Reverse Osmosis of Model Food Systems: Performance and Mass Transfer Characteristics (Membrane, Hyperfiltration)
Nichols, Debra Joyce
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https://hdl.handle.net/2142/70081
Description
Title
Reverse Osmosis of Model Food Systems: Performance and Mass Transfer Characteristics (Membrane, Hyperfiltration)
Author(s)
Nichols, Debra Joyce
Issue Date
1985
Department of Study
Food Science
Discipline
Food Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Food Science and Technology
Abstract
The exact mechanism for transport through reverse osmosis membranes is still a matter of controversy. To fully describe and understand the overall processes involved, the following relationships must be defined: (1) an equation relating permeate flux to the wall or boundary layer concentration (i.e., a membrane transport equation); (2) an equation relating the boundary layer concentration to a mass transfer coefficient; and (3) a model describing the mass transfer characteristics of the system in relation to feed solution properties and fluid mechanics. An attempt to define these relationships for spiral wound modules equipped with cellulose acetate membranes was made here.
Three cellulose acetate membranes, rated at 97%, 89%, and 50% sodium chloride rejection, and three model feed solutions, including a salt, a sugar, and a protein solution, were used to study performance and mass transfer characteristics of the spiral wound module and to evaluate membrane transport models. Data sets were designated Salt-97, Salt-89, Salt-50, Sucrose-97, Sucrose-89, Sucrose-50, BSA-89, and BSA-50.
Empirical models to describe permeate flux and membrane rejection as functions of the operating parameters (pressure, flow rate, temperature, and concentration) were developed using linear regression analysis. These models illustrated the functional relationships between parameters and pinpointed important interaction effects not accounted for in theoretical models.
Sourirajan's system analysis approach, which includes the film theory for mass transport, was used to obtain mass transfer coefficents. Correlations between dimensionless transport numbers were then developed for each solution-membrane combination. For this data, pressure appeared to affect estimates of the mass transfer coefficient. In the dimensionless correlations, the exponents for the Reynolds numbers for the more open membrane were close to those predicted for turbulent flow while the exponents for the Reynolds numbers for the tighter (higher rejection) membranes were closer to those predictions for laminar flow. This suggests that membrane ultrastructure (pore size) and the corresponding mechanism for membrane transport, which are not accounted for in the film theory, are important factors in determining mass transfer characteristics. (Abstract shortened with permission of author.)
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