THE EFFECT OF ALUM AND 2 FIXATIVES IN REDUCING SILICATE RESIDUALS IN THE WHITE WATER-SYSTEM OF A PAPER-MACHINE

The sodium silicate used in conjunction with the bleaching of mechanic al pulps has been claimed to have potentially detrimental downstream e ffects in the wet end of the paper machine. This study concerns the re moval of soluble and polymerized silicate from the white water system of a pilot paper machine, The chemicals used for this purpose were alu minium sulphate (''papermakers' alum''), a polyDADMAC-type fixative, a nd a modified starch-based fixative. It was noted that these chemicals obviously reacted differently with the soluble and polymerized silica te fractions. Normally only the concentration of soluble silicate in w hite waters is subject to analysis, The results of this study suggest that due attention should also be paid to the content of polymerized s ilicate.