Sci.. in press). Initiator efficiency was... 

Head Space Analysis. A plot of peak area as a function of concentration for aqueous solutions of MMA was found to be a straight line as shown in Figure 4. This plot provides a Henry s Law relationship between the concentration of MMA in solution and its corresponding vapor pressure. In addition to these standard systems, the vapor pressure over samples from the Lj and microemulsion phases was also determined for the 14.7 wt% SLS aqueous solution. At low concentrations, the peak area is again linearly related to MMA concentration. As the saturation point is approached, however, the peak area increases more slowly. For any of the surfactant systems, the concentration of MMA in the continuous aqueous phase can be determined by constructing a horizontal line from the surfactant curve to the standard curve and then dropping a vertical line down to the concentration axis. The intercept is the concentration in the continuous phase and the amount of MMA in the micellar phase then follows from mass balance. Figure 4 shows that the concentration of MMA in the aqueous phase at the L j phase boundary and in the microemulsions is approximately 0.15 M. This is also the solubility limit of MMA in water. 

In the manufacture of aniline from nitrobenzene the reactor products are condensed and separated into an aqueous and organic phases in a decanter. The organic phase is fed to a striping column to recover the aniline. Aniline and water form an azeotrope, composition 0.96 mol fraction aniline. For the feed composition given below, make a mass balance round the column and determine the stream compositions and flow-rates. Take as the basis for the balance 100 kg/h feed and a 99.9 percentage recovery of the aniline in the overhead product. Assume that the nitrobenzene leaves with the water stream from the base of the column. 

For determination of phenol distribution coefficients the extraction proceeded for 15 minutes in order to reach equilibrium. The time required to reach equilibrium was determined by making five replicate injections of the headspace onto the SFC system. The first injection was after the extraction had proceeded for 15 minutes at 50°C and 100 atm. Following the equilibration time, four further injections at ten minute intervals were made, after which the pressure inside the extraction apparatus was increased and the system was again allowed to equilibrate (i.e. 15 minutes). The five replicate injection process was then repeated. The amount of phenol in each injection was then noted by referring to an external phenol standard calibration curve. As the total volume of the system was known, the amount of phenol in the SF could be calculated. The amount of phenol in the aqueous phase could then be calculated by mass balance. 

Purposes Can calculate the partitioning of an element between different aqueous species and complexes (inorganic and organic) and determine whether a water is supersaturated or undersalu-rated with respect to various minerals or gas phases (useful in testing mass-balance models). 

Observations Speciation models are useful for determining the relative importance of individual aqueous complexes and the toxicity of contaminated waters. They can establish whether a water has the potential to precipitate or dissolve a mineral or gas phase and whether or not various mass transfer processes such as ion exchange have the potential to affect the concentrations of various constituents. They are often used in conjunction with mass-balance models. 

Such phenomena dictated two major philosophies for our work with pyrethroids (a) a mass balance approach was taken to account for all losses in the experiments (b) as long as the pyrethroids maintained their chemical integrity (did not hydrolyse or otherwise degrade) then use of radiolabelled analytes was desirable. This allowed the low concentrations of the pyrethroids in the aqueous phase to be accurately and reproducibly determined and the mass balance to be computed. The chemical integrity of the radiochemicals was determined by radio-chromatographic techniques (radio-TLC and radio-HPLC). 

The source phase was an aqueous solution of Co(II), Cu(II), Ni(II), or Zn(II) sulfate. Concentrations of metal cations in the source phase were 0.005-0.010 M. The receiving phase was 1.0 M sulfuric acid. Samples (0.10 ml) of the aqueous phases were periodically removed for determination of the transition metal cation concentrations by atomic absorption spectroscopy. Concentrations of metal in the organic membrane phase were calculated by mass balance. The source and receiving phase volumes were maintained by addition of 0.10 ml of the appropriate initial aqueous solutions each time that samples were removed. 

In addition to extractive reaction, mass transfer is another important influence factor in the extraction process. When the mass transfer reached a stable state, the whole systems can keep a dynamic balance. The mass transfer happened between the aqueous phase and ILs, and the extraction kinetics interface of RE"" (n = 3 or 4) in ILs was shown in Fig. 5.6. Because the mass transfer rate also affects the extraction rate, the rate of RE " extraction is determined both by the chemical reaction rate and the mass transfer rate. Which one is more important in the two main factors is up to the experimental conditions. 

After completion of the experiments, the mass balance for each system was evaluated by summation of the mineralized C02, the aqueous phase organics, the extractable and inunobilized organics, and the radioactivity associated with the reactor components. Glass reactor components were extracted with methanol. Other components were combusted in order to determine associated radioactivity. In all cases, the total radioactivity associated with the aqueous phase and the reactor components was between 3-5% of the initial radioactivity. In each system, there was a fraction of unrecovered radioactivity approximately equal to the amount mineralized. Experiments were conducted using labeled sodium bicarbonate to test the NaOH capture efficiency this was found to be above 98%. Therefore, we hypothesize that the unrecovered radioactivity was lost through volatile metabolites that were not captured by the NaOH filled center well. In this case, the unrecovered would also represent bioavailable phenanthrene. 

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