Alum can serve several
functions in papermaking. The single most important use of alum is to
precipitate rosin size on pulp fibers prior to their being formed into a sheet
of a paper. Paper is sized primarily to make it resistant to penetration by
water or aqueous liquids. For example, writing ink must not be permitted to blur
or feather when applied to writing paper. Another major product, paper bags,
must resist moisture absorption in order to retain strength.
Mills producing bleached
pulp and paper grades require high water quality. Alum is frequently used as a
coagulant to remove turbidity and color. For effluent treatment in pulp and
paper mills, alum has been highly effective as a flocculant and coagulant in
removing suspended solids and color.
in the Paper Industry Technical Paper