不同酸对造纸黑液酸析效果的研究

采用酸析法从造纸黑液中分离木质素,同时去除部分COD和色度,从而完成对黑液的初步处理。实验研究了酸析的最佳pH值,并将硫酸、硝酸、盐酸、磷酸、甲酸和草酸作为酸析剂,分析其分别对黑液色度、COD的去除效果及对木质素提取的影响。介绍了通过快速消解分光光度法来测定COD值,和用分光光度法测定色度值,分别建立COD值和色度对吸光度的工作曲线,使测量更加方便高效快捷,其精确度和准确度都能符合分析方法要求。实验结果表明,酸析效果较好的pH取值范围为2～4,考虑用酸的经济性和处理效果,选择pH=3作为最佳酸析条件;经过对酸析过程规律和原因的分析可得,硫酸、硝酸和磷酸对黑液处理效果较为理想,其中硫酸因其经济性被选为最佳,其色度、COD去除率分别为97.9%和66.1%,木质素的析出量为8.65 g/L。

Effect of Different Acids on Acidolysis of Black Liquid from Paper Making

Acidolysis was adopted to separate the lignin from the black liquid of paper making and partially remove COD and chroma, so as to fulfill the primary treatment of black liquid. The optimal pH for acidolysis was studied and the acids such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, formic acid and oxalic acid were used to analyze their effects on removal of chroma and COD of the black liquid and lignin extraction from it. Applying fast digestion spectrophotometry to determine COD and applying spectrophotometry to determine chroma were introduced respectively. The working curves of COD and chroma vs. absorbance were established respectively so as the determination became more convenient, faster and more efficient and the precision and accuracy became better to meet the requirements of the analysis method. The result showed that the favorite pH value of acidolysis ranged in 2 ~ 4, while considering the economy and effect, 3 was adopted as the optimal pH value. By analysis of the acidolysis process, the acids of sulfuric acid, nitric acid and phosphoric acid had good treating effects, of which the sulfuric acid was selected as the optimal one due to the economic consideration. Its removals of chroma and COD were 79. 9 and 66. 1% respectively and the lignin extraction rate was 8.65 g/L.