酸析法和碱析法处理草浆造纸黑液的效果对比

摘要

对比了酸析法和碱析法对碱法草浆造纸黑液中木质素的去除效果,并分析了聚合氯化铝(PAC)絮凝剂对酸析和碱析后木质素的絮凝效果.实验结果表明:酸析法和碱析法都能有效析出造纸黑液中的木质素,酸析法对色度的去除效果要优于碱析法；当造纸黑液pH为3时,COD去除率达到72.0％,色度去除率为97.7％；当造纸黑液pH为13时,COD去除率达到55.0％,色度去除率为22.3％；PAC对于酸析后木质素有较好的絮凝效果,当废水温度为55℃、PAC加入量为45 mL/L时,COD去除率可以达到79.5％,色度去除率为98.5％; PAC絮凝剂对于碱析后的造纸黑液色度的去除效果较差.%The effects of acid-precipitation and alkali-precipitation on the removal of lignin from straw alkaline pulping black liquor were compared.The flocculating effects of poly aluminium chloride (PAC) on lignin after acid-precipitation and alkali-precipitation were analyzed.The experimental results show that:Both acid-precipitation and alkali-precipitation can effectively separate lignin from the black liquor,but the removal of chroma by acid-precipitation is better than that by alkali-precipitation; When the black liquor pH is 3,the removal rates of COD and chroma are 72.0％ and 97.7％ respectively; When the black liquor pH is 13,the removal rates of COD and chroma are 55.0％ and 22.3％ respectively; The PAC has a better effect on the flocculation of lignin after acid-precipitation,and when the wastewater temperature is 55 ℃ and the PAC dosage is 45 mL/L,the removal rates of COD and chroma are 79.5％ and 98.5％ respectively; The effect of PAC on the removal of lignin after alkali-precipitation is bad.