APPLICATION AND DETERMINATION OF POLYELECTROLYTES
Lawrence K. Wang, Associate Professor
Department of Mechanical Engineering
Stevens Institute of Technology
Hoboken, New Jersey 07030
Mu Hao Wang, Associate Professor
Jao-Fuan Kao, Professor and Chairman
Department of Environmental Engineering
National Cheng Kung University
Tainan, Taiwan, China
INTRODUCTION
Polymers are organic substances of high molecular weight. They can be water-
insoluble, water-soluble or water-dispersible. Water-insoluble polymers include plastic
substances, resins, solid foams (e.g., sponge-type materials), etc. Water-soluble and water-
dispersible polymers, often in the molecular weight range of 1 to 10 million, are
particularly useful for water quality control [1,2]. According to the charge conditions,
there are three types of water-soluble and water-dispersible polymers: nonionic, anionic,
and cationic [3]. Nonionic polymers do not form ions in an aqueous medium and are
characterized by carboxylic acid amide, hydroxy, hydroxyalkyl ether and/or alkoxy
groups. In aqueous medium anionic polymers form organic anions, as from a carboxylic
acid group   while cationic polymers form organic cations, as from a pyridine group.
Ionic polymers are also called polyelectrolytes [4]. This paper reviews various applications of water-soluble and water-dispersible polymers in the fields of environmental,
chemical and biomedical engineering. A new test method for the determination of
anionic and cationic polyelectrolytes is also introduced and experimentally evaluated.
APPLICATIONS OF WATER-SOLUBLE AND WATER-DISPERSIBLE
ORGANIC POLYMERS
Water Quality Control and Sludge Treatment
Small colloidal particles in the natural system, process waters, and industrial effluents
generally bear charges; thus, they can most readily be neutralized and coagulated by
treatment with oppositvely charged polyelectrolytes. Subsequent absorption of the colloidal particles occurs on a large surface of the ionic polyelectrolyte, the treated particles are visible large floes which separate out more readily than in the case of inorganic
electrolytes [5-9].
For water quality control, the physical-chemical techniques available for floc-water
separation include sedimentation, sand filtration, diatomaceous earth filtration, ultrafiltration, reverse osmosis, flotation, centrifugation, etc. The role of a polymer in water
and wastewater treatment can be: (a) a coagulant, a flocculant, or a coagulant aid if
sedimentation is used; (b) a filter aid if sand filtration, diatomaceous earth filtration
or ultrafiltration is used; (c) a R.O. aid if reverse osmosis is used; (d) a flotation aid
if flotation is used; and (e) a centrifuge aid if centrifugation is used.
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