纸浆氧漂过程中金属离子的作用与控制

The Action and its Control of Metal Ions on Pulp Oxygen Bleaching

纸浆中金属离子主要来源于原料、处理设备、生产用水和所添加的化学药品.其中,过渡金属离子如Cu2+、Fe3+、Mn2+等会直接影响未漂浆白度,同时在纸浆氧漂过程中会催化自由基反应,导致碳水化合物降解,降低漂浆强度和粘度.Mg2+等碱土金属离子对碳水化合物具有保护作用,但也会稳定木素.对纸浆进行漂前预处理可以控制过渡金属离子的不利影响.

The metal ions in pulp result from material ,equipment , water and additional chemical agents. The transition metal ions, such as Cu 2+ 、 Fe 3+ 、 Mn 2+ , not only effect the brightness of unbleached pulp, but also catalyze the radical reaction during oxygen bleaching. With the poor selectivity, hydroxy radicals would cause an obvious degradation of carbohydrates,and decrease the strength and viscosity of oxygen bleached pulp. On the other hand , Mg 2+ can protect the carbohydrates from degradation,but at the same time ,it could stabilize the lignin. By means of pretreatment with sulfuric acid or chelating agents, we can lower the influence of the transition ions on oxygen bleaching of pulp.