过渡金属离子对辐射松硫酸盐浆氧脱木素的影响

Effect of Transition Metal Ions on the Oxygen Delignification of Radiata Pine Kraft Pulp

为了进一步了解过渡金属离子对纸浆氧脱木素过程的影响和硫酸镁作为纤维素保护剂的作用机制,本研究在辐射松硫酸盐纸浆中添加Mn2+、Fe3+和Cu2+等过渡金属离子,考察在辐射松硫酸盐浆氧脱木素过程中过渡金属离子对木素脱除率、黏度降低率、脱木素选择性及硫酸镁助剂保护作用的影响。研究结果表明:在辐射松硫酸盐浆氧脱木素过程中,不管是否存在硫酸镁助剂,过渡金属离子不影响辐射松硫酸盐浆木素的脱除;纸浆中存在的过渡金属离子会加速纸浆纤维素的降解,降低纸浆的黏度;硫酸镁助剂除了和碱反应产生不溶于水的氢氧化镁,通过吸附或形成配位化合物使过渡金属离子失去活性的作用机制之外,还存在着其他作用机理起着保护纤维素的作用。

There is a relationship between the transition metal ions in pulp and the selectivity of oxygen delignification since the transition metal ions catalyze the decomposition of hydrogen peroxide formed during the reduction of oxygen and lead to generation of hydroxyl and oxyl anion radicals which degrade cellulose. To better understand the effect of the transition metal ions on the oxygen delignification and the possible protective mechanisms of magnesium ions as cellulose protector, in this work, the transition metal ions such as Mn2＋, Fe3＋, Cu2＊, were added to the Radiata pine kraft pulp during the oxygen delignification to investigate the effect of the transition metal ions on the delignification, viscosity reduction, selectivity and protection of MgSO4. The experimental results indicated that the delignification of Radiata pine kraft pulp was not affected by the transition metal ions whether or not the additive of MgSOa was added. The existence of the transition metal ions would accelerate the degradation of ceUulose which led to the decrease of pulp viscosity. MgSO4 reacted with NaOH to produce insoluble Mg（OH）2, which inactivates the transition metal ions by physically encapsulating them either by adsorption or by the formation of coordination complexes to protect pulp cellulose. In addition, there is other protective mechanism working to protect pulp cellulose from degradation.