Sulfurated borohydride used as bleaching chemical on a softwood TMP

We studied the bleaching potential of a highly reductive chemical: sulfurated borohydride, also known as the Lalancette’s reagent, on a spruce/fir softwood TMP. The influences of reaction time, temperature, pulp consistency and reactant concentration on pulp brightness were studied. A very fast reaction was observed, along with an adverse effect of high temperature on brightness. High reactant concentration increases brightness gain. Sulfurated borohydride was compared to sodium hydrosulfite and sodium borohydride. The Lalancette’s reagent bleaches pulp to the same level as sodium hydrosulfite, but lowers the yellowness of the pulp to a greater extent.