辐射和过氧乙酸综合预处理纸浆,改善全无氯漂白选择性

Application of photo, peracetic acid, and combination pretreatments in improving totally chlorine-free bleaching selectivity

全无氯漂白(TCF)能够很好的适应环保需要,然而,TCF漂白应用和二氧化氯漂序相比较都受到了严格的限制,TCF漂白制备的浆料可能具备较低的白度和强度性能。氧脱木素(O段)通常作为漂白段的第一阶段,因此漂序的漂白选择性影响TCF漂白性能。O段和O p段前的辐射预处理改善了漂白选择性,使得所得浆料的卡伯值减少量分别达到53.7%和59.2%,漂白选择性分别增强至1.00和0.73。红外光谱分析表明,辐射预处理能够保护纤维素,避免其中的羰基和其它物质发生反应,以此来改善漂白选择性;研究发现O段比Op段对纤维的保护作用更明显。在任何一个阶段,过氧乙酸和辐射预处理的混合应用不会进一步增加漂白的选择性。简而言之,蓝光和UV辐射处理前是否添加过氧乙酸对最终成浆表现出相似的影响;该过程所处理的浆料为普通的或者过氧化氢强化的氧脱木素浆,是否添加过氧乙酸对最终成浆性能的影响不大。

The application of totally chlorine-free bleaching （TCF） is well recognized for its environmental compatibility.However, its application is restricted in comparison to a chlorine-based bleaching sequence. TCF bleaching produces pulpwith relatively lower brightness and strength properties. Oxygen delignification （O-stage） is commonly used as a firstbleaching stage; therefore its selectivity influences TCF bleaching performance. In this study, the selectivity of the O-stageand hydrogen peroxide-reinforced O-stage （Op-stage） on tropical hardwood kraft pulp were 0.53 and 0.71, with 37.8% and55.5% kappa number （Kn） reductions, respectively. The addition of photo pre-treatment prior to the O-stage and Op-stageimproved the Kn reduction to 53.7% and 59.2%; consequently the selectivity was enhanced to 1.0 and 0.73; respectively.The Fourier transform infrared spectra showed that photo pre-treatments improved the selectivity by protecting thecellulose from carbonyl-induced degradation. This protective effect was more prominent in the O-stage than the Op-stage.However, the combination of peracetic acid and photo treatment did not further increase bleaching selectivity in eitherstage. In short, blue light and UV irradiation treatment with or without the prior addition of peracetic acid to ordinary orhydrogen peroxide-reinforced oxygen delignified pulp displayed a similar bleaching effect on the resultant pulp.