酸析法和碱析法处理草浆造纸黑液的效果对比

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45mL/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。

Comparative Study on the Treatment of Straw Pulping Black Liquid by Acid-Precipitation and Alkali-Precipitation

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.