Ultrafiltration retention data

Table 13.8 Comparison of laboratory and environmental ultrafiltration retention data for 137Cs...

Fig. 3.6. Percentage of retention of proteins by ultrafiltration membranes. (Data according to Millipore/Amicon application note)...

Table 13.7 Comparison of retention data for an environmental sample using different ultrafiltration methods...

Membrane Pore Diameter or Molecular Weight Cutoff. The value of membrane pore diameter will have a major influence on the permeation and separation characteristics for most process filtration applications. The intrinsic membrane permeability is related to the pore diameter for many microfiltration membranes whereas, for ultrafiltration membranes, it is typically indicative of the solute retention properties. Tables 8 and 9 provide typical permeability and retention data for many common MF and UF membranes, respectively.f t ... 

Equations (22-86) and (22-89) are the turbulent- and laminar-flow flux equations for the pressure-independent portion of the ultrafiltration operating curve. They assume complete retention of solute. Appropriate values of diffusivity and kinematic viscosity are rarely known, so an a priori solution of the equations isn t usually possible. Interpolation, extrapolation, even prediction of an operating curve may be done from limited data. For turbulent flow over an unfouled membrane of a solution containing no particulates, the exponent on Q is usually 0.8. Fouhng reduces the exponent and particulates can increase the exponent to a value as high as 2. These equations also apply to some cases of reverse osmosis and microfiltration. In the former, the constancy of C aji may not be assumed, and in the latter, D is usually enhanced very significantly by the action of materials not in true solution. 

Ultrafiltration installations often produce retentates that need further processing to be marketed (e.g. spray drying). Thus, objective functions based on profit are not appropriate in ultrafiltration processes as revenue data are not generally available. Therefore, the objective function proposed in this study is the total hourly cost (to be minimised). 

Figure 14 Total turnover number (ttn) as a function of the ratio of substrate/coenzyme concentration and coenzyme retention for the enzymatic synthesis of L-terf-leucine. The data points are experimental values (compare Table 5). Feed concentrations 2-oxo-3,3-dimethylbutanoic acid (A) 500 mmol/L, (B) 900 mmol/L, (C) 500 mmol/L NAD (A) 0.06 mmol/L, (B) 0.2 mmol/L, (C) 0.2 mmol/L. UF, ultrafiltration NF, nanofiltration R, retention.

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