还原性电化学合成连二亚硫酸钠循环漂白杨木化机浆的研究

Studies on reductive electrochemical bleaching of aspen CMP with sodium dithionite generated in situ

使用Na2SO3发生电化学反应在线生成Na2S2O4漂白杨木化机浆,该过程发生在一个被阳离子膜隔成两部分的实验用电化学反应容器的阴极室里。探讨了Na2SO3浓度、反应温度、pH值、电流大小、浆浓等因素对纸浆白度的影响。单段漂白实验结果显示:在Na2SO3浓度为0.8mol/L、温度70℃、pH值5.0、电流强度4A、浆浓1.5%的条件下,可以得到最高11.8%ISO的白度增值,当Na2SO3浓度降到0.4～0.5mol/L时,白度增值也能保持在10.9%ISO左右。依此条件回收漂液进行循环漂白实验,纸浆白度增值能维持在10.6%ISO,此时Na2SO3的平均消耗量在6.3%左右。循环漂白法的引入大大降低了电化学生成Na2S2O4漂白法的药品消耗,使其在工业上的应用成为可能。

In this experiment aspen CMP was bleached by sodium dithionite generated in situ by electroreduction of sodium sulphite. The process was carried out in the cathode chamber of an experimental two-compartment electrochemical reactor with a cation membrane as separator. The effect of such factors as the concentration of sodium sulphite, reaction temperature, pH value, current and pulp consistencies on the pulping brightness was discussed. Results of single-stage bleaching show that the highest brightness gain （11.8%ISO） is obtained while the variation of sodium and the temperature settled at 0.8mol/L and 70℃, respectively, pH and current are 5.0 and 4.0A. The brightness gain of 10.9%ISO can also be obtained when the consumption of sodium sulphite is reduced to 0.4～0.5mol/L. The recycle bleaching process was carried out under this condition and the brightness gain of 10.6%ISO was obtained with the actual average consumption of sodium sulphite up to 6.3% on OD pulp, a lot of operation costs for sodium sulphiteand was reduced because of introduction of recycle bleaching process. It is possible to apply recycle bleaching to industry.