Mini-Encyclopedia of Papermaking Wet-End Chemistry
Part Two: Definitions and Concepts

Charge

The word "charge" can be used in two ways. In its broader sense, the word refers to the sign of the net electrical potential at the surface. For example, it is accurate to say that a clay particle has a negative charge. In its narrower sense the word "charge" refers to colloidal charge demand, the number of net charge equivalents that can be consumed per unit volume or mass of sample (e.g. 4.3 microequivalents per liter). A titration procedure is required to determine the charge demand of a process sample. The total surface charge of a papermaking fibers suspended in distilled water can be determined by titration with acid or base, starting at a pH value near to 2.5, where zeta potential equals zero. The external charge demand (which is sometimes taken as an estimate of external surface charge) of papermaking materials from a paper mill process stream can be estimated by titration with a polyelectrolyte - realizing that molecular mass determines which of the pores are accessible during the titration.

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This page is maintained by Martin hubbe, Associate Professor of Wood and Paper Science, NC State University, m_hubbe@ncsu.edu .