A brief review of the chemistry of peroxide bleaching with Mg(OH)_2 is given, and contrasted to conventionalperoxide bleaching using sodium silicate and sodium hydroxide as the base. The results of laboratory experimentsare also presented comparing conventional and Mg(OH)_2 bleaching of TMP pulp. When both the caustic andsilicate were replaced with an optimal level of Mg(OH)_2, the pulp brightness equaled or exceeded the controlbleaching at the same peroxide charge. At equivalent brightness, the residual hydrogen peroxide in theMg(OH)_2/peroxide bleaching stage was higher than for the control caustic/silicate/peroxide bleaching and suggeststhe possibility of recycling of peroxide for greater efficiency. The Mg(OH)_2/peroxide bleaching stage also hadlower COD and lower conductivity in the filtrate.
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