Environmental Engineering Reference
In-Depth Information
TABLE 20.1
Summary of Polymerization Techniques for Synthesis of IIPs
Polymerization Technique
Size Distribution (μm)
Components
Bulk
20-50
Monomer
Initiator
Cross-linker
Precipitation
0.3-10
Monomer
Solvent (optional)
Suspension
5-50
Monomer
Continuous phase (usually water)
Initiator (soluble in continuous phase)
Surfactant
Emulsion
0.1-10
Monomer
Continuous phase (usually water)
Initiator (soluble in monomer)
Stabilizer
20.3 Membrane Technology in Water Purification Works
Membranes are remarkable materials that form part of our daily lives. Their long history
and use in biological systems have been extensively studied throughout the scientiic ield.
The preparation of synthetic nanoscale membranes is, however, a more recent invention
that has received a great audience because of its applications.
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Membrane separation tech-
nologies are widely used in many areas of water and wastewater treatment. They can be
used to produce potable water from surface water, groundwater, brackish water or sea-
water, or to treat industrial wastewaters before they are discharged or reused.
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This chapter
presents an overview of the various forms of nanostructured membranes and their use to
date, particularly for the removal of heavy metals from water.
By deinition, a membrane is a thin layer of material that is capable of separating materi-
als as a function of their physical and chemical properties when a driving force is applied
across the membrane.
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Some key elements required for the design of membranes are as
follows: it must (i) allow a high lux of water being treated, (ii) have good mechanical
strength to prevent collapse of the membrane, and (iii) have good selectivity toward the
desired substances.
20.3.1 Synthesis and Preparation of Membrane Materials
Numerous methods have been used for the preparation of membranes. The preparation
process stands as the most signiicant element in membrane research since it determines
the physiochemical properties of the membrane (basic structure), which govern the mem-
brane eficiency (Figure 20.4).
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Depending on the preparation process used, the membranes can be classiied as microil-
tration (MF), ultrailtration (UF), nanoiltration (NF), or reverse osmosis (RO) membranes.
These separate molecules by size exclusion (Figure 20.5).
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