Membrane Bioreactors for Green Processing in a Sustainable Production System - Process Intensification for Green Chemistry - page 225

MEMBRANE BIOREACTOR
FREE BIOCATALYST

BIOCATALYTIC MEMBRANE REACTOR BIOCATALYTIC MEMBRANE REACTOR

IMMOBILIZED BIOCATALYST

a b

Entrapped biocatalyst

Gelified biocatalyst

Biocatalyst flushed along the
m embrane

Ionic binding

Adsorbtion

Cross-linking

Covalent binding

Biocatalyst segregated within the
membrane module

Bound biocatalyst

Molecular recognition

Figure 8.1 Schematic classification of (a) a membrane bioreactor and (b) a biocatalytic
membrane reactor (b).

along the membrane and (2) where the biocatalyst is confined within the membrane
module, in either the shell or the lumen space.
A typical example of the first configuration is where the initial solution contains both the
catalyst and the substrate, while the product is separated from the feed solution by the
membrane operation. This type of reactor integrates a traditional continuously stirred tank
reactor (CSTR) with a separation unit (the membrane plant).
Ultrafiltration is the most common separation process used in this kind of setup. Both
dead-end continuous stirred ultrafiltration cells with flat membranes and crossflow
ultrafiltration through tubular membrane modules have been widely investigated.
One of the main drawbacks of this configuration is concentration polarization phenomena,
which severely affect the performance of the separation process; when these occur, it is

(b)

(a)

Submerged
membrane module

External membrane
module

Figure 8.2 Schematic representation of (a) an external membrane reactor and (b) a submerged
membrane reactor. Adapted fromGiorno et al. # 2003 by permission of Wiley Periodicals, Inc.
# 2003.