Mg(OH)_2引入方式对纸浆过氧化氢漂白工艺的影响

Effect of modes introducing Mg(OH)_2 on hydrogen peroxide bleaching of pulps

引言制浆造纸工业是废水和污染物排放的重要源头之一。传统含氯漂白会产生多种难降解、对环境具有高危害的含氯有机化合物,因此它们正在被过氧化氢漂白等无氯漂白工艺所取代。纸浆中的过渡金属离子可催化过氧化氢无效分解并形成对纤维素破化性强的自由基,因此常采用漂前酸洗、螯合及漂白保护剂等来消除和抑制过渡金属离子的影响。而如何使保护剂的功效得到更好的发挥,

In this paper,the effect of modes introducing Mg（OH）2 on hydrogen peroxide（H2O2）bleaching processes was investigated for the eucalyptus kraft pulps.There are three ways to introduce Mg（OH）2 into the bleaching system,i.e.,the direct-addition,or fresh-formed Mg（OH）2 by adding magnesium sulfate into a pulp slurry pre-mixed with sodium hydroxide,or vice verse.The results showed that the particle size distributions of Mg（OH）2 were quite different for the three cases.The average particle sizes are much smaller for fresh-formed Mg（OH）2 than for direct-addition.As a consequence,the processes with fresh-formed Mg（OH）2 were proved more effective for the pulp bleaching,and there were more hydrogen peroxide found in the bleaching effluents and the favorable pulp qualities.The time-dependent pH profiles of the process effluents also indicated that the decomposition of H2O2 for direct-addition or for no addition of Mg（OH）2 was very significant,especially during the early stage of the bleaching processes.