In a typical PEUF process, the heavy metals in the aqueous
stream can be attached to water-soluble polymers by coordination
bonds, forming macromolecular metal-coordinated compounds
with sizes much larger than the molecular weight cut-off (MWCO)
of ultrafiltration membranes [12,19]. As a result, such macromolecules
will be retained by the membrane, thereby separating
the metals from water. The water-soluble polymer, which is a
key component in PEUF, should meet the following three general
requirements: (i) a large number of chelating units or complexforming
groups, (e.g., amino, imino, carboxyl and sulfonic acid
groups) in the macromolecule, (ii) a sufficiently high solubility in aqueous solutions, and (iii) a molecular weight greater than the
MWCO of the ultrafiltration membranes used [12].