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The relevance of critical flux concept in the concentration of skim milk using forward osmosis and reverse osmosis

Artemi, Anna, Chen, George Q., Kentish, Sandra E. and Lee, Judy (2020) The relevance of critical flux concept in the concentration of skim milk using forward osmosis and reverse osmosis Journal of Membrane Science, 611, 118357.

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Abstract

Skim milk was concentrated at 10 °C using forward osmosis (FO), reverse osmosis (RO) and pressure-assisted forward osmosis (PAFO). A pressure of 40 bar, in the form of draw solution osmotic pressure (FO and PAFO modes) or transmembrane hydraulic pressure (RO mode) was applied; an additional hydraulic pressure of 2 bar was applied in the PAFO mode. More severe protein fouling was observed in RO, followed by PAFO and then FO. This was credited to the difference in the initial permeate flux, induced by the different effective driving pressures, with RO having a greater deviation of the initial flux from the critical flux value. The critical flux was determined for the FO and RO modes using a step-wise increase of draw solution osmotic pressure or hydraulic pressure, at a constant milk solids content. The critical flux was between 5.4 L/m2h (1.5 × 10−6 m3/m2s) and 7.2 L/m2h (2 × 10−6 m3/m2s) for both the FO and RO modes at a cross flow velocity of 0.2 m/s. The similarities in the critical flux for FO and RO suggests that the critical flux does not depend on the nature of pressure applied on the system (hydraulic or osmotic). Therefore, when operated at the same flux and crossflow velocity, FO would not fundamentally provide a lower fouling environment compared to RO. An increase of the solids content from 8.7% to 17.3% caused a reduction in the critical flux from 5.4 L/m2h to 3.1 L/m2h (8.5 × 10−7 m3/m2s).

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Chemical and Process Engineering
Authors :
NameEmailORCID
Artemi, Anna
Chen, George Q.
Kentish, Sandra E.
Lee, Judyj.y.lee@surrey.ac.uk
Date : 9 June 2020
Funders : Cyprus State Scholarship Foundation
DOI : 10.1016/j.memsci.2020.118357
Copyright Disclaimer : © 2020 Elsevier B.V. All rights reserved.
Uncontrolled Keywords : Dairy concentration; Protein fouling; Pressure-assisted forward osmosis; Hydraulic pressure; Osmotic pressure;
Additional Information : Embargo OK Metadata OK No Further Action
Depositing User : James Marshall
Date Deposited : 20 Jul 2020 10:44
Last Modified : 20 Jul 2020 10:44
URI: http://epubs.surrey.ac.uk/id/eprint/858244

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