采用氯化钙预处理碱法麦草浆黑液的研究

Pretreatment of soda straw pulp black-liquor with calcium chloride

碱法麦草浆黑液具有硅含量高、pH高、木素及有机物含量高等特点。木素是导致黑液色度和COD的主要原因。木素中各种复杂稳定的键型和结构单元,属难降解有机化合物。采用CaCl2对碱法麦草浆黑液进行预处理,可沉淀黑液中的SiO32-,与之生成难溶于水的CaSiO3;同时,可置换出与木素结合的Na+,形成溶解度较低的钙木素或螯合物而沉淀出来;还可与黑液中其他有机物结合。实验结果表明,采用CaCl2除硅和分离木素的同时,黑液COD明显降低,颜色由原来的深黑色变为处理后澄清的淡黄色,而碱损失较小。

Soda straw pulp blackliquor is characteristic of its high silica content, high pH values, high concentrations of lignin and high organic pollutant content. Amongst them, lignin is primarily responsible for its color and chemical oxygen demand (COD). Lignin is nonbiodegradable due to its composition of various stable chemical bonds and structure units. In this study pretreatment of soda straw pulp blackliquor with CaCl2 is investigated. It is found that CaCl2 could combine readily with SiO32- to precipitate as CaSiO3. CaCl2 could displace Na+ in sodium lignin to form insoluble calcium lignin. CaCl2 could also combine with other organic pollutants in the blackliquor. With the removal of silica and the separation of lignin, the COD of the wastewater decreases sharply and the color changes from dark black to light yellow. Soda loss is considerably low during the process.